Publications

 (Corresponding authors asterisked; + Equal contribution)

1. Conduction-mode and keyhole-mode laser welding of 100 μm-thick stainless steel foils using a cw multi-mode fiber laser
   H. Kim, M. Son and H. Ki*
   in preparation (2023).
   
   

2. Vision-to-code framework for autonomous weld seam tracking in laser welding
   K. Nam and H. Ki*
   submitted (2025).
   
   

3. A deep learning model trained on synthetic data for predicting thermal residual stress and melt pool characteristics in laser melting with arbitrary beam profiles
   M. Woo and H. Ki*
   submitted (2025).
   
   

4. AI-based real-time prediction of cross-sectional phase distribution during laser heat treatment via sequential thermal imaging and image-to-image synthesis
   M. Son and H. Ki*
   submitted (2025).
   
   

5. Process monitoring via prediction of laser beam absorptance in partial penetration laser keyhole welding of aluminum alloy
   K. Nam and H. Ki*
   submitted (2025).
   
   

6. Transient electrodynamic simulation of laser beam reflection on inclined surfaces using a GAN-based deep learning model
   M. Son and H. Ki*
   submitted (2023).
   
   

7. Critical heat flux in pool boiling on femtosecond laser-irradiated copper powder-sintered surfaces
   S. Lee, Y. Kim, H. Ki and  J. Lee*
   Thermal Science  and Engineering Progress 60, 103421 (2025.04). link
   
   

8. Prediction of surface reflectance using a deep-learning model trained on synthetic surface images
   J. Yoo and H. Ki*
   Engineering Applications of Artificial Intelligence 133, Part F, 108672 (2024.07). link
   
   

9. Deep learning-based monitoring system for predicting top and bottom bead widths during the laser welding of aluminum alloy
   K. Nam and H. Ki*
   Journal of Manufacturing Processes 120, 616-627 (2024.06.30). link
   
   

10. Deep learning-based prediction of thermal residual stress and melt pool characteristics in laser-irradiated carbon steel
    M. Woo and H. Ki*
    International Communications in Heat and Mass Transfer 155, 107536 (2024.06).  link
    
    

11. Femtosecond laser-treated copper sintering surface to enhance pool boiling heat transfer
    S. Lee, Y. Kim, H. Ki and J. Lee*
    International Communications in Heat and Mass Transfer 152, 107270 (2024.03.01).  link
    
    

12. Deep-learning model for predicting hardness and phase distributions from two cross-sectional temperature distribution images in laser heat treatment of AH36 steel
    M. Son and H. Ki*
    Journal of Materials Research and Technology 27, 718-732 (2023.11-12).
    
    

13. Pool-boiling enhancement on periodic micro/nano ripple-structured surfaces fabricated by femtosecond laser
    S. Lee, Y. Kim, H. Ki and J. Lee*
    International Communications in Heat and Mass Transfer 148, 107072 (2023.11)
    
    

14. One camera-based laser keyhole welding monitoring system using deep learning
    K. Nam and H. KI*
    Journal of Manufacturing Processes 104, 17-27 (2023.10.27).
    
    

15. Deep-learning approach for predicting crystalline phase distribution of femtosecond laser-processed silicon
    H. K. Kim+, M. Woo+ and H. Ki*
    Materials & Design 226, 111639 (2023.02).
    
    

16. Prediction of surface morphology and reflection spectrum of laser-induced periodic surface structures using deep learning
    H. Na+, J. Yoo+ and H. Ki*
    Journal of Manufacturing Processes 84, 1274-1283 (2022.12).
    
    

17. Investigation of microstructure and residual stress development during laser surface melting of AH36 steel using a 3-D fully-coupled numerical model
    H. Yeo, M. Son  and H. Ki*
    International Journal of Heat and Mass Transfer 197, 123366 (2022.11.15).
    
    

18. Enhancement of flow boiling heat transfer by laser-induced periodic surface structures using femtosecond laser
    K. Lim, K. Lee, H. Ki , J. Lee*
    International Journal of Heat and Mass Transfer 196, 123229 (2022.11.01)
    
    

19. Analysis of laser-beam absorptance and keyhole behavior during laser keyhole welding of aluminum alloy using a deep-learning-based monitoring system
    H. Kim+, K. Nam+, Y. Kim, H. Ki*
    Journal of Manufacturing Processes 80, 75-86  (2022.08).
    
    

20. Accurate prediction of the particle image velocimetry flow field and rotor thrust using deep learning
    S. Oh, S.  Lee,  M. Son,  J. Kim*,  H. Ki*
    Journal of Fluid Mechanics 939, A2 (2022.05.25).
    
    

21. Prediction of structural deformation of a deck plate using a GAN-based deep learning method
    S. Oh, H. K. Jin, S. J. Joe and H. Ki*
    Ocean Engineering 239, 109835 (2021.11.01).
    
    

22. Deep-learning-based real-time monitoring of full-penetration laser keyhole welding using the synchronized coaxial observation method
    H. Kim, K. Nam, S. Oh and H. Ki*
    Journal of Manufacturing Processes 68, 1018-1030 (2021.08).
    
    

23. Enhancing coupling efficiency in laser keyhole welding of copper using femtosecond laser surface modification
    K. Lee and H. Ki*
    Optics & Laser Technology 139, 106943 (2021.07).
    
    

24. Deep-learning approach for predicting laser-beam absorptance in full-penetration laser keyhole welding
    S. Oh+, H. Kim+, K. Nam and H. Ki*
    Optics Express 29(13), 20010-20021 (2021.06.21).
    
    

25. Deep-learning approach to the self-piercing riveting of various combinations of steel and aluminum sheets
    H. K. Kim+, S. Oh+, K.-H. Cho, D.-H. Kam* and H. Ki*
    IEEE Access 9, 79316-79325 (2021.05.27).
    
    

26. Unified momentum equation approach for fluid-structure interaction problems involving linear elastic structures
    H. Yeo and H. Ki*
    Journal of Computational Physics 415, 109482 (2020.08.15).
    
    

27. Tunable wetting surfaces with interacting cavities via femtosecond laser patterning and wet etching
    C. Deng and H. Ki*
    Journal of Applied Physics 128(1), 015306 (2020.07.07).
    
    

28. Deep-learning-based predictive architectures for self-piercing riveting process
    S. Oh, H. K. Kim, T.-E. Jeong, D.-H. Kam and H. Ki*
    IEEE Access 8, 116254-116267 (2020.06.23).
    
    

29. Cross-section bead image prediction in laser keyhole welding of AISI 1020 steel using deep learning architectures
    S. Oh and H. Ki*
    IEEE Access 8, 73359-73372 (2020.04.14).
    
    

30. Electrodynamic simulation of laser beam propagation in waterjet-guided laser processing
    C. Deng, H. Yeo and H. Ki*
    Optics Express 28(8), 11128-11143 (2020.04.13).
    
    

31. Femtosecond laser patterning based on the control of surface reflectance
    K. Lee and H. Ki*
    Applied Surface Science 494, 187-195 (2019.11.15).
    
    

32. Fabrication of compound infrared microlens array with ultrashort focal length using femtosecond laser-assisted wet etching and dual-beam pulsed laser deposition
    C. Deng, H. Kim, and H. Ki*
    Optics Express 27(20), 28679-28691 (2019.09.30).
    
    

33. Process optimization for femtosecond laser hole drilling of silicon wafer
    H. Kim and H. Ki*
    Journal of Welding and Joining 37(3), 220-225 (2019.06)
    
    

34. Deep learning model for predicting hardness distribution in laser heat treatment of AISI H13 tool steel
    S. Oh and H. Ki*
    Applied Thermal Engineering 153, 583-595 (2019.05.05).
    
    

35. Investigation of cut quality in fiber laser cutting of CFRP
    S. Oh, I. Lee, Y. Park and H. Ki*
    Optics & Laser Technology 113, 129-140 (2019.05). link
    
    

36. Fabrication of functionally-graded yttria-stabilized zirconia coatings by 355 nm picosecond dual-beam pulsed laser deposition
    C. Deng, H. Kim and H. Ki*
    Composites Part B: Engineering 160, 498-504 (2019.03.01). link
    
    

37. Highly flexible and efficient all‐polymer solar cells with high‐viscosity processing polymer additive toward potential of stretchable devices
    S. Chen, S. Jung, H. J. Cho,  N.‐H. Kim,  S. Jung,  J. Xu,  J. Oh, Y. Cho,  H. Kim,  B. Lee,  Y. An,  C. Zhang,  M. Xiao, H. Ki,  Z.‐G. Zhang, J.‐Y. Kim, Y. Li, H. Park, and C. Yang
    Angewandte Chemie-International Edition 57(40), 13277-13282 (2018.10.01) link
    
    

38. A unified momentum equation approach for computing thermal residual stresses during melting and solidification
    H. Yeo and H. Ki*
    Computer Physics Communications 224, 230-244 (2018.03). link
    
    

39. A study of keyhole behavior and weldability in zero-gap laser welding of zinc-coated steel sheets at subatmospheric pressures
    J. Kim, S. Oh, M. Son and H. Ki*
    Journal of Materials Processing Technology 249, 135-148 (2017.11). link
    
    

40. Fabrication and optimization of transparent conductive films using laser annealing and picosecond laser patterning
    K. Lee and H. Ki*
    Applied Surface Science 420, 886-895 (2017.10.31). link
    
    

41. Prediction of hardness and deformation using a 3-D thermal analysis in laser hardening of AISI H13 tool steel
    S. Oh and H. Ki*
    Applied Thermal Engineering 121, 951-962 (2017.07) link
    
    

42. A unified momentum equation approach for computing flow-induced stresses in structures with arbitrarily-shaped stationary boundaries
    H. Yeo and H. Ki*
    Communications in Computational Physics 22(1), 39-63 (2017.07) link
    
    

43. Effect of beam size in laser welding of ultra-thin stainless steel foils
    J. Kim+, S. Kim+, K. Kim, W. Jung, D. Youn, J. Lee and H. Ki*
    Journal of Materials Processing Technology 233, 125-134 (2016.07) link
    
    

44. Rapid fabrication of transparent conductive films with controllable sheet resistance on glass substrates by laser annealing of diamond-like carbon films
    K. Lee and H. Ki*
    Acta Materialia 111, 315-320 (2016.06) link
    
    

45. Effect of keyhole geometry and dynamics in zero-gap laser welding of zinc-coated steel sheets
    J. Kim, S. Oh and H. Ki*
    Journal of Materials Processing Technology 232, 131-141 (2016.06) link
    
    

46. Electrodynamic simulation of energy absorption in laser keyhole welding of zinc-coated and uncoated steel sheets
    C. Deng, J. Kim, S. Oh and H. Ki*
    Journal of Materials Processing Technology 231, 412-421 (2016.05) link
    
    

47. Pulsed laser deposition of refractive-index-graded broadband antireflection coatings for silicon solar cells
    C. Deng and H. Ki*
    Solar Energy Materials and Solar Cells 147, 37-45 (2016.04) link
    
    

48. A study of keyhole geometry in laser welding of zinc-coated and uncoated steels using a coaxial observation method
    J. Kim, S. Oh and H. Ki*
    Journal of Materials Processing Technology 225, 451-462 (2015.11) link
    
    

49. Water-assisted pulsed Er:YAG laser interaction with silicon
    J. Kim and H. Ki*
    Journal of Applied Physics 118(1), 018105 (2015.07) link
    
    

50. Controlling thermal deformation using a heat sink in laser transformation hardening of steel sheets
    S. Kim, S. So and H. Ki*
    Journal of Materials Processing Technology 216, 455-462 (2015.02) link
    
    

51. Scaling law for penetration depth in laser welding
    J. Kim and H. Ki*
    Journal of Materials Processing Technology 214(12), 2908-2914 (2014.12) link
    
    

52. Laser transformation hardening of carbon steel sheets using a heat sink
    H. Ki*, S. So and S. Kim
    Journal of Materials Processing Technology 214(11), 2693-2705 (2014.11) link
    
    

53. Effect of film gradient profile on adhesion strength, residual stress and effective hardness of functionally graded diamond-like carbon films
    Y. J. Won and H. Ki*
    Applied Surface Science 311, 775-779 (2014.08.30) link
    
    

54. Finite-difference time-domain simulation of laser beam absorption in fully penetrated keyholes
    C. Deng and H. Ki*
    Journal of Applied Physics 114(16), #164901 (2013.10) link
    
    

55. FDTD method for laser absorption in metals for large scale problems
    C. Deng and H. Ki*
    Optics Express 21(21), 25467-25479 (2013.10) link
    
    

56. Effect of specimen thickness on heat treatability in laser transformation hardening
    S. So and H. Ki*
    International Journal of Heat and Mass Transfer 61, pp. 266-276 (2013.06) link
    
    

57. Fabricating functionally graded films with designed gradient profiles using pulsed laser deposition
    Y. J. Won and H. Ki*
    Journal of Applied Physics 113(17), #174910 (2013.05) link
    
    

58. CO2 and Er:YAG laser interaction with grass tissues
    J. Kim and H. Ki*
    Journal of Applied Physics 113(4), #044902 (2013.01) link
    
    

59. 355, 532, and 1064 nm picosecond laser interaction with grass tissues
    J. Kim and H. Ki*
    Journal of Applied Physics 112(11), #114908 (2012.12) link
    
    

60. Surface modification of the patterned Al6061/SUS304 metal plates using the large electron beam
    D.M. Kim, J. Kim, S.S. Park, H.W. Park and H. Ki
    Applied Surface Science 261, 458-463 (2012.11)
    
    

61. Process map for laser heat treatment of carbon steels
    H. Ki* and S. So
    Optics & Laser Technology 44(7), 2106-2114 (2012.10) link
    
    

62. Pulsed laser deposition of functionally gradient diamond-like carbon (DLC) films using a 355 nm picosecond laser
    H. Cho, S. Kim and H. Ki*
    Acta Materialia 60(18), 6237-6246 (2012.10) link
    
    

63. Lattice Boltzmann simulation of laser interaction with weakly ionized helium plasmas
    H. Li and H. Ki*
    Physical Review E 82, #016703 (2010.07) link
    
    

64. Level set method for two phase incompressible flows under magnetic fields
    H. Ki*
    Computer Physics Communications 181(6), 999-1007 (2010.06) link
    
    

65. On vaporization in laser material interaction
    H. Ki*
    Journal of Applied Physics 107, #104908 (2010.05) link
    
    

66. Computation of flow induced stresses in a structure using a hybrid momentum equation approach
    J. Gattu and H. Ki*
    International Journal of Theoretical and Applied Multiscale Mechanics 1(2), 118-133 (2009)
    
    

67. Lattice Boltzmann simulation of weakly-ionized plasmas and fluid flows using physical properties of fluids
    H. Li and H. Ki*
    Journal of Physics A: Mathematical and Theoretical 42, #155501 (2009) link
    
    

68. Simulation of MHD flows using a hybrid lattice-Boltzmann finite-difference method
    H. Li and H. Ki*
    Communications in Computational Physics 4(2), pp. 337-349 (2008)
    
    

69. Lattice Boltzmann method for weakly ionized isothermal plasmas
    H. Li and H. Ki*
    Physical Review E 76, #066707 (2007)
    
    

70. Effect of ionization on the femtosecond laser pulse interaction with silicon
    H. Li and H. Ki*
    Journal of Applied Physics 100, #104907 (2006)
    
    

71. Mass removal modes in the laser ablation of silicon by a Q-switched diode-pumped solid-state laser
    D. Lim, H. Ki* and J. Mazumder
    Journal of Physics D: Applied Physics 39, 2624-2635 (2006)
    
    

72. Numerical simulation of heat transfer and fluid flow in coaxial laser cladding process for direct metal deposition
    H. Qi, J. Mazumder and H. Ki
    Journal of Applied Physics 100, #024903 (2006)
    
    

73. A numerical method for multiphase incompressible thermal flows with solid-liquid and liquid-vapor phase transformations
    H. Ki*, P.S. Mohanty and J. Mazumder
    Numerical Heat Transfer, Part B: Fundamentals 48(2), 125-145 (2005)
    
    

74. Numerical simulation of femtosecond laser interaction with silicon
    H. Ki* and J. Mazumder
    Journal of Laser Applications 17(2), 110-117 (2005)
    
    

75. Modeling of laser keyhole welding – II. Simulation of keyhole evolution, velocity, temperature profile and experimental verification
    H. Ki, P.S. Mohanty and J. Mazumder*
    Metallurgical and Materials Transactions A  33(6), 1831-1842 (2002)
    
    

76. Modeling of laser keyhole welding – I. Mathematical modeling, numerical methodology and role of recoil pressure, multiple reflections, and free surface evolution
    H. Ki, P.S. Mohanty and J. Mazumder*
    Metallurgical and Materials Transactions A 33(6), 1817-1830 (2002)
    
    

77. Multiple reflection and its influence on keyhole evolution
    H. Ki, P.S. Mohanty and J. Mazumder*
    Journal of Laser Applications 14(1), 39-45 (2002)
    
    

78. Modelling of high-density laser-material interaction using fast level set method
    H. Ki, P.S. Mohanty and J. Mazumder*
    Journal of Physics D: Applied Physics 34, 364-372 (2001)
    
    
    

Dr. Ki and his colleagues' work at the University of Michigan was featured in Access Magazine:

Big Kids, Access Magazine (Official Magazine for the National Center for Supercomputing Applications, the University of Illinois), Spring 2002. Also available online at http://access.ncsa.uiuc.edu/Stories/laserkeyhole/