Timothy A. Sipkens

Aerosols, Optical Diagnostics, Inverse Analyses, Uncertainty Quantification
tsipkens (at) uwaterloo.ca / timothy.sipkens (at) nrc-cnrc.gc.ca
Ontario, Canada

About

I am an aerosol scientist and researcher interested in optical and physical diagnostics, with a particular focus on data inversion and analysis. My work has included analysis of the products of gas flares, interpreting TEM images with machine learning, modeling of time-resolved laser-induced incandescence (TiRe-LII), particle filtration by face masks and related products, and molecular dynamics simulations of nanoscale heat transfer.

I received my PhD from the University of Waterloo in 2019, with a focus on TiRe-LII as a diagnostic for engineered nanoparticles. From 2018 to 2020, I held a Killam postdoctoral fellowship in the Mechanical Engineering Department at the University of British Columbia. There, I refined aerosol diagnostics, including novel approaches to interpret tandem measurements of aerosol characteristics — e.g., following the use of a centrifugal particle mass analyzer (CPMA) and differential mobility analyzer (DMA) in series — and machine learning techniques to interpret transmission electron microscopy (TEM) images of soot. I also worked on the filtration properties of candidate barrier face covering materials, condensed into a web app here. More recently, I joined the National Research Council Canada, where I continue to work on aerosol measurement.

Education

  • 2019

    Doctor of Philosophy

    Mechanical and Mechatronics Engineering

    University of Waterloo, Waterloo, Canada

  • 2015

    Masters of Applied Science

    Mechanical Engineering

    University of Waterloo, Waterloo, Canada

  • 2012

    Bachelor of Applied Science

    Mechanical Engineering

    University of Waterloo, Waterloo, Canada

Publications & Presentations

    2024

  1. T. A. Sipkens, R. Dastanpour, U. Trivanovic, H. Nikookar, S, N. Rogak. atems: Analysis tools for TEM images of carbonaceous particles. Journal of Open Source Software 9, 6416 (2024). :10.21105/joss.06416
  2. T. E. G. Alvarez‑Arenas, T. A. Sipkens, J. C. Corbin, P. Salso, V. Genovés. Relating the ultrasonic and aerosol filtration properties of filters. Scientific Reports , (2024).
  3. H. Nikookar, T. A. Sipkens, S. N. Rogak. Simulating the effect of post-flame agglomeration on the structure of soot. Aerosol Science and Technology , (2024).
  4. T. A. Sipkens, J. C. Corbin, B. Smith, S. Gagné, P. Lobo, B. T. Brem, M. P. Johnson, G. J. Smallwood. Quantifying the uncertainties in thermal–optical analysis of carbonaceous aircraft engine emissions: an interlaboratory study. Atmospheric Measurement Techniques 17, 4291-4302 (2024). 10.5194/amt-17-4291-2024
  5. J. Scott, T. A. Sipkens, G. Smallwood, R. Mehri, J. C. Corbin, P. Lobo, M. R. Kholghy. Rapid assessment of jet engine-like soot from combustion of conventional and sustainable aviation fuels using flame spray pyrolysis. Aerosol Science and Technology 58, 595-609 (2024). 10.1080/02786826.2024.2316190
  6. T. A. Sipkens, J. C. Corbin. Effective density and packing of compacted soot aggregates. Carbon 226, 119197 (2024). 10.1016/j.carbon.2024.119197
  7. T. Sipkens, J. Corbin, B. Smith, S. Gagné, P. Lobo, B. Brem, M. Johnson, G. Smallwood. Quantifying the uncertainties in thermal-optical analysis of carbonaceous aircraft engine emissions: An interlaboratory study. Atmospheric Measurement Techniques Discussions , 1-17 (2024). 10.5194/amt-2024-1
  8. 2023

  9. T. A. Sipkens, A. Boies, J. C. Corbin, R. K. Chakrabarty, J. Olfert, S. N. Rogak. Overview of methods to characterize the mass, size, and morphology of soot. Journal of Aerosol Science , 106211 (2023). 10.1016/j.jaerosci.2023.106211

    Cover feature

  10. T. A. Sipkens, T. Johnson, R. Nishida, G. J. Smallwood, J. C. Corbin. Technical note: Simplified approaches to estimate the output of particle mass analyzers paired with unipolar chargers. Journal of Aerosol Science 173, 106195 (2023). 10.1016/j.jaerosci.2023.106195
  11. S. E. Laengert, Y. J. Kwon, J. C. Corbin, T. A. Sipkens, P. Morkus, R. J. LaRue, D. R. Latulippe, C. M. Clase, C.-F. de Lannoy. Aerosol charge neutralization and its impact on particle filtration efficiency of common face mask materials. Journal of Aerosol Science 173, 106189 (2023). 10.1016/j.jaerosci.2023.106189
  12. J. P. Molnar, L. Venkatakrishnan, B. E. Schmidt, T. A. Sipkens, S. J. Grauer. Estimating density, velocity, and pressure fields in supersonic flows using physics-informed BOS. Experiments in Fluids 64, 14 (2023). 10.1007/s00348-022-03554-y
  13. T. A. Sipkens, J. C. Corbin, A. Oldershaw, G. J. Smallwood. Particle filtration efficiency measured using sodium chloride and polystyrene latex sphere test methods. Scientific Data 7, 756 (2023). 10.1038/s41597-022-01860-y
  14. T. A. Sipkens, J. C. Corbin, S. J. Grauer, G. J. Smallwood. Tutorial: Guide to error propagation for particle counting measurements. Journal of Aerosol Science 167, 106091 (2023). 10.1016/j.jaerosci.2022.106091
  15. 2022

  16. T. A. Sipkens, J. C. Corbin, T. Koukoulas, A. Oldershaw, T. Lavoie, J. Norooz Oliaee, F. Liu, I. D. Leroux, G. J. Smallwood, P. Lobo, R. G. Green. Comparison of measurement systems for assessing number- and mass-based particle filtration efficiency. Journal of Occupational and Environmental Hygiene 19, 629-645 (2022). 10.1080/15459624.2022.2114596
  17. T. W. Bement, D. Downey, A. Mitros, R. Lau, T. A. Sipkens, J. Songer, H. Alexander, D. Ostrom, H. Nikookar, S. N. Rogak. Filtration and breathability of nonwoven fabrics used in washable masks. Aerosol and Air Quality Research 22, 220044 (2022). 10.4209/aaqr.220044
  18. B. Zhao, T. A. Sipkens, K. J. Daun. Choosing an optimal austenitization submodel using Bayesian model selection. Metallurgical and Materials Transactions A 53, 3022-3033 (2022). 10.1007/s11661-022-06722-1
  19. J. C. Corbin, T. J. Johnson, F. Liu, T. A. Sipkens, M. P. Johnson, P. Lobo, G. J. Smallwood. Size-dependent mass absorption cross-section of soot particles from various sources. Carbon 192, 438-451 (2022). 10.1016/j.carbon.2022.02.037
  20. T. A. Sipkens, J. Menser, T. Dreier, C. Schulz, G. J. Smallwood, K. J. Daun. Laser-induced incandescence for non-soot nanoparticles: recent trends and current challenges. Applied Physics B 128, 1-31 (2022). 10.1007/s00340-022-07769-z
  21. T. A. Sipkens, S. J. Grauer, A. M. Steinberg, S. N. Rogak, P. Kirchen. New transform to project axisymmetric deflection fields along arbitrary rays. Measurement Science and Technology 33, 35201 (2022). 10.1088/1361-6501/ac3f83
  22. A. Naseri, T. A. Sipkens, S. N. Rogak, J. S. Olfert. Optimized instrument configurations for tandem particle mass analyzer and single particle-soot photometer experiments. Journal of Aerosol Science 160, 105897 (2022). 10.1016/j.jaerosci.2021.105897
  23. 2021

  24. J. C. Corbin, G. J. Smallwood, I. Leroux, J. N. Oliaee, F. Liu, T. A. Sipkens, R. G. Green, N. F. Murnaghan, T. Koukoulas, P. Lobo. Systematic experimental comparison of particle filtration efficiency test methods for commercial respirators and face masks. Scientific Reports 11, 21979 (2021). 10.1038/s41598-021-01265-8
  25. T. A. Sipkens, U. Trivanovic, A. Naseri, O. W. Bello, A. Baldelli, M. Kazemimanesh, A. K. Bertram, L. Kostiuk, J. C. Corbin, J. S. Olfert, S. N. Rogak. Using two-dimensional distributions to inform the mixing state of soot and salt particles produced in gas flares. Journal of Aerosol Science 158, 105826 (2021). 10.1016/j.jaerosci.2021.105826
  26. T. A. Sipkens, M. Frei, A. Baldelli, P. Kirchen, F. E. Kruis, S. N. Rogak. Characterizing soot in TEM images using a convolutional neural network. Powder Technology 387, 313-324 (2021). 10.1016/j.powtec.2021.04.026
  27. S. Rogak, T. A. Sipkens, M. Guan, H. Nikookar, D. V. Figueroa, J. Wang. Properties of materials considered for improvised masks. Aerosol Science and Technology 55, 398-413 (2021). 10.1080/02786826.2020.1855321
  28. 2020

  29. T. A. Sipkens, S. N. Rogak. Technical note: Using k-means to identify soot aggregates in transmission electron microscopy images. Journal of Aerosol Science 152, 105699 (2020). 10.1016/j.jaerosci.2020.105699
  30. A. Naseri, T. A. Sipkens, S. N. Rogak, J. S. Olfert. An improved inversion method for determining two-dimensional mass distributions of non-refractory coatings on refractory black carbon. Aerosol Science and Technology 55, 104-118 (2020). 10.1080/02786826.2020.1825615
  31. U. Trivanovic, T. A. Sipkens, M. Kazemimanesh, A. Baldelli, A. M. Jefferson, B. M. Conrad, M. R. Johnson, J. C. Corbin, J. S. Olfert, S. N. Rogak. Morphology and size of soot from gas flares as a function of fuel and water addition. Fuel 279, 118478 (2020). 10.1016/j.fuel.2020.118478
  32. T. A. Sipkens, J. S. Olfert, S. N. Rogak. Inversion methods to determine two-dimensional aerosol mass-mobility distributions II: Existing and novel Bayesian methods. Journal of Aerosol Science 146, 105565 (2020). 10.1016/j.jaerosci.2020.105565
  33. A. Baldelli, U. Trivanovic, T. A. Sipkens, S. N. Rogak. On determining soot maturity: A review of the role of microscopy- and spectroscopy-based techniques. Chemosphere 252, 126532 (2020). 10.1016/j.chemosphere.2020.126532
  34. T. A. Sipkens, J. S. Olfert, S. N. Rogak. Inversion methods to determine two-dimensional aerosol mass-mobility distributions: A critical comparison of established methods. Journal of Aerosol Science 140, 105484 (2020). 10.1016/j.jaerosci.2019.105484

    Cover feature

  35. T. A. Sipkens, J. S. Olfert, S. N. Rogak. New approaches to calculate the transfer function of particle mass analyzers. Aerosol Science and Technology 54, 111-127 (2020). 10.1080/02786826.2019.1680794
  36. 2019

  37. S. Talebi-Moghaddam, T. A. Sipkens, K. J. Daun. Laser-induced incandescence on metal nanoparticles: validity of the Rayleigh approximation. Applied Physics B 125, 214-229 (2019). 10.1007/s00340-019-7325-6
  38. T. A. Sipkens, J. Menser, R. Mansmann, C. Schulz, K. J. Daun. Investigating temporal variation in the apparent volume fraction measured by time-resolved laser-induced incandescence. Applied Physics B 125, 140-159 (2019). 10.1007/s00340-019-7251-7
  39. R. Mansmann, T. A. Sipkens, J. Menser, K. J. Daun, T. Dreier, C. Schulz. Detector calibration and measurement issues in multi-color time-resolved laser-induced incandescence. Applied Physics B 125, 126-146 (2019). 10.1007/s00340-019-7235-7
  40. 2018

  41. T. A. Sipkens, K. J. Daun. Effect of surface interatomic potential on thermal accommodation coefficients derived from molecular dynamics. Journal of Physical Chemistry C 122, 20431-20443 (2018). 10.1021/acs.jpcc.8b06394
  42. T. A. Sipkens, P. J. Hadwin, S. J. Grauer, K. J. Daun. Predicting the heat of vaporization of iron at high temperatures using time-resolved laser-induced incandescence and Bayesian model selection. Journal of Applied Physics 123, 95103 (2018). 10.1063/1.5016341
  43. P. J. Hadwin, T. A. Sipkens, K. A. Thomson, F. Liu, K. J. Daun. A Kalman filter approach for uncertainty quantification in time-resolved laser-induced incandescence. Journal of the Optical Society of America A 35, 386-396 (2018). 10.1364/josaa.35.000386
  44. 2017

  45. T. A. Sipkens, P. J. Hadwin, S. J. Grauer, K. J. Daun. General error model for analysis of laser-induced incandescence signals. Applied Optics 56, 8436-8445 (2017). 10.1364/ao.56.008436
  46. S. J. Grauer, P. J. Hadwin, T. A. Sipkens, K. J. Daun. Measurement-based meshing, basis selection, and prior assignment in chemical species tomography. Optics Express 25, 25135-25148 (2017). 10.1364/oe.25.025135
  47. T. A. Sipkens, K. J. Daun. Using cube models to understand trends in thermal accommodation coefficients at high surface temperatures. International Journal of Heat and Mass Transfer 111, 56-64 (2017). 10.1016/j.ijheatmasstransfer.2017.03.090
  48. P. J. Hadwin, T. A. Sipkens, K. A. Thomson, F. Liu, K. J. Daun. Quantifying uncertainty in auto-compensating laser-induced incandescence parameters due to multiple nuisance parameters. Applied Physics B 123, 114-128 (2017). 10.1007/s00340-017-6693-z
  49. T. A. Sipkens, K. J. Daun. Defining regimes and analytical expressions for fluence curves in pulsed laser heating of aerosolized nanoparticles. Optics Express 25, 5684-5696 (2017). 10.1364/oe.25.005684
  50. T. A. Sipkens, N. R. Singh, K. J. Daun. Time-resolved laser-induced incandescence characterization of metal nanoparticles. Applied Physics B 123, 14-33 (2017). 10.1007/s00340-016-6593-7
  51. 2016

  52. P. J. Hadwin, T. A. Sipkens, K. A. Thomson, F. Liu, K. J. Daun. Quantifying uncertainty in soot volume fraction estimates using Bayesian inference of auto-correlated laser-induced incandescence measurements. Applied Physics B 122, 1-16 (2016). 10.1007/s00340-015-6287-6
  53. 2015

  54. T. A. Sipkens, N. R. Singh, K. J. Daun, N. Bizmark, M. Ioannidis. Examination of the thermal accommodation coefficient used in the sizing of iron nanoparticles by time-resolved laser-induced incandescence. Applied Physics B 119, 409-420 (2015). 10.1007/s00340-015-6022-3
  55. 2014

  56. J. W. Labahn, C. B. Devaud, T. A. Sipkens, K. J. Daun. Inverse analysis and regularization in conditional source-term estimation modelling. Combustion Theory and Modelling 18, 474-499 (2014). 10.1080/13647830.2014.927076
  57. T. A. Sipkens, R. Mansmann, K. J. Daun, N. Petermann, J. T. Titantah, M. Karttunen, H. Wiggers, T. Dreier, C. Schulz. In situ nanoparticle size measurements of gas-borne silicon nanoparticles by time-resolved laser-induced incandescence. Applied Physics B 116, 623-636 (2014). 10.1007/s00340-013-5745-2
  58. 2013

  59. K. J. Daun, T. A. Sipkens, J. T. Titantah, M. Karttunen. Thermal accommodation coefficients for laser-induced incandescence sizing of metal nanoparticles in monatomic gases. Applied Physics B 112, 409-420 (2013). 10.1007/s00340-013-5508-0
  60. T. Sipkens, G. Joshi, K. J. Daun, Y. Murakami. Sizing of molybdenum nanoparticles using time-resolved laser-induced incandescence. Journal of Heat Transfer 135, 52401 (2013). 10.1115/ht2012-58185

Codes

As part of many of my projects, I have code available for use by researchers. Please refer to my GitHub page for more details. Some sample projects are listed below.

More repositories