Understanding the relative importance of vertical and horizontal flow in ice-wedge polygons

Ice-wedge polygons are common Arctic landforms. The future of these landforms in a warming climate depends on the bidirectional feedback between the rate of ice-wedge degradation and changes in hydrological characteristics. This work aims to better understand the relative roles of vertical and horizontal water fluxes in the subsurface of polygonal landscapes, providing new insights and data to test and calibrate hydrological models. Field-scale investigations were conducted at an intensively instrumented location on the Barrow Environmental Observatory (BEO) near Utqiagvik, AK, USA. Using a conservative tracer, we examined controls of microtopography and the frost table on subsurface flow and transport within a low-centered and a high-centered polygon. Bromide tracer was applied at both polygons in July 2015 and transport was monitored through two thaw seasons. Sampler arrays placed in polygon centers, rims, and troughs were used to monitor tracer concentrations. In both polygons, the tracer first infiltrated vertically until encountering the frost table and was then transported horizontally. Horizontal flow occurred in more locations and at higher velocities in the low-centered polygon than in the high-centered polygon. Preferential flow, influenced by frost table topography, was significant between polygon centers and troughs. Estimates of horizontal hydraulic conductivity were within the range of previous estimates of vertical conductivity, highlighting the importance of horizontal flow in these systems. This work forms a basis for understanding complexity of flow in polygonal landscapes

Comportamento sísmico de edifícios assimétricos de alvenaria estrutural : ensaios na mesa sísmica

O objetivo principal deste trabalho consiste na avaliação do desempenho sísmico de um sistema em alvenaria armada que possa ser representativo da construção corrente de edifícios de pequeno a médio porte em zonas de moderada a elevada perigosidade sísmica. Pretendeu-se avaliar o efeito da complexidade da geometria em planta bem como a influência do reforço aplicado ao nível das juntas horizontais e verticais. Para o efeito, foram construídos dois modelos de edifícios de alvenaria armada e não armada à escala reduzida (1:2) com a solução em alvenaria estrutural em blocos de betão com furação vertical. Estes modelos de edifícios foram posteriormente sujeitos a uma ação sísmica regulamentar característica da região de Lisboa na mesa sísmica do Laboratório nacional de Engenharia Civil

Experimental and numerical analysis of the seismic performance of concrete block masonry buildings

The increase in housing demand and the construction cost of the necessary houses for its satisfaction have motivated the study of economical and efficient solutions aiming at developing new construction methods. A new solution for the construction of residential houses is presented. Dynamic seismic tests by using a shaking table were performed on two masonry buildings. The first experimental model incorporates steel reinforcement according to the Eurocodes, while the second was tested as an unreinforced solution. A numerical model for the unreinforced solution was prepared by using macro-modelling approach. Five non-linear phased dynamic analyses with time integration representing the same seismic amplitude tests implemented during the experimental campaign were made. In terms of experimental results, the quantitative parameters for both models and the crack patterns are presented. Comparisons between the experimental results and those from the numerical simulations are also presented.Portuguese Agency of Innovation (ADI)

Chemical changes of heat treated pine and eucalypt wood monitored by FTIR

A hardwood, Eucalyptus globulus Labill., and a softwood Pinus pinaster Aiton., were heat treated at temperatures between 170 and 210ºC in an oven and in an autoclave. The samples were pre-extracted with dichloromethane, ethanol and water and ground prior to Fourier Transform Infrared (FTIR) spectroscopic analysis. The heat treatment caused significant changes in the chemical composition and structure of wood, in lignin and polysaccharides. Hemicelluloses were the first to degrade as proved by the initial decrease of the 1730 cm-1 peak due to the breaking of acetyl groups in xylan. Hardwood lignin changed more than softwood lignin, with a shift of maximum absorption from 1505 cm-1 to approximately 1512 cm-1 due to decrease of methoxyl groups, loss of syringyl units or breaking of aliphatic side-chains. The macromolecular structure becomes more condensed and there is a clear increase of non-conjugated (1740 cm-1) in relation to conjugated groups (1650 cm-1). However, the changes induced by the thermal treatment are difficult to monitor by FTIR spectroscopy due to the different chemical reactions occurring simultaneously.info:eu-repo/semantics/publishedVersio

Infinite dynamic bayesian networks

We present the infinite dynamic Bayesian network model (iDBN), a nonparametric, factored state-space model that generalizes dynamic Bayesian networks (DBNs). The iDBN can infer every aspect of a DBN: the number of hidden factors, the number of values each factor can take, and (arbitrarily complex) connections and conditionals between factors and observations. In this way, the iDBN generalizes other nonparametric state space models, which until now generally focused on binary hidden nodes and more restricted connection structures. We show how this new prior allows us to find interesting structure in benchmark tests and on two realworld datasets involving weather data and neural information flow networks.Massachusetts Institute of Technology (Hugh Hampton Young Memorial Fund Fellowship)United States. Air Force Office of Scientific Research (AFOSR FA9550-07-1-0075

Nonparametric Bayesian Policy Priors for Reinforcement Learning

We consider reinforcement learning in partially observable domains where the agent can query an expert for demonstrations. Our nonparametric Bayesian approach combines model knowledge, inferred from expert information and independent exploration, with policy knowledge inferred from expert trajectories. We introduce priors that bias the agent towards models with both simple representations and simple policies, resulting in improved policy and model learning

Precoded generalized spatial modulation for downlink MIMO transmissions in beyond 5G networks

The design of multiple input multiple output (MIMO) schemes capable of achieving both high spectral and energy efficiency constitutes a challenge for next-generation wireless networks. MIMO schemes based on generalized spatial modulations (GSM) have been widely considered as a powerful technique to achieve that purpose. In this paper, a multi-user (MU) GSM MIMO system is proposed, which relies on the transmission of precoded symbols from a base station to multiple receivers. The precoder’s design is focused on the removal of the interference between users and allows the application of single-user GSM detection at the receivers, which is accomplished using a low-complexity iterative algorithm. Link level and system level simulations of a cloud radio access network (C-RAN) comprising several radio remote units (RRUs) were run in order to evaluate the performance of the proposed solution. Simulation results show that the proposed GSM MU-MIMO approach can exploit efficiently a large number of antennas deployed at the transmitter. Moreover, it can also provide large gains when compared to conventional MU-MIMO schemes with identical spectral efficiencies. In fact, regarding the simulated C-RAN scenario with perfect channel estimation, system level results showed potential gains of up to 155% and 139% in throughput and coverage, respectively, compared to traditional cellular networks. The introduction of imperfect channel estimation reduces the throughput gain to 125%.info:eu-repo/semantics/publishedVersio