fuzzy logic History of engineering & technology 9 machine learning 9 Technology: general issues 8 deep learning 7 Research & information: general 5 artificial intelligence 5 calibration 5 multi-objective optimization 5 IoT 4 cadence 4 classification 4 convolutional neural network 4 fast Fourier transform (FFT) 4 feature extraction 4 human activity recognition 4 inertial sensors 4 kinematics 4 kinetics 4 neural networks 4 physical activity 4 semi-Markov model 4 sensor fusion 4 smart grid 4 smartphones 4 wearable sensors 4 wearables 4 3-axis force sensor 3 ANOVA analysis 3 Achilles tendon 3