Recent events have thrown the spotlight on infectious disease outbreak response. We developed a data-driven method, EpiGro, which can be applied to cumulative case reports to estimate the order of magnitude of the duration, peak and ultimate size of an ongoing outbreak. It is based on a surprisingly simple mathematical property of many epidemiological data sets, does not require knowledge or estimation of disease transmission parameters, is robust to noise and to small data sets, and runs quickly due to its mathematical simplicity. Using data from historic and ongoing epidemics, we present the model. We also provide modeling considerations that justify this approach and discuss its limitations. In the absence of other information or in conjunction with other models, EpiGro may be useful to public health responders. (C) 2016 The Authors. Published by Elsevier B.V.

Este trabalho tem como objetivo propor e avaliar um novo método para controle antissurto de compressores dinâmicos. É sabido que compressores dinâmicos são sujeitos ao fenômeno de surto, o qual pode danificar gravemente os componentes do compressor e provocar distúrbios de produção. O surto pode surgir a partir da ocorrência de distúrbios (por exemplo, fechamento da válvula de descarga do compressor) os quais, sem ação antissurto, fariam com que o ponto de operação se deslocasse para uma região de baixas vazões delimitada por uma linha conhecida como linha de surto. Portanto, compressores dinâmicos sempre são equipados com mecanismos antissurto: tipicamente uma válvula de reciclo de ação rápida controlada por um controlador PI antissurto. Dado que o surto se desenvolve extremamente rápido, usualmente não se permite que o compressor opere muito próximo da linha de surto. Esse objetivo de controle (manter o compressor afastado da linha de surto) é conflitante com objetivos de eficiência energética, pois os pontos de maior eficiência estão localizados próximos a essa linha. Logo, é desejável operar o compressor utilizando a mínima margem de surto que ainda garanta que a ação antissurto seja efetiva. Este trabalho propõe um método para ativação da ação antissurto no compressor com o objetivo de atingir uma ação mais rápida que o controle PI tradicional. O método proposto se baseia no cálculo offline das aberturas necessárias para a válvula de reciclo para cada possível combinação das posições dos atuadores do sistema, considerando um conjunto discreto pré-definido de valores dentro da faixa de valores de cada atuador. Esse processo gera uma tabela auxiliar para uso online. Os valores da tabela auxiliar são utilizados para gerar valores de referência para um controlador por realimentação, o qual é responsável por garantir que a trajetória do sistema irá do estado inicial no momento da ativação do controle antissurto para o estado estacionário desejado. Diversos cenários de distúrbio são simulados para diferentes controladores por realimentação e comparados com o controle antissurto PI tradicional. Os resultados mostram que a estratégia proposta é um candidato para melhorias na prática atual de controle antissurto, mas um controle por realimentação adequado deve ser selecionado e avaliado também considerando o aspecto de robustez, o qual é brevemente considerado no escopo deste trabalho. / This work aims at proposing and evaluating a novel method for anti-surge control of dynamic compressors. Dynamic compressors are known to suffer from surge, which can severely damage compressor components and disturb production. Surge may arise by the occurrence of disturbances (e.g. compressor discharge valve closure) that would bring its operating point to a region at low flows delimited by the so called surge line. Therefore, dynamic compressors are always equipped with anti-surge mechanisms: typically a fast actuating recycle valve controlled by a PI anti-surge controller. Since surge develops extremely fast, the compressor is usually not allowed to operate too close from the surge line. This control objective (keep the compressor away from the surge line) is conflicting with energy efficiency requirements, since higher efficiency operating points are located close to the surge line. Therefore, it is desirable to operate the compressor using the smallest possible surge margin that still guarantees anti-surge action is effective. This work proposes a method for triggering the compressor anti-surge action, aiming at a faster action than traditional PI control. The proposed anti-surge control method relies on an offline computation of necessary recycle valve openings for each possible combination of the system actuators positions, considering a predefined discrete set of values from the actuators positioning ranges. This generates a look-up table for online use. The values from the look-up table are used to identify the necessary compressor flow set-point for a feedback controller, which is responsible for ensuring that the system trajectory goes from the state upon anti-surge activation to the desired steady state. Several disturbance scenarios are simulated for different feedback controllers and compared to the traditional PI anti-surge controller. Results show that the proposed strategy is a candidate for improvements in current anti-surge control practice but an adequate feedback control strategy must be chosen and evaluated also under the consideration of robustness, which is slightly considered in the scope of this work.

The Mid-Atlantic coastal forests in Virginia are stressed by episodic disturbance from storms associated with hurricanes and nor'easters. Using annual tree ring data, we adopt a dendroclimatic and statistical modelling approach to understand the response and resilience of a coastal pine forest to slow progressive climate change and extreme storm surge events. Results indicate that radial growth of trees in the study area is influenced by age, vigor, competition, microsite variability, and regional climatic trends, but dominated periodically by disturbance due to storm surges. We evaluated seven local storm surge events to understand the effect of storm surges associated with nor'easters and hurricanes on radial growth. A general decline in radial growth was observed in the year of the storm and three years following it, after which the radial growth starts recovering. Given the projected increase in hurricanes and storm surge severity with changing global climate, this study contributes to understanding declining tree growth response and resilience of coastal forests to past disturbances. This can help predict vegetation response patterns to similar disturbances in the future.

Surge Free Added Resistance testing in variable head wave conditions were completed for a container ship model. The added resistance experiments include calm water, head wave, and oblique wave cases with a focus on establishing a validation benchmark for CFD codes computing the added resistance and motions of the ship model during maneuvering. The ship used is a 1/85.19 scale KRISO Container Ship, KCS, model with a length of 2.70 m. Tests were performed at the IIHR wave basin. The 20 x 40 x 4.5 m wave basin is equipped with 6 inline plunger type wave makers and a 3 degrees of freedom carriage. A 4 degrees of freedom, surge, heave, roll, and pitch free mount with a mass spring damper system was used to tow the model. Calm water tests were performed for 13 Froude numbers between 0.0867 and 0.2817. The resistance coefficients, sinkage, and trim were found for each test. The calm water results were obtained and compared to results from towing tank facilities, with traditional mounts, to estimate facility biases at the IIHR wave basin. The results show that the size difference of the IIHR model and surge free motion create magnitude differences between facilities. Head and oblique wave tests were performed at Froude number 0.26 and wave height to wavelength ratio, H/λ, of 0.0167. For all wave tests, time histories of wave amplitude, resistance, and 4 DOF were measured. Fourier analysis was completed for all time histories of waves, forces, and motions and the 0th, 1st, and 2nd harmonic amplitudes and phases are presented. All head wave results are compared to other facilities data taken in a towing tank with a traditional mount. The data from all wave heading data was analyzed with a focus on the trends with incremented wave encounter angle. Most harmonic amplitudes show good agreement between all facilities, but removal of the small model used by IIHR shows even better agreement between facilities. The oblique wave heading data shows good agreement with the only other experimental oblique wave added resistance testing. Complete uncertainty analysis was completed for select cases for calm water, head wave, and oblique wave conditions. The uncertainty showed accurate data form most wavelength settings.

More frequent and harsh storms coupled with sea level rise are affecting Canada’s sensitive coastlines. This research studies Isle Madame in Cape Breton, Nova Scotia which has been designated by Natural Resource Canada as a sea level rise vulnerable coastal community in Canada. The research models the spatial and temporal impacts of sea level rise from storm surge by focusing on identifying vulnerable areas in the community via geographical information systems (GIS) using ArcGIS, as well as modeling dynamic coastal damage via system dynamics using STELLA. The research evaluates the impacts in terms of the environmental, social, cultural, economic pillars that profile the coastal community for a series of modelled Storm Scenarios. This research synthesizes information from a variety of sources including the coastal ecology and natural resources, as well as human society and socioeconomic indicators included in the four mentioned pillars. The objective of the research is to determine vulnerable areas on Isle Madame susceptible to storm damage, and consequently, to improve local community knowledge and preparedness to more frequent harsh storms. This research therefore presents a dynamic model for the evaluation of storm impacts in Isle Madame designed with the goal to help the community ultimately to plan and implement a strategy to adapt to pending environmental change.

More frequent and harsh storms coupled with sea level rise are affecting Canada’s sensitive coastlines. This research studies Isle Madame in Cape Breton, Nova Scotia which has been designated by Natural Resource Canada as a sea level rise vulnerable coastal community in Canada. The research models the spatial and temporal impacts of sea level rise from storm surge by focusing on identifying vulnerable areas in the community via geographical information systems (GIS) using ArcGIS, as well as modeling dynamic coastal damage via system dynamics using STELLA. The research evaluates the impacts in terms of the environmental, social, cultural, economic pillars that profile the coastal community for a series of modelled Storm Scenarios. This research synthesizes information from a variety of sources including the coastal ecology and natural resources, as well as human society and socioeconomic indicators included in the four mentioned pillars. The objective of the research is to determine vulnerable areas on Isle Madame susceptible to storm damage, and consequently, to improve local community knowledge and preparedness to more frequent harsh storms. This research therefore presents a dynamic model for the evaluation of storm impacts in Isle Madame designed with the goal to help the community ultimately to plan and implement a strategy to adapt to pending environmental change.

This study presents an unsteady-state hydraulic model analysis of hurricane storm surge and rainfall-runoff interactions in the Clear Creek Watershed, a basin draining into Galveston Bay and vulnerable to flooding from both intense local rainfalls and storm surge. Storm surge and rainfall-runoff have historically been modeled separately, and thus the linkage and interactions between the two during a hurricane are not completely understood. This study simulates the two processes simultaneously by using storm surge stage hydrographs as boundary conditions in the Hydrologic Engineering Center’s – River Analysis System (HEC-RAS) hydraulic model. Storm surge hydrographs for a severe hurricane were generated in the Advanced Circulation Model for Oceanic, Coastal, and Estuarine Waters (ADCIRC) model to predict the flooding that could be caused by a worst-case scenario. Using this scenario, zones have been identified to represent areas in the Clear Creek Watershed vulnerable to flooding from storm surge, rainfall, or both.

Given the past history and future risk of storm surge in the United States, alternative storm protection techniques are needed to protect vital sectors of the economy and population, particularly within southeastern Louisiana. It is widely hypothesized that coastal wetlands offer protection from storm surge and wave action, though the extent of this protection is unknown due to the complex physics behind vegetated flow dynamics. This thesis presents numerical modeling results that estimate the relative sensitivity of waves and storm surge to characteristics embodied by coastal wetlands. An idealized grid domain and 400 km2 (20 km by 20 km) marsh feature provide a controlled environment for evaluating marsh characteristics, including bottom friction, elevation, and continuity. Marsh continuity is defined as the ratio of healthy marsh area to open water area within the total wetland area. It is determined that increased bottom friction reduces storm surge levels and wave heights. Through the roughening of the bottom from sandy to covered with tall grass, it is estimated that waves may be dampened by up to 1.2 m at the coast, and peak surge may be reduced by as much as 35%. The lowering of marsh elevation generally increases wave heights and decreases surge levels, as expected. A 3.5 m decrease in marsh elevation results in as much as a 2.6 m increase in wave height, and up to a 15% decrease in surge levels. Reductions in marsh continuity enhance surge conveyance into and out of the marsh. For storms of low surge potential, surge is increased by as much as 70% at the coast due to decreasing marsh continuity from 100% to 50%, while for storms of high surge potential, surge is decreased by 5%. This indicates that for storms of high surge potential, a segmented marsh may offer comparable surge protection to that of a continuous marsh. Wave heights are generally increased within the marsh due to the transmission of wave energy through marsh channels. Results presented in this thesis may assist in the justification of coastal wetland mitigation, and optimize marsh restoration in terms of providing maximum storm protection.

Since the devastating hurricane seasons of 2004, 2005, and 2008, the stability and serviceability of coastal bridges during and following hurricane events have become a main public concern. Twenty coastal bridges, critical for hurricane evacuation and recovery efforts, in Texas have been identified as vulnerable to hurricane surge and wave action. To accurately assess extreme surges at these bridges, a dimensionless surge response function methodology was adopted. The surge response function defines maximum surge in terms of hurricane meteorological parameters such as hurricane size, intensity, and landfall location. The advantage of this approach is that, given a limited set of discrete hurricane surge data (either observed or simulated), all possible hurricane surges within the meteorological parameter space may be described. In this thesis, we will first present development of the surge response function methodology optimized to include the influence of regional continental shelf geometry. We will then demonstrate surge response function skill for surge prediction by comparing results with surge observations for Hurricanes Carla (1961) and Ike (2008) at several stations along the coast. Finally, we apply the improved surge response function methodology to quantify extreme surges for Texas coastal bridge probability and vulnerability assessment.

No description available.