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Letian Wang
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Machine Learning and Deep Learning


ML and DL for heat transfer design

  • Data source:  FEM simulation
  • Model: logistic regression, Convolutional Neural Networks
  • Tool: Python, TensorFlow, Google Compute Engine
  • Results:
    • High classification rate with both models
    • Pattern recognition is best with CNN in terms of the reproducing best
    • clustering effect in the rank plotting
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Video+CNN for additive manufacturing

  • Data source:  video data of nozzle during printing process, defects in the 
  • Model: pre-trained CNN (ResNet-50) , supervised learning, classification  
  • Tool: Python, TensorFlow, Google Compute Engine; 
  • Implemented data augmentation accounting for the random vibration to improve the robustness of the predictor(98%) 
  • Details upon request- for publication concern.

Machine learning for additive manufacturing

  • Data source: real-time temperature data+ laser coordinations
  • Model: SVM, Logistic regression
  • Tool: Python, TensorFlow, Google Compute Engine; 
  • Results: Non-complete report
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ml_for_slm_incomplete.pdf
File Size: 822 kb
File Type: pdf
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Optics, Nanophotonics and Nanofabrication


Transient Reflective Probing

Nano fabrication

Laser sources: CW, nanosecond lasers
Optics: PBS, 1/4 wave, 1/2 wave, notch filter
Oscilloscope, photodetector, color camera
Motion control, NC programming.

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Home-built Microscope

Microscale transmission and reflection probing with different light sources.
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* Nanofabrication for Non-MOS wafer scale photonics metasurfaces and electrical test circuits:
-250nm node layout design (L-edit, Tanner)
-Photolithography(ASML 5500/300)
-RIE(Lam Research, STS)
-Deposition(Ebeam Evaporation, ALD, LPCVD, PECVD)
-Metrology(AFM, Ellipsometry, SEM, Nanospec, FIB)
-Epitaxial growth of Ge on Si (Applied Materials, Centura)
-CD reduction: double deposition and over-etch

*Tool development:
Upgrade the Laser-assisted chemical vapor deposition (LACVD) tool with
-additional high power nanosecond pulsed laser. Carried out damage threshold, beam alignment and focusing tests.
-additional vacuum chamber

*Research and Process Development:
-Laser-assisted atomic layer etching of amorphous silicon film and silicon wafers with Cl2 gases.
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Disclaimer: The schematics and images are originally created by Letian Wang. Most of them are not published.  (c) Letianwang.me 2018

Hardware Development


Micro thermometer with RF electrical measurement and LabView interface

Multi-beam Laser Chemical Processing

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Simulation


Simulator for heat transfer and phase change (home-built for LTL, collaborated with  Jung Bin In)

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Numerical Scheme(​ADE)

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GUI

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Progress Monitor

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Crystallization based on Phase Field Function (CS 294: Software Engineering for Scientific Computing)

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I was in charge of the initiation of the idea, basic algorithm search and test development. Please check my Github and Report.​

cs294-73-final.pdf
File Size: 2513 kb
File Type: pdf
Download File

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Commercial Simulator


Lumerical FDTD 

Mie-scattering

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Pancharatnam-Berry Phase

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Zemax  (EE 218A, Laura Waller)

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COMSOL(thermal, fluid, electrical)

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LTspice

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