Timothy A. Sipkens
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
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2019
Doctor of Philosophy
Mechanical and Mechatronics Engineering
University of Waterloo, Waterloo, Canada
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2015
Masters of Applied Science
Mechanical Engineering
University of Waterloo, Waterloo, Canada
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2012
Bachelor of Applied Science
Mechanical Engineering
University of Waterloo, Waterloo, Canada
Publications & Presentations
- 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
- 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).
- 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).
- 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
- 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
- T. A. Sipkens, J. C. Corbin. Effective density and packing of compacted soot aggregates. Carbon 226, 119197 (2024). 10.1016/j.carbon.2024.119197
- 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
- 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
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- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
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- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
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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.
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An open source set of icons for aerosol instrumentation.
https://github.com/tsipkens/aerosol-icon-project -
A MATLAB codebase to analyze TEM images of soot, which includes new methods associated with this project and a compilation of other pre-existing methods into a single package.
https://github.com/tsipkens/atems -
A Matlab codebase implementing axisymmetric unified background-oriented Schlieren (AUBOS), with supporting functions to analyze Abel and the new ARAP transforms.
https://github.com/tsipkens/aubos -
A set of tools for computing and comparing aerosol properties.
https://github.com/tsipkens/autils -
Perceptually uniform colormaps for MATLAB, compiled from multiple sources.
https://github.com/tsipkens/cmap -
Visualization of mask filtration data from Rogak et al. (Aerosol Sci. Technol., 2021) using HTML/JS, supporting a web app at tsipkens.github.io/fmviz/.
https://github.com/tsipkens/fmviz -
A program to invert aerosol size distributions measurements using a range of methods, including Twomey's iterative method and Tikhonov regularization.
https://github.com/tsipkens/odias -
Code in multiple languages to evaluate the transfer function for particle mass analyzers (including the APM and CPMA), including a web app and Matlab version (cf. github.com/tsipkens/mat-tfer-pma).
https://github.com/tsipkens/tfer-pma