Satellite-based precipitation estimation using watershed segmentation and growing hierarchical self-organizing map

This paper outlines the development of a multi-satellite precipitation estimation methodology that draws on techniques from machine learning and morphology to produce high-resolution, short-duration rainfall estimates in an automated fashion. First, cloud systems are identified from geostationary infrared imagery using morphology based watershed segmentation algorithm. Second, a novel pattern recognition technique, growing hierarchical self-organizing map (GHSOM), is used to classify clouds into a number of clusters with hierarchical architecture. Finally, each cloud cluster is associated with co-registered passive microwave rainfall observations through a cumulative histogram matching approach. The network was initially trained using remotely sensed geostationary infrared satellite imagery and hourly ground-radar data in lieu of a dense constellation of polar-orbiting spacecraft such as the proposed global precipitation measurement (GPM) mission. Ground-radar and gauge rainfall measurements were used to evaluate this technique for both warm (June 2004) and cold seasons (December 2004-February 2005) at various temporal (daily and monthly) and spatial (0.04 and 0.25) scales. Significant improvements of estimation accuracy are found classifying the clouds into hierarchical sub-layers rather than a single layer. Furthermore, 2-year (2003-2004) satellite rainfall estimates generated by the current algorithm were compared with gauge-corrected Stage IV radar rainfall at various time scales over continental United States. This study demonstrates the usefulness of the watershed segmentation and the GHSOM in satellite-based rainfall estimations

General impedance synthesis using simple switching converters

Author name used in this publication: Chi K. TseAuthor name used in this publication: Franki N. K. PoonRefereed conference paper2005-2006 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Synthesis of impedance using switching converters

Author name used in this publication: Chi K. TseAuthor name used in this publication: Franki N.K. PoonAuthor name used in this publication: M.H. PongRefereed conference paper2005-2006 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Synthesis of input-rectifierless ac-dc converters

Author name used in this publication: J. C. P. LiuAuthor name used in this publication: C. K. TseAuthor name used in this publication: M. H. PongRefereed conference paper2000-2001 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Synthesis of input-rectifierless AC/DC converters

This paper discusses the basic construction procedure and topological possibilities of creating ac/dc converters out of simple dc/dc converters. It is shown that two separately controlled dc/dc converters are sufficient for producing a regulated dc output and shaping the input current, from an ac voltage source, without the need for input rectifiers. Some design constraints are discussed, emanating from the limitation of the conversion ratios that can be achieved by particular dc/dc converters. Selected topologies are verified experimentally. This kind of rectifierless converters find applications in airborne power supplies where zero-crossing distortions are significant because of the inevitable phase-lead effect of the input rectifier bridge.published_or_final_versio

Synthesis of input-rectifierless AC-DC converters

This paper discusses the basic construction procedure and topological possibilities of creating ac/dc converters out of simple dc/dc conveners. It is shown that two separately controlled dc/dc conveners are sufficient for producing a regulated dc output and shaping the input current, from an ac voltage source, without the need for input rectifiers. Some design constraints are discussed, emanating from the limitation of the conversion ratios that can be achieved by particular dc/dc converters. Selected topologies are verified experimentally.published_or_final_versio

A PFC topology with low input current distortion suitable for aircraft power supplies

Author name used in this publication: Chi K. TseAuthor name used in this publication: M. H. PongRefereed conference paper2003-2004 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

A PFC voltage regulator with low input current distortion derived from a rectifierless topology

Author name used in this publication: Chi K. Tse2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A PFC topology with low input current distortion suitable for aircraft power supplies

This paper presents an AC-DC converter topology for realization of PFC converters for applications where the mains frequency is high and a low input current harmonics is required, e.g., in aircraft power systems. The proposed topology eliminates crossover distortion due to the presence of input rectifiers and the inevitable input current phase lead. The idea is to stack a DC voltage on top of the AC mains voltage to prevent voltage polarity reversal in the input, eliminating the input bridge rectifier. This eliminates the crossover distortion, which can be significant for supply systems having a high mains frequency. In addition, the proposed PFC converter allows bi-directional energy flow, ensuring all inductors work in continuous conduction mode and hence eliminating the distortion due to the abrupt change of dynamic response when the operating mode changes. Analysis and design of the power and control circuits will be given and discussed. An experimental system will be presented for verification purposes.published_or_final_versio