A general model of competitive and apparent competitive interactions in a spatially-variable envi... more A general model of competitive and apparent competitive interactions in a spatially-variable environment is developed and analyzed to extend findings on coexistence in a temporally-variable environment to the spatial case and to elucidate new principles. In particular, coexistence mechanisms are divided into variation-dependent and variation-independent mechanisms with variation-dependent mechanisms including spatial generalizations of relative nonlinearity and the storage effect. Although directly analogous to the corresponding temporal mechanisms, these spatial mechanisms involve different life history traits which suggest that the spatial storage effect should arise more commonly than the temporal storage effect and spatial relative nonlinearity should arise less commonly than temporal relative nonlinearity. Additional mechanisms occur in the spatial case due to spatial covariance between the finite rate of increase of a local population and its local abundance, which has no clear temporal analogue. A limited analysis of these additional mechanisms shows that they have similar properties to the storage effect and relative nonlinearity and potentially may be considered as enlargements of the earlier mechanisms. The rate of increase of a species perturbed to low density is used to quantify coexistence. A general quadratic approximation, which is exact in some important cases, divides this rate of increase into contributions from the various mechanisms above and admits no other mechanisms, suggesting that opportunities for coexistence in a spatiallyvariable environment are fully characterized by these mechanisms within this general model. Three spatially-implicit models are analyzed as illustrations of the general findings and of techniques using small variance approximations. The contributions to coexistence of the various mechanisms are expressed in terms of simple interpretable formulae. These spatiallyimplicit models include a model of an annual plant community, a spatial multispecies version of the lottery model, and a multispecies model of an insect community competing for spatiallypatchy and ephemeral food. ]
Recent findings on water masses, biogeochemical tracers, deep currents and basin-scale circulatio... more Recent findings on water masses, biogeochemical tracers, deep currents and basin-scale circulation in the East/Japan Sea, and numerical modeling of its circulation are reviewed. Warming continues up to 2007 despite an episode of bottom water formation in the winter of 2000–2001. Water masses have definitely changed since the 1970s and further changes are expected due to the continuation of warming. Accumulation of current data in deep waters of the East/Japan Sea reveals that the circulation in the East/Japan Sea is primarily cyclonic with sub-basin scale cyclonic and anticyclonic cells in the Ulleung Basin (Tsushima Basin). Our understanding of the circulation of intermediate water masses has been deepened through high-resolution numerical studies, and the implementation of data assimilation has had initial success. However, the East/Japan Sea is unique in terms of the fine vertical structures of physical and biogeochemical properties of cold water mass measured at the highest precision and their rapid change with the global warming, so that full understanding of the structures and their change requires in-depth process studies with continuous monitoring programs.
Rate-conversion systems are used in an array of applications, including the oversampled audio and... more Rate-conversion systems are used in an array of applications, including the oversampled audio and video CODECs often found in entertainment and communications systems. It is common practice for many such systems to sample signals at rates which are much faster than the minimum required to represent some bandwidth of interest, and high-quality filters are often implemented at this fast rate. Therefore, their designs tend to be computationallyexpensive. A number of structures have been proposed to address this, including polyphase implementations and folded structures for linear-phase FIR filters. In this thesis, techniques which combine benefits from both classes of structures are discussed, and an efficient class of structures is proposed. The Generalized Transposition Theorem is also reviewed to demonstrate that an efficient downsampling structure also implies an equally efficient, closely-related upsampling structure. Techniques are investigated for designing minimummultiply filters for the class of structures presented, and methods are discussed for designing filters that, for a given set of frequency domain filter specifications, often require fewer multipliers and have smaller maximum error than Parks-McClellan designs.
As the Anglo-Irish Ascendancy's hold on the land of Ireland was being loosened in the late ninete... more As the Anglo-Irish Ascendancy's hold on the land of Ireland was being loosened in the late nineteenth and early twentieth centuries, Somerville and Ross turned to the mode of comic pastoral. William Empson defines the literary mode of pastoral as writing 'about' the common people, but not 'by' or 'for' them. The popular short stories about the experiences of Major Sinclair Yeates, 'the Irish R.M.', depict for a modern readership his encounter with a pre-modern society in rural Ireland which is wild and uncouth compared to the metropolitan world, but at the same time more open, generous, and free from moral strictures. The stories conform to a number of pastoral conventions, including nostalgia for a rural 'golden age' in the recent past, and a thorough-going mixture of high and low elements (e.g., nobility and crudity, kindliness and knavery, etc.).
Optimization of filter banks for specific input statistics has been of interest in the theory and... more Optimization of filter banks for specific input statistics has been of interest in the theory and practice of subband coding. For the case of orthonormal filter banks with infinite order and uniform decimation, the problem has been completely solved in recent years. For the case of biorthogonal filter banks, significant progress has been made recently, although a number of issues still remain to be addressed. In this paper we briefly review the orthonormal case, and then present several new results for the biorthogonal case. All discussions pertain to the infinite order (ideal filter) case. The current status of research as well as some of the unsolved problems are described.
A general model of competitive and apparent competitive interactions in a spatially-variable envi... more A general model of competitive and apparent competitive interactions in a spatially-variable environment is developed and analyzed to extend findings on coexistence in a temporally-variable environment to the spatial case and to elucidate new principles. In particular, coexistence mechanisms are divided into variation-dependent and variation-independent mechanisms with variation-dependent mechanisms including spatial generalizations of relative nonlinearity and the storage effect. Although directly analogous to the corresponding temporal mechanisms, these spatial mechanisms involve different life history traits which suggest that the spatial storage effect should arise more commonly than the temporal storage effect and spatial relative nonlinearity should arise less commonly than temporal relative nonlinearity. Additional mechanisms occur in the spatial case due to spatial covariance between the finite rate of increase of a local population and its local abundance, which has no clear temporal analogue. A limited analysis of these additional mechanisms shows that they have similar properties to the storage effect and relative nonlinearity and potentially may be considered as enlargements of the earlier mechanisms. The rate of increase of a species perturbed to low density is used to quantify coexistence. A general quadratic approximation, which is exact in some important cases, divides this rate of increase into contributions from the various mechanisms above and admits no other mechanisms, suggesting that opportunities for coexistence in a spatiallyvariable environment are fully characterized by these mechanisms within this general model. Three spatially-implicit models are analyzed as illustrations of the general findings and of techniques using small variance approximations. The contributions to coexistence of the various mechanisms are expressed in terms of simple interpretable formulae. These spatiallyimplicit models include a model of an annual plant community, a spatial multispecies version of the lottery model, and a multispecies model of an insect community competing for spatiallypatchy and ephemeral food. ]
Recent findings on water masses, biogeochemical tracers, deep currents and basin-scale circulatio... more Recent findings on water masses, biogeochemical tracers, deep currents and basin-scale circulation in the East/Japan Sea, and numerical modeling of its circulation are reviewed. Warming continues up to 2007 despite an episode of bottom water formation in the winter of 2000–2001. Water masses have definitely changed since the 1970s and further changes are expected due to the continuation of warming. Accumulation of current data in deep waters of the East/Japan Sea reveals that the circulation in the East/Japan Sea is primarily cyclonic with sub-basin scale cyclonic and anticyclonic cells in the Ulleung Basin (Tsushima Basin). Our understanding of the circulation of intermediate water masses has been deepened through high-resolution numerical studies, and the implementation of data assimilation has had initial success. However, the East/Japan Sea is unique in terms of the fine vertical structures of physical and biogeochemical properties of cold water mass measured at the highest precision and their rapid change with the global warming, so that full understanding of the structures and their change requires in-depth process studies with continuous monitoring programs.
Rate-conversion systems are used in an array of applications, including the oversampled audio and... more Rate-conversion systems are used in an array of applications, including the oversampled audio and video CODECs often found in entertainment and communications systems. It is common practice for many such systems to sample signals at rates which are much faster than the minimum required to represent some bandwidth of interest, and high-quality filters are often implemented at this fast rate. Therefore, their designs tend to be computationallyexpensive. A number of structures have been proposed to address this, including polyphase implementations and folded structures for linear-phase FIR filters. In this thesis, techniques which combine benefits from both classes of structures are discussed, and an efficient class of structures is proposed. The Generalized Transposition Theorem is also reviewed to demonstrate that an efficient downsampling structure also implies an equally efficient, closely-related upsampling structure. Techniques are investigated for designing minimummultiply filters for the class of structures presented, and methods are discussed for designing filters that, for a given set of frequency domain filter specifications, often require fewer multipliers and have smaller maximum error than Parks-McClellan designs.
As the Anglo-Irish Ascendancy's hold on the land of Ireland was being loosened in the late ninete... more As the Anglo-Irish Ascendancy's hold on the land of Ireland was being loosened in the late nineteenth and early twentieth centuries, Somerville and Ross turned to the mode of comic pastoral. William Empson defines the literary mode of pastoral as writing 'about' the common people, but not 'by' or 'for' them. The popular short stories about the experiences of Major Sinclair Yeates, 'the Irish R.M.', depict for a modern readership his encounter with a pre-modern society in rural Ireland which is wild and uncouth compared to the metropolitan world, but at the same time more open, generous, and free from moral strictures. The stories conform to a number of pastoral conventions, including nostalgia for a rural 'golden age' in the recent past, and a thorough-going mixture of high and low elements (e.g., nobility and crudity, kindliness and knavery, etc.).
Optimization of filter banks for specific input statistics has been of interest in the theory and... more Optimization of filter banks for specific input statistics has been of interest in the theory and practice of subband coding. For the case of orthonormal filter banks with infinite order and uniform decimation, the problem has been completely solved in recent years. For the case of biorthogonal filter banks, significant progress has been made recently, although a number of issues still remain to be addressed. In this paper we briefly review the orthonormal case, and then present several new results for the biorthogonal case. All discussions pertain to the infinite order (ideal filter) case. The current status of research as well as some of the unsolved problems are described.
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Papers by Ej Noble