Preface to the USTC Alumni's Series Preface 1 Introduction 1.1 Brief introduction of experimental observations 1.2 An overview of strain gradient plasticity theory 1.3 Micro-polar theory 2 Micro-scale experiments 2.1 Torsion experiments on copper wires 2.2 Micro-meter thin-beam bending 2.3 Micro-meter particle reinforced metal matrix composite 2.4 Micro and nano-indentation 3 Theories proposed by Fleck and Hutchinson 3.1 Couple stress theory (CS) 3.2 Strain gradient (SG) theory proposed by Fleck and Hutchinson (1997) 3.3 Torsion of thin wires 3.4 Bending of thin beams 3.5 Micro-indentation hardness 3.6 Size effects in particle reinforced metal matrix composites 4 MSG and TNT theories 4.1 A law for strain gradient plasticity 4.2 Deformation theory of MSG 4.3 Bending of thin beams 4.4 Torsion of thin wires 4.5 Micro-indentation hardness 4.6 Size effects in the particle-reinforced metal matrix composit 4.7 Taylor-based non-local theory of plasticity (TNT) 5 C-W strain gradient plasticity theory 5.1 A hardening law for strain gradient plasticity theory 5.2 C-W couple-stress strain gradient plasticity theory 5.3 Verification of C-W couple-stress strain gradient plasticity theory 5.4 C-W strain gradient plasticity theory 5.5 Thin wire torsion and ultra-thin beam bend 5.6 Micro-indentation hardness 5.7 Size effects in particle reinforced metal-matrix composites 6 Strain curl theory 6.1 The continuum theory of dislocation 6.2 Plastic strain curl theory 6.3 Finite element simulation of micro-indentation tests 7 Strain gradient theory based on energy non-local model 7.1 Classical non-local theory of elasticity 7.2 A new framework of non-local theory 7.3 Constitutive equations of strain gradient theory 7.4 Thin wire torsion and ultra-thin beam bend 7.5 Analysis of micro-indentation 8 Cleavage fracture near crack tip 8.1 Steady-state crack growth and work of fracture for solids characterized by strain gradient plasticity 8.2 Fracture in MSG plasticity 8.3 Application of C-W strain gradient plasticity on the cleavage fracture of crack tip 8.4 Prediction of strain-curl theory on plane-strain crack tip field