259 research outputs found
Os papéis semânticos Experienciador e Causador nos sintagmas nominais com adjectivos psicológicos
No full textinfo:eu-repo/semantics/publishedVersio
Os papéis semânticos Experienciador e Causador nos sintagmas nominais com adjectivos psicológicos
No full textinfo:eu-repo/semantics/publishedVersio
Control and simulation of power converters for HVDC grids
No full textHigh Voltage Direct Current (HVDC) is a growing technology due to the necessities of electric connection between islands, offshore wind farms, oil platforms, the electrification of transports and other future applications in the electric sector. This work presents a methodology that is used to design the control of the multi-terminal HVDC grids interconnecting offshore wind farms with the main onshore electrical grid.
The methodology is detailed in this Thesis also including relevant information about converters and HVDC is presented. First, two simple models are analyzed to illustrate the studied control system, the first one is the Voltage Source Converter (VSC) operating in power control mode and the second one is the VSC grid converter operating in DC voltage control mode.
Moreover, the control design methodology is applied in a case of a multi-terminal HVDC grid formed by four terminals. The main objective is to analyze the best range of values of the DC primary voltage regulator considering the limitations for each electrical magnitude during both the transient response and the steady state. To perform this analysis, several scenarios have been evaluated through simulation models using the software Matlab-Simulink®.
Note: The schemes, the code and the graphs that have been performed in Matlab-Simulink® are shown and explained in the Annexes document. The files created in Matlab-Simulink® to perform this Thesis has been uploaded to the online repository GitHub. The files are available at https://github.com/silos94/TFM-Victor-Silos-Sanchez. Nevertheless, for space limitations, the files extracted from simulations, which they are composed by figures and data, could not be uploaded to GitHub. Please, feel free to contact the author about any issue
Control and simulation of power converters for HVDC grids
No full textHigh Voltage Direct Current (HVDC) is a growing technology due to the necessities of electric connection between islands, offshore wind farms, oil platforms, the electrification of transports and other future applications in the electric sector. This work presents a methodology that is used to design the control of the multi-terminal HVDC grids interconnecting offshore wind farms with the main onshore electrical grid.
The methodology is detailed in this Thesis also including relevant information about converters and HVDC is presented. First, two simple models are analyzed to illustrate the studied control system, the first one is the Voltage Source Converter (VSC) operating in power control mode and the second one is the VSC grid converter operating in DC voltage control mode.
Moreover, the control design methodology is applied in a case of a multi-terminal HVDC grid formed by four terminals. The main objective is to analyze the best range of values of the DC primary voltage regulator considering the limitations for each electrical magnitude during both the transient response and the steady state. To perform this analysis, several scenarios have been evaluated through simulation models using the software Matlab-Simulink®.
Note: The schemes, the code and the graphs that have been performed in Matlab-Simulink® are shown and explained in the Annexes document. The files created in Matlab-Simulink® to perform this Thesis has been uploaded to the online repository GitHub. The files are available at https://github.com/silos94/TFM-Victor-Silos-Sanchez. Nevertheless, for space limitations, the files extracted from simulations, which they are composed by figures and data, could not be uploaded to GitHub. Please, feel free to contact the author about any issue
Using taxi GPS data for macroscopic traffic monitoring in large scale urban networks: Calibration and MFD derivation
No full textA two-Fluid Model (TFM) of urban traffic provides the macroscopic description of traffic state. The TFMs parameters are hard to calibrate, particularly for the dynamic traffic conditions. This leads to the TFM often being used to compare the quality of service through the plot of stopping time versus trip time of the vehicles in the network. Recently, the taxi GPS data has been applied to predict the traffic condition at the network level. Despite the network-wide coverage of the taxi GPS probe data, the penetration rate of taxis in the network traffic is still a vital and challenging issue for traffic estimation purpose. It is necessary to estimate penetration rate of taxis by combining with other data sources. Here, we propose a novel approach to fill two gaps: TFM parameter calibration and the taxis penetration rate. This method stretches the description of TFM to a zone size. The method is applied to real Changsha city GPS data, calibrating the parameters. The macroscopic fundamental diagram of the large-scale city is derived. For the Changsha case, running speed is the super-linear power law of the fraction of running cars; the fraction of stopping time is nearly linear power law of density, which can be an alternative of the density. The proposed method enables the calibration of TFM parameters and macroscopic traffic monitoring at urban scale using only GPS data.Transport and Plannin
Androgen insensitive male rats display increased anxiety-like behavior on the elevated plus maze
No full textMale rats carrying the testicular feminization mutation (Tfm-affected males) are insensitive to androgens, resulting in a female-typical peripheral phenotype despite possession of inguinal testes that are androgen secretory. Androgen-dependent neural and behavioral processes may likewise show atypical sexual differentiation. Interestingly, these mutant rats display elevated serum corticosterone, suggesting a chronic anxiety phenotype and dysregulated hypothalamic–pituitary–adrenal axis. In order to understand if elevated anxiety-like behavior is a possible mediating variable affecting the display of certain androgen-dependent behaviors, we compared the performance of Tfm-affected males to wild type males and females in the elevated plus maze (EPM). Two well-established indicators of anxiety-like behavior in the EPM were analyzed: total percentage of time spent on the open arms, and the percentage of open arm entries. We also analyzed the total number of open arm entries. Interestingly, Tfm-affected males spent less percentage of time on the open arms than both males and females, suggesting increased anxiety-like behavior. Percentage of open arm entries and the total number of arm entries was comparable between the groups, indicating that the observed decrease in the percentage of time spent on the open arms was not due to a global reduction in exploratory behavior. These data, in contrast to earlier reports, thus implicate androgen receptor-mediated functions in the expression of anxiety behaviors in male rats. Given that anxiety is widely reported as a precipitating factor in depression, studying the role of the androgen receptor in anxiety may give insights into the pathogenesis of major depressive disorder.Peer reviewedFinal article publishedTestosteroneTesticular feminization mutationSex differenceDepressionAndrogen recepto
Simulating a lake as a high-conductivity variably saturated porous medium
No full textOne approach for simulating ground water-lake interactions is to incorporate the lake into the ground water solution domain as a high-conductivity region. Previous studies have developed this approach using fully saturated models. This study extends this approach to variably saturated models, so that ground water-lake interactions may be more easily simulated with commonly used or public domain variably saturated codes that do not explicitly support coupled lake-water balance modeling. General guidelines are developed for the choices of saturated hydraulic conductivity and moisture retention and relative permeability curves for the lake region. When applied to an example ground water-lake system, model results are very similar to those from a model in which the lake is represented as a specified head boundary continuously updated by a lake mass balance. The high-conductivity region approach is most suitable for relatively simple geometries and lakes with slower and smaller fluctuations when the overall flow pattern and system fluxes, rather than the detailed flow pattern around the intersection of the lake and land surfaces, are of interest. © 2008 The Author(s).link_to_subscribed_fulltex
- …
