Reduced-Dimension Linear Transform Coding of Correlated Signals in Networks

A model, called the linear transform network (LTN), is proposed to analyze the compression and estimation of correlated signals transmitted over directed acyclic graphs (DAGs). An LTN is a DAG network with multiple source and receiver nodes. Source nodes transmit subspace projections of random correlated signals by applying reduced-dimension linear transforms. The subspace projections are linearly processed by multiple relays and routed to intended receivers. Each receiver applies a linear estimator to approximate a subset of the sources with minimum mean squared error (MSE) distortion. The model is extended to include noisy networks with power constraints on transmitters. A key task is to compute all local compression matrices and linear estimators in the network to minimize end-to-end distortion. The non-convex problem is solved iteratively within an optimization framework using constrained quadratic programs (QPs). The proposed algorithm recovers as special cases the regular and distributed Karhunen-Loeve transforms (KLTs). Cut-set lower bounds on the distortion region of multi-source, multi-receiver networks are given for linear coding based on convex relaxations. Cut-set lower bounds are also given for any coding strategy based on information theory. The distortion region and compression-estimation tradeoffs are illustrated for different communication demands (e.g. multiple unicast), and graph structures.Comment: 33 pages, 7 figures, To appear in IEEE Transactions on Signal Processin

Computation in Multicast Networks: Function Alignment and Converse Theorems

The classical problem in network coding theory considers communication over multicast networks. Multiple transmitters send independent messages to multiple receivers which decode the same set of messages. In this work, computation over multicast networks is considered: each receiver decodes an identical function of the original messages. For a countably infinite class of two-transmitter two-receiver single-hop linear deterministic networks, the computing capacity is characterized for a linear function (modulo-2 sum) of Bernoulli sources. Inspired by the geometric concept of interference alignment in networks, a new achievable coding scheme called function alignment is introduced. A new converse theorem is established that is tighter than cut-set based and genie-aided bounds. Computation (vs. communication) over multicast networks requires additional analysis to account for multiple receivers sharing a network's computational resources. We also develop a network decomposition theorem which identifies elementary parallel subnetworks that can constitute an original network without loss of optimality. The decomposition theorem provides a conceptually-simpler algebraic proof of achievability that generalizes to $L$-transmitter $L$-receiver networks.Comment: to appear in the IEEE Transactions on Information Theor

Fabrication of lightweight Si/SiC LIDAR mirrors

A new, chemical vapor deposition (CVD) process was developed for fabricating lightweight, polycrystalline silicon/silicon-carbide (Si/SiC) mirrors. The process involves three CVD steps: (1) to produce the mirror faceplate; (2) to form the lightweight backstructure, which is deposited integral to the faceplate; and (3) to deposit a layer of optical-grade material, e.g., Si, onto the front surface of the faceplate. The mirror figure and finish are fabricated into the faceplate

Using remote sensing as a support to the implementation of the European Marine Strategy Framework Directive in SW Portugal

The exclusive economic zones (EEZ) of coastal countries are coming under increasing pressure from various economic sectors such as fishing, aquaculture, shipping and energy production. In Europe, there is a policy to expand the maritime economic sector without damaging the environment by ensuring that these activities comply with legally binding Directives, such as the Marine Strategy Framework Directive (MSFD). However, monitoring an extensive maritime area is a logistical and economic challenge. Remote sensing is considered one of the most cost effective, methods for providing the spatial and temporal environmental data that will be necessary for the effective implementation of the MSFD. However, there is still a concern about the uncertainties associated with remote sensed products. This study has tested how a specific satellite product can contribute to the monitoring of a MSFD Descriptor for "good environmental status" (GES). The results show that the quality of the remote sensing product Algal Pigment Index 1 (API 1) from the MEdium Resolution Imaging Spectrometer (MERIS) sensor of the European Space Agency for ocean colour products can be effectively validated with in situ data from three stations off the SW Iberian Peninsula. The validation results show good agreement between the MERIS API 1 and the in situ data for the two more offshore stations, with a higher coefficient of determination (R-2) of 0.79, and with lower uncertainties for the average relative percentage difference (RPD) of 24.6% and 27.9% and a root mean square error (RMSE) of 0.40 and 0.38 for Stations B and C, respectively. Near to the coast, Station A has the lowest R-2 of 0.63 and the highest uncertainties with an RPD of 112.9% and a RMSE of 1.00. It is also the station most affected by adjacency effects from the land: when the Improved Contrast between Ocean and Land processor (ICOL) is applied the R-2 increases to 0.77 and there is a 30% reduction in the uncertainties estimated by RPD. The MERIS API 1 product decreases from inshore to offshore, with higher values occurring mainly between early spring and the end of the summer, and with lower values during winter. By using the satellite images for API 1, it is possible to detect and track the development of algal blooms in coastal and marine waters, demonstrating the usefulness of remote sensing for supporting the implementation of the MSFD with respect to Descriptor 5: Eutrophication. It is probable that remote sensing will also prove to be useful for monitoring other Descriptors of the MSFD.EU (European Space Agency) [308392, 21464/08/1-0, 607325]; Portuguese FCT [FRH/BD/78354/2011, SFRH/BD/78356/2011]; Horizon 2020 AquaSpace [633476]info:eu-repo/semantics/publishedVersio

Fabrication of lightweight ceramic mirrors by means of a chemical vapor deposition process

A process to fabricate lightweigth ceramic mirrors, and in particular, silicon/silicon carbide mirrors, involves three chemical vapor deposition steps: one to produce the mirror faceplate, the second to form the lightweight backstructure which is deposited integral to the faceplate, and the third and final step which results in the deposition of a layer of optical grade material, for example, silicon, onto the front surface of the faceplate. The mirror figure and finish are fabricated into this latter material

Method of fabricating lightweight honeycomb structures

A process is disclosed for fabricating lightweight honeycomb type structures out of material such as silicon carbide (SiC) and silicon (S). The lightweight structure consists of a core to define the shape and size of the structure. The core is coated with an appropriate deposit such as SiC or Si to give the lightweight structure strength and stiffness and for bonding the lightweight structure to another surface. The core is fabricated from extremely thin ribs of appropriately stiff and strong material such as graphite. First, a graphite core consisting of an outer hexagonal cell with six inner triangular cells is constructed from the graphite ribs. The graphite core may be placed on the back-up side of a SiC faceplate and then coated with SiC to produce a monolithic structure without the use of any bonding agent. Cores and methods for the fabrication thereof in which the six inner triangular cells are further divided into a plurality of cells are also disclosed

Matching and compressing sequences of visual hulls

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 61-63).In this thesis, we implement the polyhedral visual hull (PVH) algorithm in a modular software system to reconstruct 3D meshes from 2D images and camera poses. We also introduce the new idea of visual hull graphs. For data, using an eight camera synchronous system after multi-camera calibration, we collect video sequences to study the pose and motion of people. For efficiency in VH processing, we compress 2D input contours to reduce te number of triangles in the output mesh and demonstrate how subdivision surfaces smoothly approximate the irregular output mesh in 3D. After generating sequences of visual hulls from source video, to define a visual hull graph, we use a simple distance metric for pose by calculating Chamfer distances between 2D shape contours. At each frame of our graph, we store a view independent 3D pose and calculate the transition probability to any other frame based on similarity of pose. To test our approach, we synthesize new realistic motion by walking through cycles in the graph. Our results are new videos of arbitrary length and viewing direction based on a sample source video.by Naveen Goela.M.Eng

Estratégias de venda no mercado imobiliário: o papel da especialização pela angariação ou pela venda na produtividade do consultor em contexto de agência franchisada

Este estudo abordou o tema das estratégias de vendas no mercado imobiliário em Portugal. O seu objetivo foi compreender e identificar quais os fatores que influenciam o sucesso do consultor imobiliário. Em particular, procurou perceber-se a influência da especialização pelas transações de angariação (ou dedicação ao cliente proprietário) ou transações de venda (ou dedicação ao cliente comprador) no sucesso do consultor. Neste caso, o rendimento anual dos consultores foi considerado como proxy do seu sucesso. Foi construído um questionário para recolher os dados necessários para o estudo. Com base na amostra obtida, realizou-se uma análise exploratória onde foi possível perceber o perfil pessoal e profissional dos consultores. Depois, aplicou-se um modelo de regressão múltipla para estimar a influência do género, experiência de trabalho no mercado imobiliário e dos dois tipos de estratégia de especialização dos consultores (angariação ou venda) no rendimento anual do consultor. Os resultados mostraram que os fatores que causam um impacto positivo no rendimento do consultor estão relacionados o género dos consultores, com os anos de experiência no mercado imobiliário, e com as horas de dedicação ao cliente proprietário de imóveis. Além disso, observou-se que o género é o fator que mais contribui para a variabilidade do rendimento, seguido pela experiência e pelas horas de dedicação ao cliente proprietário. Neste último caso, os resultados indicaram que por cada hora adicional por semana de dedicação ao cliente proprietário, o rendimento anual do consultor poderá aumentar aproximadamente 2,74%. No entanto, as variáveis de especialização do consultor que foram calculadas através da razão entre angariações e o número total de transações revelaram não ser estatisticamente significativas para o rendimento anual dos consultores. O estudo teve um carácter inovador na realidade portuguesa, quer pelo próprio tema, quer pela introdução de novas variáveis para analisar os perfis dos consultores. No entanto, são recomendados estudos adicionais, nomeadamente a inclusão de mais agências do norte, centro e sul de Portugal, aumentando assim a dimensão da amostra. No contexto da mediação imobiliária em Portugal, este trabalho poderá contribuir para a escolha das estratégias a adotar por parte dos consultores imobiliários, com o objetivo de maximizar o seu rendimento pessoal, e fomentar o crescimento de empresas através de um nível mais estruturado dos seus recursos humanos.This study addressed the topic of sales strategies in the real estate market in Portugal. It aimed to understand and identify which factors influence the success of the real estate brokerage consultant. In particular, the influence of specialisation by the listing transactions (or dedication to the owner client) or sale transactions (or dedication to the buyer client) in the success of the consultant. In this case, the consultants' annual income was considered as a proxy of their success. The instrument used to collect the data was a questionnaire. Based on the obtained sample, an exploratory data analysis was conducted where it was possible to understand the personal and professional profiles of the real estate consultants. Furthermore, a multiple regression model was fitted to estimate the influence of gender, work experience in real estate and two consultant specialisation strategies (listing or selling) in the annual income of the consultant. The findings show that the factors that positively impact the performance of the agent are gender, work experience, and the hours dedicated to the owner client. In addition, gender is the factor that most contributes to the income variability, followed by the experience and hours of dedication to the owner client. In the latter case, the results indicated that for each additional hour per week dedicated to the owner client, the agent could increase its annual income by 2.74%. However, the indicators of specialisation determined through the ratio between listing transactions and the total number of transactions were not statistically significant to the annual income of the consultants. The study developed in this dissertation was innovative for the Portuguese case because of the theme itself, and because of the “new” questions that were included to analyse the profile of the agents. However, further work is recommended, such as planning the experiment in order to include several agencies from the north, centre and south of Portugal, thus increasing the sample size. In the context of the real estate industry in Portugal, this work might contribute to the choice of strategies to be adopted by real estate consultants, with the objective of maximizing their personal income and support the growth of companies with a more structured level of human resources

MERIS phytoplankton time series products from the SW Iberian Peninsula (Sagres) using seasonal-trend decomposition based on loess

The European Space Agency has acquired 10 years of data on the temporal and spatial distribution of phytoplankton biomass from the MEdium Resolution Imaging Spectrometer (MERIS) sensor for ocean color. The phytoplankton biomass was estimated with the MERIS product Algal Pigment Index 1 (API 1). Seasonal-Trend decomposition of time series based on Loess (STL) identified the temporal variability of the dynamical features in the MERIS products for water leaving reflectance ((w)()) and API 1. The advantages of STL is that it can identify seasonal components changing over time, it is responsive to nonlinear trends, and it is robust in the presence of outliers. One of the novelties in this study is the development and the implementation of an automatic procedure, stl.fit(), that searches the best data modeling by varying the values of the smoothing parameters, and by selecting the model with the lowest error measure. This procedure was applied to 10 years of monthly time series from Sagres in the Southwestern Iberian Peninsula at three Stations, 2, 10 and 18 km from the shore. Decomposing the MERIS products into seasonal, trend and irregular components with stl.fit(), the (w)() indicated dominance of the seasonal and irregular components while API 1 was mainly dominated by the seasonal component, with an increasing effect from inshore to offshore. A comparison of the seasonal components between the (w)() and the API 1 product, showed that the variations decrease along this time period due to the changes in phytoplankton functional types. Furthermore, inter-annual seasonal variation for API 1 showed the influence of upwelling events and in which month of the year these occur at each of the three Sagres stations. The stl.fit() is a good tool for any remote sensing study of time series, particularly those addressing inter-annual variations. This procedure will be made available in R software