1,721,018 research outputs found
IEEE GRSS Malaysia Chapter: Report of Activities for 2018-2020 [Chapters]
No full textThe IEEE Geoscience and Remote Sensing Society
(GRSS) Malaysia Chapter was formed in November
2012 by Tan Sri Prof. Ir. Dr. Chuah Hean Teik, former
president of Universiti Tunku Abdul Rahman (UTAR),
with the aim of providing a platform for sharing expertise and experiences in all aspects of geoscience and remote sensing among professionals from both academia
and industry. Prof. Chuah served as founding chair of
the Chapter from 2012 to 2015, followed by Prof. Ir. Dr.
Koo Voon Chet, Multimedia University (2015–2017);
Prof. Dr. Biswajeet Pradhan, Universiti Putra Malaysia
(2017–2018); and Prof. Ir. Dr. Ewe Hong Tat, president
UTAR (2018–present). The weblink with details about
the Chapter are available at http://grss.ieeemy.org
A Microwave Scattering Model For An Electrically Dense Discrete Random Medium
No full textThis thesis contains a theoretical study of the microwave scattering problems in electrically dense discrete random media and the development of the microwave scattering models with applications to these dense media. A medium is considered electrically dense when the average distance between the scatterers is smaller than the wavelength. In this case, the conventional assumption of independent scattering from the scatterers is no longer valid and the coherence effect from the scatterers should be taken into account. This effect can be included by incorporating the array phase correction factor to the scattering matrix of the scatterers. The array phase correction factor is developed based on the antenna array concept where the overall phase contributions from the correlated scatterers are considered. In this study, the array phase correction factor for spherical scatterers developed by Chuah et.al. ( 1996) is generalized to non -spherical scatteres with either prescribed or random orientation. Theoretical analysis of the array factor for various frequencies, valume fractions and scattering angles is also carried out. In addition to the coherence effect, the near field interaction between the scatterers should also be incorporated in the scattering theory for a dense medium. For spherical scatterers, this near field interaction effect is considered through the amplitude correction where the range dependent terms in the exact expression of the scattered field of Mie scatterers are included. For disks, needles and cylinders, since the overall scattered field of a scatterer is approximated by integrating the scattered fields from each volume element of the scatterer, the near field interaction effect is considered by including not only the near field amplitude term of the scattered fields ( as the amplitude correction ) but also the higher order terms in the phase of the scattered fields ( as the Fresnel phase correction ). For the application of the theoretical model in a dense medium embedded with spherical scatterers such as now, a scattering problem from a single layer of Mie scatterers bounded both on top and bottom by rough interfaces characterized by the IEM model is considered. Theoretical analysis of the model with the amplitude and the array phase corrections is carried out with comparison to the predictions of the dense medium matrix doubling model. In addition, the model predictions are also compared with laboratory and snow field measurement data. Encouraging results are obtained where good agreement with the snow measurement data for co-polarization returns is observed. For cross-polarization returns, more high order terms are found to be necessary for better model predictions. For the study of scattering mechanisms in a vegetation medium, the single layer model is extended to a multilayer model. The leaves, branches and trunks are modelled by simple geometrical shapes such as disks, needles and cylinders. The IEM model is again used to characterize the ground surface. Theoretical studies of the effects of the array phase, the amplitude and the Fresnel phase corrections on the phase matrices of disks, needles and cylinders are presented and good agreement is obtained between the theoretical results and the backscattering cross section measurement of rods, disks, birch stick and aspen leaf. The phase matrices are then applied in the backscatter model and theoretical analysis of the backscattering returns from both the single layer and the multilayer models is carried out. Three types of forests are chosen for the theoretical study of the multilayer model: temperate coniferous forest, tropical deciduous forest and tropical evergreen forest. Various dominat scattering contributions from the vegetation are identified and siscussed. Good agreement is obtained between model predictions and multi-frequency, multi-angle and multi-polarization measurement data for Japanese Cypress, soybean and wheat canopies, boreal forest, walnut orchard and Sugi coniferous trees. In conclusion, it is generally found that the arry phase correction is necessary for an electrically dense medium. In addition, near field interactions such as the amplitude correction and the Fresnel phase correction are also vital in the dense medium models. Good agreement of the model predictions with the available measurement results validates the applicability of the models in this study
Radiative transfer theory for active and passive remote sensing of sea ice
Get PDFThesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (p. 147-153).by Hong Tat Ewe.M.S
Remote sensing backscattering model for sea ice: Theoretical modelling and analysis
Get PDFRemote sensing has been used in Antarctic studies as an earth observation technique to study the polar region. A remote sensing forward model is an important tool in polar research to study and understand scattering mechanisms and sensitivity of physical parameters of snow and sea ice. In this paper, a reliable theoretical model to study sea ice is developed. The theoretical model in a prior work was improved by including multiple-surface scattering, based on an existing integral equation model and additional second-order surface-volume scattering. This model is applied to a desalinated ice layer above thick saline ice and analyzed using different frequencies, bottom surface roughness and sea-ice layer thickness. Improvement in calculation of the backscattering coefficient of the sea-ice layer is investigated for both co-polarized and cross-polarized returns. The effect on each scattering mechanism is also investigated, to understand in more detail the effect of surface multiple scattering and second-order surface-volume scattering. Comparisons are also made with field measurement results, to validate the theoretical model. Results show improvement in the total backscattering coefficient for cross-polarized return in the studied range, suggesting that multiple-surface scattering and surface-volume scattering up to second order are important scattering mechanisms in the sea-ice layer and should not be ignored in polar research
Model development and analysis of multiple surface scattering and surface-volume scattering in sea ice layer
No full textA model for secure knowledge sharing
No full textImprovements made in digital data processing resulted in the ability to store knowledge objects in sharing systems in the form of documents, images, audio and even video streams. However, with the increasing reliance on online knowledge sharing technologies, there is also an increasing danger that knowledge objects stored in digital forms are subjected to concerted malicious and possible criminal attacks. Digital knowledge objects can become easy prey to tampering and modifications which may defeat the original intent for knowledge sharing as well as causing loss of confidence among users. The preservation of the integrity of digital knowledge objects becomes increasingly important now than ever and the need has come for technologies to safeguard the authenticity and integrity of such objects. This paper proposes a model to incorporate automated detection and recovery mechanisms for tampered knowledge objects to make sure that knowledge-processing resources continue to perform correct processing operations at all times
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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