Browsing by Author "Sharma, Ameeth"

Now showing 1 - 20 of 21
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    Aerosol measurements over South Africa using LIDAR, Satellite and Sun Photometer
    (World Scientific Publishing Company, 2010-05) Sivakumar, V; Tesfaye, M; Alemu, W; Sharma, Ameeth; Bollig, C; Mengistu, G
    In this study, the authors present the climatological picture of aerosols over South Africa using 20 years of Stratosphere Aerosol and Gas Experiment (SAGE-II) satellite, 6–10 years of AErosol RObatic NETwork (AERONET) and ground based mobile LIDAR datasets. The climatological variation of aerosol concentration indicate minimum during winter and maximum over September months. The satellite and ground based measurements are found to be in good agreement with each other. The study affirms the presence of fine and accumulation mode aerosols over industrial areas of South Africa
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    Aerosol measurements over Southern Africa using LIDAR, satellite and sun-photometer
    (2009-08) Sivakumar, V; Tesfaye, M; Alemu, W; Moema, D; Sharma, Ameeth; Bollig, C; Mengistu, G
    This presentation provides aerosol measurement over Southern Africa, using LIDAR, satellite and sun-photometer. Aerosol formation and processes are also given.
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    Atmospheric aerosol load morphological classification and retrieved visibility based on lidar backscatter measurements
    (2010) Tesfaye, M; Sivakumar, V; Mengistu, G; Botai, J; Sharma, Ameeth; Bollig, C; Rautenbach, CJdWH
    In this paper, the tropospheric aerosol load morphological classification and its impact on temporal variation of visibility are investigated using a continuous 23-hour single channel CSIR-NLC mobile LIDAR backscatter measurement. The trajectory of the air mass that arrived at the measurement site was traced back using online HYSPLIT model. The visibility range has been calculated and presented, using average aerosol extinction co-efficient profile and assuming that the atmosphere is homogeneous. The results show that the measurement site is loaded predominantly in the middle and upper troposphere by a transported hazy air-mass.
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    Celebrating the Year of Light….. from medicine to security with Optical Coherence Tomography
    (CSIR, 2015-10) Singh, A; Sharma, Ameeth; Roberts, T; Khutlang, Rethabile; Ramokolo, Lesiba R; Marome, N; Webb, L; Botha, N; Karsten, A; Strauss, Hencharl J
    This poster Celebrating the Year of Light….. from medicine to security with Optical Coherence Tomography was presented at the CSIR’s 5th Conference, 8-9 October 2015.
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    CSIR National Laser Centre develops a high speed OCT system
    (CSIR, 2016-11) Sharma, Ameeth; Singh, Ann; Roberts, Ted; Ramokolo, Lesiba R; Van der Westhuizen, Corrie
    The optical coherence technique (OCT) technique, which was demonstrated by Fercher and Huang in the early 90s, has made significant strides in bio-medical diagnostic applications in the fields of dermatology, dentistry and ophthalmology. Other impact areas and applications include polymer characterisation, surface and thin-film characterisation and biometrics. The National laser Centre has developed a high speed, large area optical coherence tomography (OCT) prototype for fingerprint scanning. The system, which is not limited to this application, can image a large volume (25mm x 25mm x 11mm) and resultant 3-D images (512 x 512 x 2048 pixels) are acquired in less than three seconds. The heart of the system is a swept laser source and a two-axis scanner. Signal acquisition is made possible through a high-speed analogue-to-digital converter capable of speeds greater than 1GS/s. The system has demonstrated the ability to capture live fingerprints making it a viable alternative for high security access control. Furthermore the ability to capture latent fingerprints, from plastic and glass surfaces, was also demonstrated making it applicable to forensics. This paper will present the system design and some of the initial results.
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    CSIR NLC - South Africa - mobile LIDAR - system description
    (2008-05) Sivakumar, V; Sharma, Ameeth; Moema, D; Bollig, C; Van Der Westhuizen, C; Van Wyk, H
    A mobile LIDAR system is being developed at the Council for Scientific and Industrial Research (CSIR) National Laser Centre (NLC), Pretoria (25°5' S; 28°2' E), South Africa. The system is primarily designed for measuring trace gases/pollutants in the troposphere region of the atmosphere. At this moment, the system has been developed for atmospheric backscatter measurements. The complete detailed system description is presented in this paper
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    CSIR NLC mobile lidar observation of cirrus cloud
    (South African Society for Atmospheric Sciences, 2011-09) Sivakumar, V; Sharma, Ameeth; Chiloane, K; Naidoo, S; Lynch, E
    In this paper, the authors present a night-time continuous CSIR-NLC mobile observation of highaltitude cirrus cloud. The LIDAR measurements will also elucidate the aerosol concentration, optical depth, cloud position, thickness and other general properties of the cloud which are important for a better understanding of the earth-radiation budget, global climate change and turbulence.
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    CSIR South Africa mobile LIDAR - First scientific results: comparison with satellite, sun photometer and model simulations
    (Academy of Science of South Africa, 2009-11) Sivakumar, V; Tesfaye, M; Alemu, W; Moema, D; Sharma, Ameeth; Bollig, C; Mengistu, G
    The authors present the first scientific results from the Council for Scientific and Industrial Research-National Laser Centre (CSIR-NLC) mobile LIght Detection And Ranging (LIDAR) and its validation and comparison with other ground-based and space-borne measurements. The LIDAR results are compared with aerosol extinction measurements from the Stratosphere Aerosol Gas Experiment (SAGE) II, optical depth derived from sun photometers employed under the AErosol RObotic NETwork (AERONET) and backscatter coefficients simulated from weather balloon humidity measurements.
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    CSIR-NLC mobile LIDAR for atmosphere remote sensing
    (IEEE, 2009-07) Sivakumar, V; Tesfaye, M; Botai, J; Moema, D; Sharma, Ameeth; Bollig, C; Hannes Rautenbach, CJ
    A mobile LIDAR (LIght Detection And Ranging) system is being developed and employed for atmosphere remote sensing at the Council for Scientific and Industrial Research (CSIR) National Laser Centre (NLC), Pretoria (25.45 S;28.16 E), South Africa. In this paper, researchers describe the results obtained using the CSIR-NLC mobile LIDAR in a 23 hour field campaign at the University of Pretoria.
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    CSIR-NLC mobile LIDAR: first scientific results
    (IEEE International Geoscience and Remote Sensing Symposium, 2009-07) Sivakumar, V; Tesfaye, M; Moema, D; Sharma, Ameeth; Bollig, C
    In this paper, researchers present the obtained first scientific results from CSIR-NLC mobile LIDAR (LIght Detection And Ranging) and its validation/comparison with other ground and space-borne measurements. The LIDAR results are compared using aerosol measurements from the Stratosphere Aerosol Gas Experiment (SAGE) and Optical depth derived from sun-photometer employed under AErosol RObotic NETwork (AERONET).
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    Development of 2-channel (532 nm and 355 nm) mobile LIDAR for mapping particulate matter in the atmosphere
    (2010-09) Sivakumar, V; Bollig, C; Sharma, Ameeth; Tesfaye, M
    In this paper, the authors describe the developmentof 2-Channel (532 nm and 355 nm) mobile LIDAR system for studying atmospheric particulate matter. The system is currently tested in house at the Council for Scientific and Industrial Research - National Laser Centre (CSIR - NLC), Pretoria, South Africa.
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    Dialogue design for the openphone system
    (CSIR, 2008-11) Ndwe, TJ; Sharma, Ameeth; Kgampe, M; Kuun, C
    Skilful dialogue design in an interactive voice response system has facilitated the effective use of a telephone-based health information syatem ny caregivers to HIV/AIDS-infected childern in Botswana. The intended users, caregivers, can access information over telephone line in their local language. This uniqueness necessitates the design of a system to meet specific concerns and decisions, which will ensure its usefulness and usability to its intended users. This document describes both context and content design of the dialogue system.
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    Evaluating the potential of automated telephony systems in rural communities: Field assessment for project Lwazi of HLT Meraka
    (CSIR, 2008-11) Gumede, T; Plauche, M; Sharma, Ameeth
    The authors describe sociological fieldwork conducted in the autumn of 2008 in two rural communities of South Africa. Tshidilamalomo, in North West Province, and Kgautswane, in Limpopo Province. The goal of the fieldwork was to evaluate the potential role automated telephony services in the improving access to important government information and services. Our interviews, focus groups and surveys revealed that an automated telephony service could be greatly support current government efforts to effectively connect citizens to available services, provided such services are toll free, in local language, and with content relevant to the particular rural community
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    A high speed OCT system developed at the CSIR National Laser Centre
    (South African Institute of Physics (SAIP), 2016-07) Sharma, Ameeth
    Light based techniques continue to gain momentum in different spheres of diagnostic and therapeutic applications as a result of their non-invasive, noncontact properties. One such technique is Optical Coherence tomography (OCT). Since it was first reported by Huang in 1991[1], OCT has made significant strides in different fields from dermatology and ophthalmology to polymer characterisation and bio-metrics[2-4]. In South Africa, the technique is still emerging although it is being used for eye examinations by ophthalmologists. The type of OCT system employed can be a simple, cost effective solution or a complex, highly specific and fast system depending on the application. As part of a larger project, the CSIR National Laser Centre has designed and built a high speed OCT system that can image a large surface area (25 by 25 mm) to a depth of 11 mm (sample dependant). Resultant 3-D images (512 x 512 x 2048 pixels) are acquired in less than 3 seconds. The performance of the system compares adequately with many commercially available systems which usually image smaller areas [5-6]. The heart of the system is a 200 kHz swept laser source and two axis galvonometer based scanner. Signal acquisition is made possible through a high speed analogue-to-digital converter capable of speeds greater than 1GS/s. This paper will give an overview of the system and elaborate on the design of the data acquisition system and the initial results that have been obtained.
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    A high speed OCT system developed at the CSIR National Laser Centre (paper)
    (The South African Institute of Physics, 2016-07) Sharma, Ameeth; Singh, Ann; Roberts, Ted; Ramokolo, Lesiba R; Strauss, Hencharl J
    Light-based techniques continue to gain momentum in different spheres of diagnostic and therapeutic applications due to their non-invasive, non-contact properties. One such technique is Optical Coherence tomography (OCT). Since first being reported by Huang in 1991, OCT has made significant strides in different fields such as dermatology, ophthalmology, polymer characterisation and biometrics. The type of OCT system employed can be a simple, cost effective solution or a complex, highly specific and fast system depending on the application. As part of a larger project, we have designed and built a high speed OCT system that can image a large surface area (25 by 25 mm) to a depth of 11 mm (sample dependant). Resultant 3-D images (512 x 512 x 2048 pixels) are acquired in less than 3 seconds. The heart of the system is a 200 kHz swept laser source and two-axis galvanometer based scanner. Signal acquisition is made possible through a high-speed analogue-to-digital converter capable of speeds greater than 1GS/s. This paper will give an overview of the system design and the specifications that have been obtained.
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    LIDAR for atmosphere research over Africa
    (2008-11) Sivakumar, V; Moema, D; Bollig, C; Sharma, Ameeth; Mbatha, N; Malinga, S; Mengistu, G; Bencherif, H; Keckhut, P
    This paper describes the LIDAR for atmosphere research over Africa and current initiatives being undertaken in South Africa. A mobile LIDAR system is being developed at the Council for Scientific and Industrial Research (CSIR) National Laser Centre (NLC), Pretoria (25°5′ S; 28°2′ E), South Africa, for remote sensing the atmosphere. The initial results conclude that the system is capable of providing aerosol/cloud backscatter measurements for the height region from ground to 40 km with a 10 m vertical height resolution
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    Retrieval of atmospheric boundary layer height by CSIR NLC mobile LIDAR, Pretoria (25.5° S; 28.2° E), South Africa
    (IEEE, 2011-07) Sivakumar, V; Sharma, Ameeth; Bollig, C
    In this paper, the authors present the preliminary methods for detection of the boundary layer based on backscattered signals from a mobile LIDAR (LIght Detection And Ranging) developed at Council for Scientific and Industrial Research (CSIR) National Laser Centre (NLC), Pretoria (25.5º S; 28.2º E), South Africa. They've concentrated on two different methods, such as (a) statistical and (b) slope. The preliminary study concludes that the statistical method provides a reasonable temporal evolution of the boundary layer height in comparison with the slope method.
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    Retrieval of relative humidity from CSIR-NLC mobile LIDAR backscatter measurements
    (2009-09) Tesfaye, M; Sivakumar, V; Botai, J; Moema, D; Sharma, Ameeth; Bollig, C; Hannes Rautenbach, CJ deW; Mengistu, G
    The CSIR-NLC mobile LIDAR has been operated at the University of Pretoria during October 2008 for a better understanding of the atmosphere's boundary layer evolution and aerosol (solid particles suspended in the air) concentrations. The experimental data was collected over 23 hours. The above data sets were used to determine the retrieved relative humidity and compared with Irene (near to Pretoria) weather balloon humidity measurements. The results of the comparative study are presented in this paper.
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    A review of the mobile LIDAR system developed at the CSIR and a proposed improvement of the system
    (2012-07) Shikwambana, L; Sivakumar, V; Sharma, Ameeth
    LIDAR is an acronym for light detection and ranging, it is analogous to radar (radio detection and ranging), except that it is based on discrete light pulses and measured travel times. We report on the mobile LIDAR system developed at the CSIR-National Laser Centre. We show some measurements that have been done with this system. We also show the alterations planned to improve the system.
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    Rugged and compact mid-infrared solid-state laser for avionics applications
    (2009-11) Esser, MJD; Preussler, D; Sharma, Ameeth; Jacobs, Cobus; Bollig, C
    In order to demonstrate the feasibility of a helicopter-based application using advanced laser technology, the authors have developed a rugged and compact mid-infrared solid-state laser. The requirement for the laser was to simultaneously emit at 2.3 μm and 4.0 μm wavelength at a multi-kilohertz repetition rate, the output of which can be amplitude modulated. The mid-infrared wavelength output was required in order to propagate the laser beam over several kilometres within an atmospheric transmission window.