On palimpsests in neural memory: an information theory viewpoint

The finite capacity of neural memory and the reconsolidation phenomenon suggest it is important to be able to update stored information as in a palimpsest, where new information overwrites old information. Moreover, changing information in memory is metabolically costly. In this paper, we suggest that information-theoretic approaches may inform the fundamental limits in constructing such a memory system. In particular, we define malleable coding, that considers not only representation length but also ease of representation update, thereby encouraging some form of recycling to convert an old codeword into a new one. Malleability cost is the difficulty of synchronizing compressed versions, and malleable codes are of particular interest when representing information and modifying the representation are both expensive. We examine the tradeoff between compression efficiency and malleability cost, under a malleability metric defined with respect to a string edit distance. This introduces a metric topology to the compressed domain. We characterize the exact set of achievable rates and malleability as the solution of a subgraph isomorphism problem. This is all done within the optimization approach to biology framework.Accepted manuscrip

Losslees compression of RGB color images

Although much work has been done toward developing lossless algorithms for compressing image data, most techniques reported have been for two-tone or gray-scale images. It is generally accepted that a color image can be easily encoded by using a gray-scale compression technique on each of the three accounts the substantial correlations that are present between color planes. Although several lossy compression schemes that exploit such correlations have been reported in the literature, we are not aware of any such techniques for lossless compression. Because of the difference in goals, the best way of exploiting redundancies for lossy and lossless compression can be, and usually are, very different. We propose and investigate a few lossless compression schemes for RGB color images. Both prediction schemes and error modeling schemes are presented that exploit inter-frame correlations. Implementation results on a test set of images yield significant improvements

Expert Opinion versus Transaction Evidence: Using the Reilly Index to Measure Open Space premiums in the Urban-Rural Fringe

Due to economic and population growth farmland and to a lesser extend other undeveloped areas are under pressure in the urban-rural fringe in British Columbia, Canada. The objectives of this paper are to determine if residential property values near Victoria, BC include open-space premiums for farmland, parks or golf courses, and to determine if using assessed values instead of market prices of the property result in the same findings. We estimate a Seemingly Unrelated Regression (SUR) model with two hedonic pricing equations, one with actual market values as the dependent variable and one with assessed property values, and compare the resulting estimates of shadow prices for open space amenities. Furthermore, we take account of spatial autocorrelation and combine Method of Moment estimates of the spatial parameters in both equations.Hedonic pricing models, spatial dependence, assessed property values, open space.

Data Structures & Algorithm Analysis in C++

This is the textbook for CSIS 215 at Liberty University.https://digitalcommons.liberty.edu/textbooks/1005/thumbnail.jp

Succinct and Self-Indexed Data Structures for the Exploitation and Representation of Moving Objects

Programa Oficial de Doutoramento en Computación . 5009V01[Abstract] This thesis deals with the efficient representation and exploitation of trajectories of objects that move in space without any type of restriction (airplanes, birds, boats, etc.). Currently, this is a very relevant problem due to the proliferation of GPS devices, which makes it possible to collect a large number of trajectories. However, until now there is no efficient way to properly store and exploit them. In this thesis, we propose eight structures that meet two fundamental objectives. First, they are capable of storing space-time data, describing the trajectories, in a reduced space, so that their exploitation takes advantage of the memory hierarchy. Second, those structures allow exploiting the information by object queries, given an object, they retrieve the position or trajectory of that object along that time; or space-time range queries, given a region of space and a time interval, the objects that are within the region at that time are obtained. It should be noted that state-of-the-art solutions are only capable of efficiently answering one of the two types of queries. All of these data structures have a common nexus, they all use two elements: snapshots and logs. Each snapshot works as a spatial index that periodically indexes the absolute position of each object or the Minimum Bounding Rectangle (MBR) of its trajectory. They serve to speed up the spatio-temporal range queries. We have implemented two types of snapshots: based on k2-trees or R-trees. With respect to the log, it represents the trajectory (sequence of movements) of each object. It is the main element of the structures, and facilitates the resolution of object and spatio-temporal range queries. Four strategies have been implemented to represent the log in a compressed form: ScdcCT, GraCT, ContaCT and RCT. With the combination of these two elements we build eight different structures for the representation of trajectories. All of them have been implemented and evaluated experimentally, showing that they reduce the space required by traditional methods by up to two orders of magnitude. Furthermore, they are all competitive in solving object queries as well as spatial-temporal ones.[Resumen] Esta tesis aborda la representación y explotación eficiente de trayectorias de objetos que se mueven en el espacio sin ningún tipo de restricción (aviones, pájaros, barcos, etc.). En la actualidad, este es un problema muy relevante debido a la proliferación de dispositivos GPS, lo que permite coleccionar una gran cantidad de trayectorias. Sin embargo, hasta ahora no existe un modo eficiente para almacenarlas y explotarlas adecuadamente. Esta tesis propone ocho estructuras que cumplen con dos objetivos fundamentales. En primer lugar, son capaces de almacenar en espacio reducido los datos espaciotemporales, que describen las trayectorias, de modo que su explotación saque partido a la jerarquía de memoria. En segundo lugar, las estructuras permiten explotar la información realizando consultas sobre objetos, dado el objeto se calcula su posición o trayectoria durante un intervalo de tiempo; o consultas de rango espacio-temporal, dada una región del espacio y un intervalo de tiempo se obtienen los objetos que estaban dentro de la región en ese tiempo. Hay que destacar que las soluciones del estado del arte solo son capaces de responder eficientemente uno de los dos tipos de consultas. Todas estas estructuras de datos tienen un nexo común, todas ellas usan dos elementos: snapshots y logs. Cada snapshot funciona como un índice espacial que periódicamente indexa la posición absoluta de cada objeto o el Minimum Bounding Rectangle (MBR) de su trayectoria. Sirven para agilizar las consultas de rango espacio-temporal. Hemos implementado dos tipos de snapshot: basadas en k2-trees o en R-trees. Con respecto al log, éste representa la trayectoria (secuencia de movimientos) de cada objeto. Es el principal elemento de nuestras estructuras, y facilita la resolución de consultas de objeto y de rango espacio-temporal. Se han implementado cuatro estrategias para representar el log de forma comprimida: ScdcCT, GraCT, ContaCT y RCT. Con la combinación de estos dos elementos construimos ocho estructuras diferentes para la representación de trayectorias. Todas ellas han sido implementadas y evaluadas experimentalmente, donde reducen hasta dos órdenes de magnitud el espacio que requieren los métodos tradicionales. Además, todas ellas son competitivas resolviendo tanto consultas de objeto como de rango espacio-temporal.[Resumo] Esta tese trata sobre a representación e explotación eficiente de traxectorias de obxectos que se moven no espazo sen ningún tipo de restrición (avións, paxaros, buques, etc.). Na actualidade, este é un problema moi relevante debido á proliferación de dispositivos GPS, o que fai posible a recollida dun gran número de traxectorias. Non obstante, ata o de agora non existe un xeito eficiente de almacenalos e explotalos. Esta tese propón oito estruturas que cumpren dous obxectivos fundamentais. En primeiro lugar, son capaces de almacenar datos espazo-temporais, que describen as traxectorias, nun espazo reducido, de xeito que a súa explotación aproveita a xerarquía da memoria. En segundo lugar, as estruturas permiten explotar a información realizando consultas de obxectos, dado o obxecto calcúlase a súa posición ou traxectoria nun período de tempo; ou consultas de rango espazo-temporal, dada unha rexión de espazo e un intervalo de tempo, obtéñense os obxectos que estaban dentro da rexión nese momento. Cómpre salientar que as solucións do estado do arte só son capaces de responder eficientemente a un dos dous tipos de consultas. Todas estas estruturas de datos teñen unha ligazón común, empregan dous elementos: snapshots e logs. Cada snapshot funciona como un índice espacial que indexa periodicamente a posición absoluta de cada obxecto ou o Minimum Bounding Rectangle (MBR) da súa traxectoria. Serven para acelerar as consultas de rango espazo-temporal. Implementamos dous tipos de snapshot: baseadas en k2-trees ou en R-trees. Con respecto ao log, este representa a traxectoria (secuencia de movementos) de cada obxecto. É o principal elemento das nosas estruturas, e facilita a resolución de consultas sobre obxectos e de rango espacio-temporal. Implementáronse catro estratexias para representar o log nunha forma comprimida: ScdcCT, GraCT, ContaCT e RCT. Coa combinación destes dous elementos construímos oito estruturas diferentes para a representación de traxectorias. Todas elas foron implementadas e avaliadas experimentalmente, onde reducen ata dúas ordes de magnitude o espazo requirido polos métodos tradicionais. Ademais, todas elas son competitivas para resolver tanto consultas de obxectos como espazo-temporais

The development of a weighted directed graph model for dynamic systems and application of Dijkstra’s algorithm to solve optimal control problems.

Master of Science (Chemical Engineering). University of KwaZulu-Natal. Durban, 2017.Optimal control problems are frequently encountered in chemical engineering process control applications as a result of the drive for more regulatory compliant, efficient and economical operation of chemical processes. Despite the significant advancements that have been made in Optimal Control Theory and the development of methods to solve this class of optimization problems, limitations in their applicability to non-linear systems inherent in chemical process unit operations still remains a challenge, particularly in determining a globally optimal solution and solutions to systems that contain state constraints. The objective of this thesis was to develop a method for modelling a chemical process based dynamic system as a graph so that an optimal control problem based on the system can be solved as a shortest path graph search problem by applying Dijkstra’s Algorithm. Dijkstra’s algorithm was selected as it is proven to be a robust and global optimal solution based algorithm for solving the shortest path graph search problem in various applications. In the developed approach, the chemical process dynamic system was modelled as a weighted directed graph and the continuous optimal control problem was reformulated as graph search problem by applying appropriate finite discretization and graph theoretic modelling techniques. The objective functional and constraints of an optimal control problem were successfully incorporated into the developed weighted directed graph model and the graph was optimized to represent the optimal transitions between the states of the dynamic system, resulting in an Optimal State Transition Graph (OST Graph). The optimal control solution for shifting the system from an initial state to every other achievable state for the dynamic system was determined by applying Dijkstra’s Algorithm to the OST Graph. The developed OST Graph-Dijkstra’s Algorithm optimal control solution approach successfully solved optimal control problems for a linear nuclear reactor system, a non-linear jacketed continuous stirred tank reactor system and a non-linear non-adiabatic batch reactor system. The optimal control solutions obtained by the developed approach were compared with solutions obtained by the variational calculus, Iterative Dynamic Programming and the globally optimal value-iteration based Dynamic Programming optimal control solution approaches. Results revealed that the developed OST Graph-Dijkstra’s Algorithm approach provided a 14.74% improvement in the optimality of the optimal control solution compared to the variational calculus solution approach, a 0.39% improvement compared to the Iterative Dynamic Programming approach and the exact same solution as the value–iteration Dynamic Programming approach. The computational runtimes for optimal control solutions determined by the OST Graph-Dijkstra’s Algorithm approach were 1 hr 58 min 33.19 s for the nuclear reactor system, 2 min 25.81s for the jacketed reactor system and 8.91s for the batch reactor system. It was concluded from this work that the proposed method is a promising approach for solving optimal control problems for chemical process-based dynamic systems

New data structures and algorithms for the efficient management of large spatial datasets

[Resumen] En esta tesis estudiamos la representación eficiente de matrices multidimensionales, presentando nuevas estructuras de datos compactas para almacenar y procesar grids en distintos ámbitos de aplicación. Proponemos varias estructuras de datos estáticas y dinámicas para la representación de matrices binarias o de enteros y estudiamos aplicaciones a la representación de datos raster en Sistemas de Información Geográfica, bases de datos RDF, etc. En primer lugar proponemos una colección de estructuras de datos estáticas para la representación de matrices binarias y de enteros: 1) una nueva representación de matrices binarias con grandes grupos de valores uniformes, con aplicaciones a la representación de datos raster binarios; 2) una nueva estructura de datos para representar matrices multidimensionales; 3) una nueva estructura de datos para representar matrices de enteros con soporte para consultas top-k de rango. También proponemos una nueva representación dinámica de matrices binarias, una nueva estructura de datos que proporciona las mismas funcionalidades que nuestras propuestas estáticas pero también soporta cambios en la matriz. Nuestras estructuras de datos pueden utilizarse en distintos dominios. Proponemos variantes específicas y combinaciones de nuestras propuestas para representar grafos temporales, bases de datos RDF, datos raster binarios o generales y datos raster temporales. También proponemos un nuevo algoritmo para consultar conjuntamente un conjuto de datos raster (almacenado usando nuestras propuestas) y un conjunto de datos vectorial almacenado en una estructura de datos clásica, mostrando que nuestra propuesta puede ser más rápida y usar menos espacio que otras alternativas. Nuestras representaciones proporcionan interesantes trade-offs y son competitivas en espacio y tiempos de consulta con representaciones habituales en los diferentes dominios.[Resumo] Nesta tese estudiamos a representación eficiente de matrices multidimensionais, presentando novas estruturas de datos compactas para almacenar e procesar grids en distintos ámbitos de aplicación. Propoñemos varias estruturas de datos estáticas e dinámicas para a representación de matrices binarias ou de enteiros e estudiamos aplicacións á representación de datos raster en Sistemas de Información Xeográfica, bases de datos RDF, etc. En primeiro lugar propoñemos unha colección de estruturas de datos estáticas para a representación de matrices binarias e de enteiros: 1) unha nova representación de matrices binarias con grandes grupos de valores uniformes, con aplicacións á representación de datos raster binarios; 2) unha nova estrutura de datos para representar matrices multidimensionais; 3) unha nova estrutura de datos para representar matrices de enteiros con soporte para consultas top-k. Tamén propoñemos unha nova representación dinámica de matrices binarias, unha nova estrutura de datos que proporciona as mesmas funcionalidades que as nosas propostas estáticas pero tamén soporta cambios na matriz. As nosas estruturas de datos poden utilizarse en distintos dominios. Propoñemos variantes específicas e combinacións das nosas propostas para representar grafos temporais, bases de datos RDF, datos raster binarios ou xerais e datos raster temporais. Tamén propoñemos un novo algoritmo para consultar conxuntamente datos raster (almacenados usando as nosas propostas) con datos vectoriais almacenados nunha estrutura de datos clásica, amosando que a nosa proposta pode ser máis rápida e usar menos espazo que outras alternativas. As nosas representacións proporcionan interesantes trade-offs e son competitivas en espazo e tempos de consulta con representacións habituais nos diferentes dominios.[Abstract] In this thesis we study the efficient representation of multidimensional grids, presenting new compact data structures to store and query grids in different application domains. We propose several static and dynamic data structures for the representation of binary grids and grids of integers, and study applications to the representation of raster data in Geographic Information Systems, RDF databases, etc. We first propose a collection of static data structures for the representation of binary grids and grids of integers: 1) a new representation of bi-dimensional binary grids with large clusters of uniform values, with applications to the representation of binary raster data; 2) a new data structure to represent multidimensional binary grids; 3) a new data structure to represent grids of integers with support for top-k range queries. We also propose a new dynamic representation of binary grids, a new data structure that provides the same functionalities that our static representations of binary grids but also supports changes in the grid. Our data structures can be used in several application domains. We propose specific variants and combinations of our generic proposals to represent temporal graphs, RDF databases, OLAP databases, binary or general raster data, and temporal raster data. We also propose a new algorithm to jointly query a raster dataset (stored using our representations) and a vectorial dataset stored in a classic data structure, showing that our proposal can be faster and require less space than the usual alternatives. Our representations provide interesting trade-offs and are competitive in terms of space and query times with usual representations in the different domains