THOMAS Y. WU

Dr. THOMAS Y. WU

Agency for Science, Technology and Research, Singapore, Central Singapore, Singapore
orcid

Research Focus & Metrics

Academic Career Length

28Years (1999-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 September 2021 in Journal of Aerosol Science
Verified
Journal Article
Open access
KVKonstantina Vasilatou
Konstantina Vasilatou
CWChristian Wälchli
Christian Wälchli
SKStig Koust
Stig Koust
SHStefan Horender
Stefan Horender
KIKenjiro Iida
Kenjiro Iida
KAKevin Auderset
Kevin Auderset

1 August 2003 in IEE Proceedings - Radar, Sonar and Navigation
Verified
Journal Article
Closed access
ALA.D. Lanterman
A.D. Lanterman
DMD.C. Munson
D.C. Munson
THOMAS Y. WUTHOMAS Y. WU
THOMAS Y. WU
Low-frequency radar systems provide some attractive advantages in a few niche applications, such as foliage penetration and covert operation. In low-frequency imaging systems, data must be collected over a wide range of angles to obtain cross-range resolution comparable to that obtainable from a competing small-angle high-frequency system. The reflectivity of a target varies with aspect angle; although this variation is usually ignored by traditional radar imaging algorithms, it sometimes cannot be neglected in wide-angle scenarios. To account for aspect dependence of reflectivity, time–frequency transforms have been invoked to generate a series of images corresponding to different look angles; these images may be considered individually or synthesised into a single image. A simple theoretical analysis with a point scatter illustrates why the angular dependence needs explicit consideration. The potential of time–frequency methods is illustrated via simulations.

19 August 2022 in Measurement
Verified
Journal Article
Open access
THOMAS Y. WUTHOMAS Y. WU
THOMAS Y. WU
SHStefan Horender
Stefan Horender
GTGeorgi Tancev
Georgi Tancev
KVKonstantina Vasilatou
Konstantina Vasilatou
We have evaluated the PM10 and PM2.5 measurement using a Grimm 11-D optical particle size spectrometer (OPSS) with ambient-like aerosols generated in a laboratory. The ambient-like model aerosols include fresh soot, aged soot, ammonium sulfate, ammonium nitrate and Arizona Road Dust (ARD) particles. The mass concentration (MC) of test aerosols has been computed from the particle counts, equivalent particle volume and particle effective density using a proposed method. The expanded measurement uncertainties for the computed MC are estimated to be 27–36%, with detailed uncertainty analysis. The deviation of the computed MC from the reference gravimetric values is below 20% for MC levels from 29 to 1584 µg/m3. The computed MC agree with the reference MC within their measurement uncertainties. The underestimation and overestimation of the computed MC at various MC levels have been explained based on OPSS sizing errors related to the light-scattering and absorption property of the model aerosols. The proposed MC computation method is useful to evaluate the accuracy of OPSS in PM10 and PM2.5 measurement with the lab-generated model aerosols. This method can also be used to compare the performance of various OPSS-based PM monitors via inter-laboratory comparisons.

1 May 2016 in Measurement
Verified
Journal Article
Closed access
Patrice SalzensteinPatrice Salzenstein
Patrice Salzenstein
THOMAS Y. WUTHOMAS Y. WU
THOMAS Y. WU

15 July 2023 in Micromachines
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Journal Article
Open access
PDF file
Patrice SalzensteinPatrice Salzenstein
Patrice Salzenstein
THOMAS Y. WUTHOMAS Y. WU
THOMAS Y. WU
The expanded uncertainty of the measured Brillouin scattering shift frequencies is essential in assessing the measurements of parameters of various materials. We describe the general operation principles of a Brillouin light scattering (BLS) spectrometer with a high-power laser and a scanning tandem Fabry–Pérot interferometer (TFPI) for material characterization. Various uncertainty components have been analyzed for the BLS spectrometer following the Guide to the Expression of Uncertainty in Measurement (GUM). The expanded relative uncertainty in the measured Brillouin frequency shift of 15.70 GHz for polymethyl methacrylate (PMMA) was estimated to be 0.26%. The calculated Brillouin frequency shift (based on material properties of PMMA) was determined to be 15.44 GHz with expanded relative uncertainty of 2.13%. It was shown that the measured and calculated Brillouin frequency shifts for PMMA agree within their expanded uncertainties. The TFPI-based BLS spectrometer can be used to measure the longitudinal modulus of materials with an expanded uncertainty of 1.9%, which is smaller than that of the ultrasonic velocity-based method (estimated to be 2.9%).

1 June 2021 in Measurement
Verified
Journal Article
Closed access
THOMAS Y. WUTHOMAS Y. WU
THOMAS Y. WU
AKAsaad Kenbar
Asaad Kenbar
APAart Pruysen
Aart Pruysen