A Survey on Blockchain-Based Federated Learning:Categorization,Application and Analysis

Federated Learning(FL),as an emergent paradigm in privacy-preserving machine learning,has garnered significant interest from scholars and engineers across both academic and industrial spheres.Despite its innovative approach to model training across distributed networks,FL has its vulnerabilities;the centralized server-client architecture introduces risks of single-point failures.Moreover,the integrity of the global model—a cornerstone of FL—is susceptible to compromise through poisoning attacks by malicious actors.Such attacks and the potential for privacy leakage via inference starkly undermine FL’s foundational privacy and security goals.For these reasons,some participants unwilling use their private data to train a model,which is a bottleneck in the development and industrialization of federated learning.Blockchain technology,characterized by its decentralized ledger system,offers a compelling solution to these issues.It inherently prevents single-point failures and,through its incentive mechanisms,motivates participants to contribute computing power.Thus,blockchain-based FL(BCFL)emerges as a natural progression to address FL’s challenges.This study begins with concise introductions to federated learning and blockchain technologies,followed by a formal analysis of the specific problems that FL encounters.It discusses the challenges of combining the two technologies and presents an overview of the latest cryptographic solutions that prevent privacy leakage during communication and incentives in BCFL.In addition,this research examines the use of BCFL in various fields,such as the Internet of Things and the Internet of Vehicles.Finally,it assesses the effectiveness of these solutions.

哈密–郑州±800 kV直流输电工程换流站无功补偿研究

换流站无功补偿的研究是特高压直流设计的重要组成部分。本文以哈密–郑州±800 kV直流输电工程为例,按照相应的计算原则计算了不同运行方式下的换流站无功消耗,研究了两端换流站的无功补偿总容量和小组容量要求,在此基础上提出了换流站的无功补偿设备配置方案。

Effect of Nb on the dynamic recrystallization behavior of high-grade pipeline steels

The dynamic recrystallization （DRX） behavior of high-grade X80/X100 pipeline steels with different Nb contents was investi- gated through single pass compression experiment using a Gleeble 1500 thermomechanical simulator. By the regression of stress-sWain data obtained in the experiment, the deformation activation energy of DRX was identified, and the critical strain was calculated with the Po- liak-Jonas （P-J） method. Based on the analysis, the occurrence condition and kinetics of DRX were determined. The results show that as the Nb content increases from 0.08wt% to 0.095wt%, the activation energy of recrystallization raises from 365 to 395 kJ/mol. The critical swain of DRX can be determined more accurately by the P-J method, and the ratios of critical swain to peak sWain of XS0 and X100 pipeline steels are 0.51 and 0.49, respectively, which are similar to the results achieved by other researchers and calculated with empirical formulae.

Autonomous-synergic Voltage Security Regions in Bulk Power Systems

Determining security/stability boundaries is a common and critical means of preventing cascading failures induced by voltage-related issues,which represents one of the major challenges in bulk power systems.However,traditional approaches suffer from conservative issues and heavy computational burdens.To address these challenges,the concept of an autonomous-synergic voltage security region(AS-VSR)and the corresponding dynamic constraint coefficient pruning(DCCP)computation method,which fully consider the volt/var characteristics of bulk power systems,are proposed in this letter.Both linearized and nonlinearized robust optimization problems are introduced to obtain accurate results.The computational accuracy,time cost,and advantages of autonomous-synergic control are observed in the simulation results.

Radical Heteroarylalkylation of Alkenes via Three-Component Docking-Migration Thioetherification Cascade

A novel,rational-designed approach to access various heteroaryl-substituted alkyl thioethers was developed via docking-migration cascade process.By utilizing three components involving alkene,dual-function reagent,and thioetherificating reagent,radical heteroarylalkylation of alkenes followed by thiolation of the alkyl radical intermediates proceeded smoothly,manifesting well compatibility of substrates and cascade transformations.Furthermore,this protocol also features mild conditions,broad substrate scope,and wide product diversity.

Mixed Aleatory-epistemic Uncertainty Modeling of Wind Power Forecast Errors in Operation Reliability Evaluation of Power Systems

As the share of wind power in power systems continues to increase, the limited predictability of wind power generation brings serious potential risks to power system reliability. Previous research works have generally described the uncertainty of wind power forecast errors(WPFEs) based on normal distribution or other standard distribution models, which only characterize the aleatory uncertainty. In fact, epistemic uncertainty in WPFE modeling due to limited data and knowledge should also be addressed. This paper proposes a multi-source information fusion method(MSIFM) to quantify WPFEs when considering both aleatory and epistemic uncertainties. An extended focal element(EFE) selection method based on the adequacy of historical data is developed to consider the characteristics of WPFEs. Two supplementary expert information sources are modeled to improve the accuracy in the case of insufficient historical data. An operation reliability evaluation technique is also developed considering the proposed WPFE model. Finally,a double-layer Monte Carlo simulation method is introduced to generate a time-series output of the wind power. The effectiveness and accuracy of the proposed MSIFM are demonstrated through simulation results.

Short-term Transmission Maintenance Scheduling Considering Network Topology Optimization

With the increasing penetration of renewable energy sources,transmission maintenance scheduling(TMS)will have a larger impact on the accommodation of wind power.Meanwhile,the more flexible transmission network topology owing to the network topology optimization(NTO)technique can ensure the secure and economic operation of power systems.This paper proposes a TMS model considering NTO to decrease the wind curtailment without adding control devices.The problem is formulated as a two-stage stochastic mixed-integer programming model.The first stage arranges the maintenance periods of transmission lines.The second stage optimizes the transmission network topology to minimize the maintenance cost and system operation in different wind speed scenarios.The proposed model cannot be solved efficiently with off-theshelf solvers due to the binary variables in both stages.Therefore,the progressive hedging algorithm is applied.The results on the modified IEEE RTS-79 system show that the proposed method can reduce the negative impact of transmission maintenance on wind accommodation by 65.49%,which proves its effectiveness.

Damping forced oscillations in power system via interline power flow controller with additional repetitive control

With the continuous expansion of power systems and the application of power electronic equipment, forced oscillation has become one of the key problems in terms of system safety and stability. In this paper, an interline power flow controller (IPFC) is used as a power suppression carrier and its mechanism is analyzed using the linearized state-space method to improve the system damping ratio. It is shown that although the IPFC can suppress forced oscillation with well-designed parameters, its capability of improving the system damping ratio is limited. Thus, combined with the repetitive control method, an additional repetitive controller (ARC) is proposed to further dampen the forced power oscillation. The ARC control scheme is characterized by outstanding tracking performance to a system steady reference value, and the main IPFC controller with the ARC can provide higher damping, and further reduce the amplitude of oscillations to zero compared with a supplementary damping controller (SDC). Simulation results show that the IPFC with an ARC can not only greatly reduce the oscillation amplitude, but also actively output the compensation power according to the reference value of the ARC tracking system.

A Hierarchical Transactive Energy Management Framework for Optimizing the Reserve Profile in District Energy Systems

District energy systems(DESs)have become a popular form of satisfying comprehensive energy demands for different types of loads in multiple local buildings.For DFISs,the operational flexibility could be maintained by energy conversion and storage facilities.This paper proposes a hierarchical optimization framework for leveraging and aggregating the DES flexibility to provide contingency reserves.To characterize and quantify the flexibility in individual DESs,the concept of available reserve profile,which is measured by a set of indices,is established.A two-stage robust optimization(RO)model is developed for calculating the indices,which considers the uncertainties associated with wind power and ambient temperature.The lower stage of the two-stage model is managed by district energy system operators(DESOs)which submit reserve profiles to the district energy system coordinator(DESC)at the upper stage,which is responsible for the coordination process.Correspondingly,information privacy is preserved using a coordinated data-sharing strategy.Using reserve profiles submitted by multiple DESOs,the DESC applies the proposed coordination model to provide a certain reserve capacity schedule to DESs,which satisfies the stated objectives.The coordination model is formulated and solved based on the special ordered set(SOS)technique and particle swarm optimization(PSO)algorithm.A test system is developed to illustrate the technical viability and economic feasibility of the proposed technique.

Development and experimental characterization of a robotic butterfly with a mass shifter

The development of biomimetic aerial robots has emerged as a new solution for studying the flight mechanisms of flying creatures.This study designs a biomimetic robotic butterfly steered via a mass shift mechanism named USTButterfly-II and investigates its flight characteristics using an optical tracking facility.First,a planar fourbar linkage was used to drive the flapping of the designed butterfly-like artificial wings.Next,an innovative tailless steering control method was proposed based on a mass shift mechanism.Finally,the wing kinematics and motion trajectory of the USTButterfly-II were measured using a multi-camera motion capture system,and some difficult-to-measure flapping aerodynamic parameters,such as the instantaneous net lift and thrust coefficients,were determined.These findings present a novel experimental framework that not only provides effective data support for the design and improvement of the robotic butterfly but also benefits the study of biological butterfly flight mechanisms.