Simulation on Calculation Accuracy of Three Methods for Live Line Measuring the Parameters of Transmission Lines with Mutual Inductance

Live line measurement methods can reduce the loss of power outages and eliminate interference. There are three live line measurement methods including integral method, differential method and algebraic method. A simulation model of?two coupled parallel transmission lines spanning on the same towers is built in PSCAD and the calculation errors of these three methods are compared with different sampling frequencies by using of Matlab. The effect of harmonic on calculation is also involved. The simulation results indicate that harmonic has the least effect on the algebraic method which provides stable result and small error.

FREPD: A Robust Federated Learning Framework on Variational Autoencoder

Federated learning is an ideal solution to the limitation of not preser-ving the users’privacy information in edge computing.In federated learning,the cloud aggregates local model updates from the devices to generate a global model.To protect devices’privacy,the cloud is designed to have no visibility into how these updates are generated,making detecting and defending malicious model updates a challenging task.Unlike existing works that struggle to tolerate adversarial attacks,the paper manages to exclude malicious updates from the glo-bal model’s aggregation.This paper focuses on Byzantine attack and backdoor attack in the federated learning setting.We propose a federated learning frame-work,which we call Federated Reconstruction Error Probability Distribution(FREPD).FREPD uses a VAE model to compute updates’reconstruction errors.Updates with higher reconstruction errors than the average reconstruction error are deemed as malicious updates and removed.Meanwhile,we apply the Kolmogorov-Smirnov test to choose a proper probability distribution function and tune its parameters to fit the distribution of reconstruction errors from observed benign updates.We then use the distribution function to estimate the probability that an unseen reconstruction error belongs to the benign reconstruction error distribution.Based on the probability,we classify the model updates as benign or malicious.Only benign updates are used to aggregate the global model.FREPD is tested with extensive experiments on independent and identically distributed(IID)and non-IID federated benchmarks,showing a competitive performance over existing aggregation methods under Byzantine attack and backdoor attack.

Estimation of 1-dimensional nonlinear stochastic differential equations based on higher-order partial differential equation numerical scheme and its application

A method based on higher-order partial differential equation （PDE） numerical scheme are proposed to obtain the transition cumulative distribution function （CDF） of the diffusion process （numerical differentiation of the transition CDF follows the transition probability density function （PDF））, where a transformation is applied to the Kolmogorov PDEs first, then a new type of PDEs with step function initial conditions and 0, 1 boundary conditions can be obtained. The new PDEs are solved by a fourth-order compact difference scheme and a compact difference scheme with extrapolation algorithm. After extrapolation, the compact difference scheme is extended to a scheme with sixth-order accuracy in space, where the convergence is proved. The results of the numericM tests show that the CDF approach based on the compact difference scheme to be more accurate than the other estimation methods considered; however, the CDF approach is not time-consuming. Moreover, the CDF approach is used to fit monthly data of the Federal funds rate between 1983 and 2000 by CKLS model.

Spintronic terahertz emission with manipulated polarization (STEMP)

Highly efficient generation and arbitrary manipulation of spin-polarized terahertz(THz)radiation will enable chiral lightwave driven quantum nonequilibrium state regulation,induce new electronic structures,consequently provide a powerful experi-mental tool for investigation of nonlinear THz optics and extreme THz science and applications.THz circular dichromic spectroscopy,ultrafast electron bunch manipulation,as well as THz imaging,sensing,and telecommunication,also need chiral THz waves.Here we review optical generation of circularly-polarized THz radiation but focus on recently emerged polarization tunable spintronic THz emission techniques,which possess many advantages of ultra-broadband,high efficiency,low cost,easy for integration and so on.We believe that chiral THz sources based on the combination of electron spin,ultra-fast optical techniques and material structure engineering will accelerate the development of THz science and applications.

Long-term trends in fog and boundary layer characteristics in Tianjin,China

Long-term trends in fog episodes, vertical variations of atmospheric boundary structure, and air pollutant concentrations during two different heavy fog events in the Tianjin area were analyzed. The total amount of fog has increased since 1980 due to the stability of the boundary layer and an increase of pollutant emissions. The variation in the characteristics of the boundary layer and air pollutant concentrations were significantly different between the two fog processes （fog I and fog ll）. The onset of fog I was accompanied by a temperature inversion in the low atmosphere, and the average kinetic energy showed a clear diurnal trend and vertical variation, which increased with height. The dissipation of fog I was mainly due to turbulence. However, the atmospheric stratification was not stable in the lower layer before the onset of fog If. The diurnal and vertical changes in kinetic energy were very small, in which turbulent momentum at each measurement height tended to be zero. In the dissipation process of fogⅡ, wind speed increased significantly. Surface PM2.s concentrations decreased, but the ratio of PMzs to PM10 increased from 0.66 to 0.82 until fog I dissipated. However, the concentration of PMzs did not decrease at the early stage of fog Ⅱ, but the ratio of PM2.5 to PM10 PM2.5JPM10 decreased to 0.21 when fog Ⅱ dissipated. This study showed that there was a clear difference in the evolution of pollutant concentration for different pollutants and in different developing stages during the fog events. PM2.5 concentration accumulated faster than those of SO2 and NOx, and the PM2.5 cumulative rate was greater in the mid-term of the fog process.