default author photo

Shunli Wang

Southwest University of Science and Technology

SCHOLARLY PAPERS

39

DOWNLOADS

1,780

TOTAL CITATIONS
Rank 24,425

SSRN RANKINGS

Top 24,425

in Total Papers Citations

32

Scholarly Papers (39)

1.

An Innovative Square Root - Untraced Kalman Filtering Strategy with Full-Parameter Online Identification for State of Power Evaluation of Lithium-Ion Batteries

Number of pages: 32 Posted: 11 Jul 2024
Southwest University of Science and Technology, Inner Mongolia University of Technology, Inner Mongolia University of Technology, Inner Mongolia University of Technology, Robert Gordon University and Aalborg University
Downloads 122 (592,433)
Citation 5

Abstract:

Loading...

lithium-ion battery, state of charge, state of power, full-parameter online identification, online square root traceless Kalman, multi-constraint factor fusion analysis

2.

Remaining Useful Life Prediction and State of Health Diagnosis for Lithium-Ion Batteries Based On Improved Grey Wolf Optimization Algorithm-Deep Extreme Learning Machine Algorithm

Number of pages: 33 Posted: 21 Jun 2023
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 117 (630,858)
Citation 12

Abstract:

Loading...

lithium-ion batteries, State of Health, health indicator, grey wolf algorithm, deep extreme learning machine

3.

Remaining Useful Life Prediction and State of Health Diagnosis Of Lithium-Ion Batteries with Multiscale Health Features Based on Optimized Catboost Algorithm

Number of pages: 37 Posted: 18 Jan 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 98 (699,467)
Citation 3

Abstract:

Loading...

lithium-ion battery, remaining useful life, state of health, CatBoost, IFO-PSO-ACO

Comprehensive Multiple Time Scale Battery Charge and Health State Estimation with Improved Adaptive Forgetting Factor - Dual Adaptive Kalman Filtering for Smart Grid Energy Station

Number of pages: 25 Posted: 04 Feb 2025
Southwest University of Science and Technology, Inner Mongolia University of Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology, Robert Gordon University and Aalborg University
Downloads 52 (1,119,531)

Abstract:

Loading...

smart grid energy station, State of charge, state of health, multiple time scale estimation, adaptive forgetting factor, dual adaptive Kalman filtering

Comprehensive Multiple Time Scale Battery Charge and Health State Estimation with Improved Adaptive Forgetting Factor - Dual Adaptive Kalman Filtering for Smart Grid Energy Station

Number of pages: 25 Posted: 19 Feb 2025
Southwest University of Science and Technology, Inner Mongolia University of Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology, Robert Gordon University and Aalborg University
Downloads 24 (1,473,203)

Abstract:

Loading...

smart grid energy station, state of charge, state of health, multiple time scale estimation, adaptive forgetting factor, dual adaptive Kalman filtering

Improved 2rc-Pngv Modeling and Adaptive Sage-Husa H Infinity Filtering for Battery Power State Estimation Based on Multi-Parameter Constraints

Number of pages: 20 Posted: 19 Feb 2025
Southwest University of Science and Technology, Inner Mongolia University of Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology, Robert Gordon University and Aalborg University
Downloads 37 (1,252,562)

Abstract:

Loading...

Lithium-ion battery, Estimation strategy of SOC, Power state estimation strategy, Dynamic particle swarm optimization algorithm, H-infinity filtering, State joint estimation

Improved 2rc-Pngv Modeling and Adaptive Sage-Husa H Infinity Filtering for Battery Power State Estimation Based on Multi-Parameter Constraints

Number of pages: 20 Posted: 06 Dec 2024
Shunli Wang and Xinyu Yan
Southwest University of Science and Technology and Inner Mongolia University of Technology
Downloads 35 (1,281,607)

Abstract:

Loading...

lithium-ion battery, Estimation strategy of SOC, Power state estimation strategy, Dynamic particle swarm optimization algorithm, H-infinity filtering, State joint estimation

6.

Improved Hybrid Neural Network Based on Cnn-Bilstm-Attention for Co-Estimation of SOC and SOE in Lithium-Ion Batteries

Number of pages: 23 Posted: 04 Feb 2025
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 70 (907,769)

Abstract:

Loading...

lithium-ion battery, State of charge, State of energy, Joint estimation, Hybrid neural network

SOC Estimation of Lithium-Ion Battery Based on Optimized Bidirectional Long Short Term Memory-Multilayer Perceptron Hybrid Model at Multi-Temperature Ranges

Number of pages: 26 Posted: 29 Feb 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 40 (1,210,354)

Abstract:

Loading...

state of charge, Lithium-ion battery, BiLSTM, multiple perceptrons, particle swarm optimization algorithm, Genetic algorithm

SOC Estimation of Lithium-Ion Battery Based on Optimized Bidirectional Long Short Term Memory-Multilayer Perceptron Hybrid Model at Multi-Temperature Ranges

Number of pages: 26 Posted: 15 Jan 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 23 (1,459,262)

Abstract:

Loading...

State of charge, lithium-ion battery, BiLSTM, multiple perceptrons, particle swarm optimization algorithm, genetic algorithm

8.

A Novel Cuckoo Search Optimization Particle Filtering Strategy for the Remaining Useful Life Prediction of the Lithium-Ion Batteries in Hybrid Electric Vehicle

Number of pages: 43 Posted: 22 Mar 2022
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Southwest University of Science and Technology
Downloads 62 (942,565)

Abstract:

Loading...

battery management system, Remaining Useful Life, cuckoo search particle filter, capacity degradation, exponential growth model, resampling rate

9.

A Hybrid Neural Network Optimized by an Improved Harris Hawk Algorithm for State of Charge Estimation of Lithium-ion Batteries under Wide Temperature Environmental Conditions

Number of pages: 31 Posted: 23 Sep 2025
Inner Mongolia University of Technology, Inner Mongolia University of Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Robert Gordon University and Aalborg University
Downloads 60 (970,490)

Abstract:

Loading...

Lithium-ion battery, state of charge estimation, Differential Evolution Algorithm, Harris Hawk Optimization Algorithm, Parameter Optimization

10.

Online State of Charge Estimation for Lithium-Ion Batteries Based on Improved Fuzzy C-Means Clustering Sparrow Search Algorithm-Backpropagation Neural Network

Number of pages: 34 Posted: 28 Jul 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Aalborg University and Robert Gordon University
Downloads 56 (1,000,027)

Abstract:

Loading...

Lithium-ion batteries, State of charge, C-means clustering, sparrow search, backpropagation

11.

Joint State of Charge and State of Energy Estimation of Special Aircraft Lithium-ion Batteries by Optimized Genetic Marginalization-extended Particle Filtering

Number of pages: 27 Posted: 08 Oct 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Aalborg University and Robert Gordon University
Downloads 52 (1,052,702)

Abstract:

Loading...

Nickel cobalt manganese acid ternary lithium-ion batteries, Equivalent modeling, State estimation, Inconsistency diagnosis, Battery Management

An Enhanced Bidirectional Long Short Term Memory-Multilayer Perceptron Hybrid Model for Lithium-Ion Battery State of Charge Estimation at Multi-Temperature Ranges

Number of pages: 33 Posted: 25 Jul 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 26 (1,430,393)
Citation 1

Abstract:

Loading...

state of charge, lithium-ion battery, BiLSTM, multiple perceptrons, particle swarm optimization algorithm, genetic algorithm

An Enhanced Bidirectional Long Short Term Memory-Multilayer Perceptron Hybrid Model for Lithium-Ion Battery State of Charge Estimation at Multi-Temperature Ranges

Number of pages: 33 Posted: 30 Jul 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 23 (1,459,262)

Abstract:

Loading...

state of charge, lithium-ion battery, BiLSTM, multiple perceptrons, particle swarm optimization algorithm, genetic algorithm

13.

A Novel Online High-Precision Parameter Identification for Lithium-Ion Batteries Based on Discount Method Considering Abrupt Current Changes

Number of pages: 18 Posted: 08 Aug 2024
Runx Lin, Shunli Wang, Chunmei Yu and Liya Zhang
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Inner Mongolia University of Technology
Downloads 46 (1,109,210)

Abstract:

Loading...

Lithium-ion batteries, parameter identification, current pulse, discount method, abrupt current changes

14.

Battery Pack Capacity Estimation Based on Improved Cooperative Co-Evolutionary Strategy and Lightgbm Hybrid Models Using Indirect Health Features

Number of pages: 36 Posted: 03 Sep 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 45 (1,121,190)
Citation 1

Abstract:

Loading...

lithium-ion battery pack, capacity estimation, Health feature extraction, cooperative co-evolutionary algorithm, LightGBM

15.

An Improved Forgetting Factor - Dual Adaptive Kalman Filtering Algorithm for High-Precision Battery State of Health Estimation Suitable for Sharp Current Variation Conditions

Number of pages: 17 Posted: 04 Aug 2024
Shunli Wang and Yupeng Wang
Southwest University of Science and Technology and Inner Mongolia University of Technology
Downloads 45 (1,121,190)

Abstract:

Loading...

online parameter identification, power lithium-ion battery, offline parameter identification, equivalent circuit model, state of charge, state of health

An Improved Sparrow Search - Early Stopping Convolutional Neural Network Modeling Method for Battery State of Energy Estimation of Large Scale Energy Storage Systems

Number of pages: 25 Posted: 29 Apr 2025
Southwest University of Science and Technology, Inner Mongolia University of Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology, Robert Gordon University and affiliation not provided to SSRN
Downloads 25 (1,430,393)

Abstract:

Loading...

Power Lithium-ion Battery, State of Energy, Convolutional Neural Network, Sparrow Search Algorithm, Early Stopping Strategy

An Improved Sparrow Search - Early Stopping Convolutional Neural Network Modeling Method for Battery State of Energy Estimation of Large Scale Energy Storage Systems

Number of pages: 24 Posted: 01 Apr 2025
Southwest University of Science and Technology, Inner Mongolia University of Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology, Robert Gordon University and affiliation not provided to SSRN
Downloads 18 (1,525,626)

Abstract:

Loading...

Power Lithium-ion Battery, State of Energy, Convolutional Neural Network, Sparrow Search Algorithm, Early Stopping Strategy

17.

Comprehensive Insights into Battery State of Energy Estimation with Data Driven Strategies

Number of pages: 35 Posted: 10 Jun 2025
Southwest University of Science and Technology, Inner Mongolia University of Technology, Inner Mongolia University of Technology, Inner Mongolia University of Technology, Robert Gordon University and Aalborg University
Downloads 42 (1,170,409)

Abstract:

Loading...

State estimation of lithium-ion batteries, Kalman filtering, Equivalent modeling, Based on model estimation, State of charge, State of energy

Downloads 21 (1,486,852)

Abstract:

Loading...

Lithium-ion battery, energy state, nonlinear variation, neural network, historical state, harmonic loss

Downloads 19 (1,525,626)

Abstract:

Loading...

lithium-ion battery, energy state, nonlinear variation, neural network, historical state, harmonic loss

19.

An Improved Pelican Optimization - Kernel Extreme Learning Machine for Highly Accurate State of Charge Estimation of Lithium-Ion Batteries in Energy Storage Systems

Number of pages: 25 Posted: 23 Feb 2025
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 39 (1,196,171)
Citation 1

Abstract:

Loading...

Lithium-ion battery, State of Charge, Pelican optimization algorithm, Kernel extreme learning machine, TWCS-PO-KELM model

20.

An Improved Pelican Optimization Algorithm - Kernel Extreme Learning Machine for High Accurate State of Charge Estimation of Lithium-Ion Batteries in Energy Storage Systems

Number of pages: 23 Posted: 13 Oct 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology and Robert Gordon University
Downloads 39 (1,196,171)

Abstract:

Loading...

Lithium-ion battery, State of charge, Improved pelican optimization algorithm, Kernel extreme learning machine, IPOA-KELM model

21.

Enhancing State of Charge Prediction of Lithium-Ion Batteries Through Linear Polynomial Regression – Support Vector Machine Modeling with Temperature Varying and Open Circuit Voltage Compensation

Number of pages: 23 Posted: 18 May 2025
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology, Robert Gordon University and Aalborg University
Downloads 38 (1,209,354)

Abstract:

Loading...

Linear Polynomial Regression, Temperature Compensation, Electrochemical Dynamics, Non-linear Regression, Support Vector Machine

22.

A Novel Seeker Optimization - Particle Filtering Method for the Remaining Useful Life Prediction of Lithium-Ion Batteries Considering Capacity Recovery Effect

Number of pages: 15 Posted: 23 Mar 2022
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 38 (1,222,651)

Abstract:

Loading...

lithium-ion battery, remaining useful life, seeker optimization, particle filtering, capacity recovery effect

23.

Multiple Layer Kernel Extreme Learning Machine Modeling and Eugenics Genetic Sparrow Search Algorithm for the State of Health Estimation of Lithium-Ion Batteries

Number of pages: 30 Posted: 24 Apr 2023
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 36 (1,236,159)

Abstract:

Loading...

state of health, Multiple layer kernel extreme learning machine, Eugenics genetic sparrow search algorithm, Fusion features, Multi-indicator comparison

24.

A Novel Multiple Training-Scale Dynamic Adaptive Cuckoo Search Optimized Long Short-Term Memory Neural Network and Multi-Dimensional Health Indicators Acquisition Strategy for Whole Life Cycle Health Evaluation of Lithium-Ion Batteries

Number of pages: 27 Posted: 08 Sep 2022
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Robert Gordon University and Aalborg University
Downloads 36 (1,249,711)

Abstract:

Loading...

state of health, dynamic adaptive cuckoo search optimization long short-term memory neural network algorithm, health characteristic indexes, global search ability, battery aging

25.

An Optimized Adaptive Finite Difference-Extended Kalman Filtering Strategy for Online SOC Estimation of High Energy Density Lithium-Ion Batteries in Unmanned Aerial Vehicles

Number of pages: 27 Posted: 28 Aug 2024
Southwest University of Science and Technology, Inner Mongolia University of Technology, Inner Mongolia University of Technology, Inner Mongolia University of Technology, Robert Gordon University and Aalborg University
Downloads 35 (1,263,436)

Abstract:

Loading...

Lithium-ion batteries, State of Charge, Voltage matching, Extended Kalman filter, Self-adaptation, Finite difference

26.

An Improved Fuzzy Sliding Window - Cubature Kalman Filtering Method for Joint State of Energy and State of Charge Estimation of Urban-Public-Transportation Lithium-Ion Batteries

Number of pages: 18 Posted: 02 May 2023
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Aalborg University and Aalborg University
Downloads 33 (1,290,922)

Abstract:

Loading...

Lithium-ion battery, state of energy, State of charge, fuzzy adaptive controller, sliding window Multi-innovation

27.

Improved Volumetric Noise-Adaptive H-Infinity Filtering for Accurate State of Power Estimation of Lithium-Ion Batteries with Multi-Parameter Constraint Considering Low-Temperature Influence

Number of pages: 25 Posted: 13 Nov 2024
Southwest University of Science and Technology, Inner Mongolia University of Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Robert Gordon University and Aalborg University
Downloads 32 (1,290,922)
Citation 1

Abstract:

Loading...

Lithium-ion battery, state of charge, state of power, limited memory multiple information least square, H-infinity filtering

28.

Multi-Temperature Capable Enhanced Bidirectional Bidirectional Long Short Term Memory-Multilayer Perceptron Hybrid Model For Lithium-Ion Battery SOC Estimation

Number of pages: 33 Posted: 09 Aug 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 31 (1,304,549)

Abstract:

Loading...

State of charge, lithium-ion battery, BiLSTM, multiple perceptrons, particle swarm optimization algorithm, Genetic algorithm

29.

An Improved Sparrow Search – Early Stopping Convolutional Neural Network Modeling Method for Battery State of Energy Estimation of Energy Storage Systems

Number of pages: 22 Posted: 07 Aug 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology, Robert Gordon University and Aalborg University
Downloads 31 (1,304,549)
Citation 1

Abstract:

Loading...

Power Lithium-ion Battery, State of Energy, Convolutional Neural Network, Sparrow Search Algorithm, Early Stopping Strategy

30.

Improved 2rc-Pngv Modeling and Adaptive Sage-Husa H∞ Filtering for Battery Power State Estimation Based on Multi-Parameter Constraints

Number of pages: 20 Posted: 17 Jul 2024
Shunli Wang and Xinyu Yan
Southwest University of Science and Technology and Inner Mongolia University of Technology
Downloads 31 (1,304,549)

Abstract:

Loading...

lithium-ion battery, Estimation strategy of SOC, Power state estimation strategy, Dynamic particle swarm optimization algorithm, H-infinity filtering, State joint estimation

31.

Improved clustering-multimodal feature decomposition for multi-time scale terminal voltage characterization, edge computing performance evaluation, and retirement prediction of large-capacity batteries in energy storage power stations

Number of pages: 22 Posted: 17 Feb 2026
Southwest University of Science and Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology, Inner Mongolia University of Technology, Inner Mongolia University of Technology and Aalborg University
Downloads 30 (1,372,601)

Abstract:

Loading...

Large-scale energy storage power station, Edge computing, Battery performance evaluation, Cluster analysis, Echelon utilization

32.

High-Precision State of Health Assessment of Aviation Lithium-Ion Ba-Ttery Based on Optimized Multiple Time Scale - Dual Extended Kalm-An Filter Algorithm

Number of pages: 39 Posted: 25 Aug 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Southwest University of Science and Technology
Downloads 29 (1,359,097)

Abstract:

Loading...

Aviation lithium-ion batteries, equivalence modeling, multi-time scales, state of health estimation, adaptive extended Kalman filtering

33.

A Hybrid Neural Network Optimized by an Improved Harris Hawk Algorithm for State of Charge Estimation of Lithium-Ion Batteries Under Wide Temperature Environmental Conditions

Number of pages: 27 Posted: 11 Aug 2025
Inner Mongolia University of Technology, Inner Mongolia University of Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Robert Gordon University and Aalborg University
Downloads 26 (1,385,945)

Abstract:

Loading...

Lithium-ion battery, State of charge estimation, Differential Evolution Algorithm, Harris Hawk Optimization Algorithm, Parameter optimization

34.

Remaining Useful Life Prediction and State of Health Diagnosis of Lithium-Ion Batteries with Multiscale Health Features Based on Optimized Catboost Algorithm

Number of pages: 36 Posted: 22 Feb 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology and Robert Gordon University
Downloads 25 (1,399,036)
Citation 2

Abstract:

Loading...

Lithium-ion battery, Remaining useful life, state of health, CatBoost, IFO-PSO-ACO

Abstract:

Loading...

Lithium-ion battery, energy state, nonlinear variation, Neural network, historical state, harmonic loss

36.

High Precision State of Charge Estimation of Lithium-Ion Batteries Using Improved Multi-Attention Long Short-Term Memory Extended Kalman Filtering Model

Number of pages: 24 Posted: 19 Dec 2024
Inner Mongolia University of Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology and Southwest University of Science and Technology
Downloads 23 (1,436,435)
Citation 5

Abstract:

Loading...

Lithium-ion batteries, state of charge, multi-attention, long short-term memory, extended Kalman filter, temperature compensation

37.

Improved Volumetric Noise-Adaptive H-Infinity Filtering for Accurate Battery State of Power Estimation with Multi-Parameter Constraint Considering Temperature Influence

Number of pages: 22 Posted: 30 Jul 2024
Southwest University of Science and Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology and Robert Gordon University
Downloads 21 (1,436,435)

Abstract:

Loading...

lithium-ion battery, state of charge, state of power, limited memory multiple information least square, H-infinity filtering

38.

An improved Noise Covariance Adaptable X – Unscented Kalman Filtering algorithm for accurate state of charge estimation in lithium-ion batteries adaptive to varying temperature conditions

Number of pages: 21 Posted: 05 May 2026
Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Southwest University of Science and Technology, Robert Gordon University and Aalborg University
Downloads 15 (1,548,648)

Abstract:

Loading...

State-of-charge Estimation, Lithium-ion batteries, Noise Covariance Adaptable X Unscented Kalman Filtering, Battery Management Systems

39.

An Improved Firefly Asymmetric Polarization - Adaptive Extended Kalman Filter Framework Modeling Method for Lithium-ion Battery State Prediction of Power Estimation Adaptive to Extreme Low Temperature Conditions

Number of pages: 30 Posted: 10 Feb 2026
Inner Mongolia University of Technology, Inner Mongolia University of Technology, Southwest University of Science and Technology, Inner Mongolia University of Technology and Robert Gordon University
Downloads 10 (1,548,648)

Abstract:

Loading...

Lithium-ion battery, State of power estimation, Kalman filter, equivalent model, multi-constraint estimation