L. C. Schwardt
A5079427413- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Advanced Frequency and Time Standards
- Superconducting and THz Device Technology
- Astronomy and Astrophysical Research
- Natural Language Processing Techniques
- Astrophysical Phenomena and Observations
- GNSS positioning and interference
- Speech Recognition and Synthesis
- Ultrasonics and Acoustic Wave Propagation
- Sparse and Compressive Sensing Techniques
- Particle Detector Development and Performance
- Speech and Audio Processing
- Machine Learning and Algorithms
- Voice and Speech Disorders
- Adaptive optics and wavefront sensing
- Phonetics and Phonology Research
- Music and Audio Processing
- Algorithms and Data Compression
- Geophysics and Gravity Measurements
- Stellar, planetary, and galactic studies
- Microwave Imaging and Scattering Analysis
South African Radio Astronomy Observatory
2019-2024
SKA Telescope, South Africa
2012-2018
Stellenbosch University
2000-2002
Abstract We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for newly commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. is a high-gain ( ${\sim}2.8\,\mbox{K Jy}^{-1}$ ) low-system temperature ${\sim}18\,\mbox{K at }20\,\mbox{cm}$ array that currently operates 580–1 670 MHz can produce tied-array beams suitable observations. This paper presents MeerTime Large Survey Project commissioning with PTUSE. Highlights include...
Abstract The inner ∼200 pc region of the Galaxy contains a 4 million M ⊙ supermassive black hole (SMBH), significant quantities molecular gas, and star formation cosmic-ray energy densities that are roughly two orders magnitude higher than corresponding levels in Galactic disk. At distance only 8.2 kpc, presents astronomers with unique opportunity to study diverse range energetic astrophysical phenomena, from stellar objects extreme environments, SMBH star-formation-driven feedback processes...
We present the confusion-limited 1.28 GHz MeerKAT DEEP2 image covering one $\approx 68'$ FWHM primary beam area with $7.6''$ resolution and $0.55 \pm 0.01$ $\mu$Jy/beam rms noise. Its J2000 center position $\alpha=04^h 13^m 26.4^s$, $\delta=-80^\circ 00' 00''$ was selected to minimize artifacts caused by bright sources. introduce new 64-element array describe commissioning observations measure attenuation pattern, estimate telescope pointing errors, pinpoint $(u,v)$ coordinate errors offsets...
The construction of the seven-dish Karoo Array Telescope (KAT-7) array in region Northern Cape South Africa was intended primarily as an engineering prototype for technologies and techniques applicable to MeerKAT telescope. This paper looks at main scientific highlights from this effort, discusses their applicability both other next-generation radio telescopes. In particular, we found that composite dish surface works well, but it becomes complicated fabricate a lacking circular symmetry;...
Compressed sensing (CS) provides the theory behind CLEAN deconvolution step found in aperture synthesis imaging radio astronomy and suggests many new algorithms for it. A few CS algorithms, including greedy methods such as Orthogonal Matching Pursuit (OMP) convex relaxation based on Basis (BP), are evaluated a small dataset produced by KAT-7 array. The outperform standard algorithm this snapshot task.
Higher-order Markov models are more powerful than first-order models, but suffer from an exponential increase in model parameters with order, which leads to data scarcity problems during training. A efficient approach is use mixed-order sequences contexts of different lengths. This study proposes two algorithms for inferringmixed-orderMarkov chains and hiddenMarkovmodels (HMMs), respectively. The basis these the prediction suffix tree (PST), representation a chain. smallest encoded context...
ABSTRACT While observations of the stationary component pulsar radio signals have in many ways formed basis our understanding pulsars, statistical deviations these contain information that has become increasingly relevant. Using high time–frequency resolution data from MeerKAT telescope, we study self-noise autocorrelation function six pulsars. The is used to investigate statistics observed on nanosecond time-scales and for five pulsars it found deviate expected form a Gaussian process....
Voice conversion has recently emerged as an interesting branch of speech processing that deals with the modification a speaker's perceived identity. This technology applications in recognition, entertainment and security industries. paper provides brief introduction to current voice approaches, discusses development PASS system, parametric algorithm based on static speaker characteristics. The system is easy implement, requires no phonetic transcription data, shown be valuable case where...
Radio telescopes are becoming more powerful, with increased sensitivity to both astronomical and interfering sources. Various interference mitigation techniques exist, however they could be harmful the signal of interest, thus it is important develop new techniques. Majority radio sources considered have a Gaussian distribution which fully characterised using second-order power statistics. Higher-order statistics tool that can suppress noise, therefore if energy in higher domains form basis...
This paper reports on the development of an immersion cooling monitoring and prediction system to assist in detection hotspots (i.e., potential points failure due overheating) cooled computing cluster, scheduling maintenance these resources a data centre. Our work focuses case study involving used Science Processor MeerKAT radio astronomy array instrument. relates Square Kilometre Array (SKA) centre situated Karoo, semi-desert region South Africa that experiences high daytime temperatures...
Astronomical sources are characterised using second-order power statistics because they have Gaussian distributions. Spectral Kurtosis is a tool that can suppress noise and therefore be used as an interference mitigation technique. However, care should taken transient such pulsars may contain non-Gaussian components. This paper provides overview of the estimator how one obtains thresholds in order to apply The technique applied Vela pulsar data observed tied-array beamformer mode by MeerKAT...
Polyphase filterbank data of the Vela pulsar is acquired using MeerKAT radio telescope and analysed second-order frequency-frequency polyspectrum. The lack components off non-stationary manifold indicates that process stationary over timescales 0.8 microseconds. Additionally, complex found to be circular thus requires only a small subset possible definitions higher-order moments in its characterisation.