clustering machine learning 16 Technology: general issues 12 History of engineering & technology 11 Research & information: general 8 classification 8 optimization 8 energy efficiency 7 renewable energy 6 deep learning 5 sustainable development 5 CO2 emissions 4 Internet of Things 4 artificial intelligence 4 cluster analysis 4 data mining 4 energy 4 energy consumption 4 forecasting 4 localization 4 neural networks 4 stress 4 support vector machine 4 Biology, life sciences 3 COVID-19 3 Environmental science, engineering & technology 3 Hamming distance 3 Information technology industries 3 assessment 3 big data 3