263 research outputs found
Modeling, Control, and Operation of an M-DAB DC-DC Converter for Interconnection of HVDC Grids
No full textFuture high-voltage direct-current (HVDC) networks based on voltage source converters (VSCs) will have different structures (asymmetric monopolar, bipolar, or symmetric monopolar), voltage levels, control, and protection schemes. Therefore, dc-dc converters are needed to interconnect those VSC-HVDC grids and several technical issues on their control and operational systems must be adequately addressed. A dc-dc converter based on a modular-dual active bridge (M-DAB) converter is suggested to reach a desirable interconnection of the HVDC grids and regulate power flow (PF) between them. A dynamic averaged model is proposed for the M-DAB converter and its stability is analyzed using the Lyapunov function. Moreover, a new local controller based on nonlinear control theory is proposed for the M-DAB. The new M-DAB local controller is integrated with the energy management system (EMS), by updating the PF equations, to create a complete control structure. Considering the CIGRE DCS3 HVDC test system and the studied M-DAB, static, dynamic simulation, and experimental studies are conducted and the dc-dc converter and the performance of the designed controllers and the EMS are examined and validated.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power Grid
Les marqueurs de prolifération en oncologie vétérinaire : applications à l'étude pronostique du mastocytome cutané canin
No full textLe mastocytome cutané représente un type tumoral dominant de la cancérologie du chien mais demeure l'une des tumeurs canines au comportement clinique les plus imprévisibles. L'auteur évalue dans une étude rétrospective portant sur 120 chiens porteurs de mastocytome cutané, la valeur pronostique de la détection immunohistochimique des marqueurs de prolifération PCNA et Ki-67. Il montre que la détermination de l'expression de l'antigène Ki-67 permet de prédire avec une grande fiabilité l'évolution clinique post-chirurgicale de ce type tumoral
Cold adapted and closely related mucoraceae species colonise dry-aged beef (DAB)
No full textThe dry ageing is a historically relevant method of meat preservation, now used as a way to produce the dry-aged beef (DAB) known for its pronounced flavour. Partially responsible for the taste of the DAB may be various microorganisms that grow on the surface of the meat. Historically, the fungal species colonising the DAB were described as members of the genera Thamnidium and Mucor. In this study we used both culture based approach as well as ITS2 rDNA metabarcoding analysis to investigate the fungal community of the DAB, with special emphasis on the mucoralean taxa. Isolated fungi were members of 6 different species from the family Mucoraceae, belonging to the genera Mucor and Helicostylum. Metabarcoding data provided supplementary information regarding the presence of other fungi including those from the Thamnidium genus. In both approaches used in this study isolates closely related to the Mucor flavus strain CBS 992.68 dominated. © 2023 The Author
Impact of Electrolyzer on the Operation of a Dual Active Bridge Converter
No full textElectrolysis requires a high DC current at low voltage to produce hydrogen from water. Designing power converters for such a load requirement could be challenging while fulfilling the galvanic isolation needs. Therefore, prior knowledge of the electrolyzer's impact on the converter operation should be needed. In this context, this paper investigates the behavior of the Dual Active Bridge (DAB) converter when utilized for electrolysis. A MATLAB simulation of DAB with a 10 kW alkaline electrolyzer is developed. Several converter parameters, such as the phase shift angle, series inductance, peak and RMS currents, and voltage gain, are analyzed during electrolysis. Distinct operating behavior is observed from the analysis.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
Dependencia emocional y adicción al sexo en una comunidad LGBT y heterosexuales
No full textResumen (analítico): La investigación desarrollada de diseño descriptivo correlacional simple, tuvo como objetivo general relacionar la dependencia emocional y la adicción al sexo en una muestra de 37 heterosexuales y 15 participantes una comunidad LGBT de la ciudad de Trujillo, tuvo como objetivo evidenciar la relación entre la dependencia emocional y la adicción al sexo, por lo cual se utilizó el Cuestionario de dependencia emocional y el Instrumento de medición de adicción al sexo. Los resultados obtenidos evidencian que existe diferencias estadísticamente significativas según identidad sexual en la variable adicción al sexo con puntuaciones más altas en los participantes de la comunidad LGBT, asimismo en la población heterosexual la adicción al sexo y fetichismo reporta una relación directa estadísticamente significativa con la dependencia emocional, además en la comunidad LGBT se reporta una relación directa estadísticamente significativa con la dependencia emocional y la dimensión ansiedad de separación, asimismo entre fantasías sexuales y expresión limite alcanza una relación directa estadísticamente significativa.
A Dual Active Bridge Converter with an Extended High-Efficiency Range by DC Blocking Capacitor Voltage Control
No full textA Dual Active Bridge (DAB) converter can achieve a wide high-efficiency range when its input and output voltages are equal, assuming a 1:1 turns ratio for its isolation transformer. If its input or output voltage is doubled, efficiency of the DAB will drop significantly, because of the introduction of hard switching and high circulating power. Thus, a new modulation scheme has been proposed, whose main idea is to introduce a voltage offset across the dc blocking capacitor connected in series with the transformer. Operational principle of the proposed modulation has been introduced, before analyzing its soft-switching area and circulating power mathematically. The final modulation scheme is not difficult to implement, but can help the DAB achieve soft switching, low circulating power, and thereby high efficiency, even with its input or output voltage doubled.These features have been verified by experimental results obtained with a 1.2 kW prototype.Accepted Author ManuscriptDC systems, Energy conversion & Storag
Modelos alométricos de biomasa de árboles de Guazuma crinita Mart en plantaciones forestales de Ucayali, Perú
No full textThe white ball (Guazuma crinita Mart, Meliaceae) as one of the most important species in the Ucayali region due to its rapid growth and increasing market value, makes it a competitive species when choosing species for a program of production of goods and sustainable services, therefore determining the amount of biomass plays a key role for this purpose; In this purpose, the 38 trees of G. crinita at 31 months of age, with an average diameter at the height of the base of 13.33 cm, with a maximum and minimum value of 17.4 and 10.2 cm, respectively, with a standard deviation of 1.80 cm and a variability coefficient of 13%, for an average total biomass of 28.76 Kg, with a standard deviation of 10.07 and a variability coefficient of 35%; It was determined that there is a high relationship between the independent variable diameter at the height of the base (dab) and the total aerial biomass of the trees in the Aguaytia river basin according to the biomass model ~ a*dab^b, which resulted which is predictable with the following formula Bmadab = 0.04253*dab2.5027 with R2 = 0.9397.
La bolaina blanca (Guazuma crinita Mart, Meliaceae) es una de las especies más importantes de la región Ucayali por su rápido crecimiento y creciente valor en el mercado, convirtiéndola en una especie competitiva al momento de elegir especies para un programa de producción de bienes y servicios sostenible, por ello la determinación de la cantidad de biomasa cumple un papel clave para este fin; en este contexto, fueron evaluados 38 árboles de G. crinita de 31 meses de edad, con diámetro promedio a la atura de la base de 13,33 cm, con un valor máximo y mínimo de 17,4 y 10,2 cm, respectivamente, con desviación estándar de 1,80 cm y un coeficiente de variabilidad de 13%, para una biomasa total promedio de 28,76 Kg, con una desviación estándar de 10,07 y un coeficiente de variabilidad del 35%; se determinó que en la cuenca del río Aguaytia existe una alta relación entre la variable independiente diámetro a la altura de la base (dab) y la biomasa total aérea de los árboles de acuerdo al modelo biomasa ~ a*dab^b, lo que resultó que es previsible con la siguiente fórmula Bmadab=0,04253*dab2,5027 con R2= 0,9397
Consumo de sustancias psicoactivas y trastornos de la personalidad: estudio comparativo entre personas consumidoras y no consumidoras
No full textEl estudio de la personalidad en sujetos adictos es clave para comprender la relación que media entre el sujeto, la droga y el ambiente. Las investigaciones que se han realizado en Colombia sobre este tema han estado centradas en la correspondencia entre el consumo y la personalidad normal; sin embargo, en el ámbito internacional, se insiste en la importancia de ampliar el marco comprensivo hacia las relaciones entre el consumo y los trastornos de la personalidad. El objetivo de este estudio fue identificar diferencias en el perfil de trastornos de personalidad de sujetos pertenecientes a una comunidad terapéutica para el tratamiento del consumo de sustancias psicoactivas de la ciudad de Bogotá-Colombia y población de comparación. Para este estudio participaron 30 personas con edades comprendidas entre los 17 y los 28 años. Se utilizó, para evaluar el nivel de consumo de sustancias, la Escala CRAFFT (CARLOS) y, para evaluar los trastornos de la personalidad, el Inventario Multifásico de la Personalidad de Minnesota (MMPI-2). Los resultados muestran relaciones importantes entre el consumo y diversos rasgos de la personalidad; resaltan las relaciones encontradas en las escalas de desviación psicopática y esquizofrenia, lo que haría pensar en el nexo entre el consumo y las conductas de oposición a la norma. A diferencia de otros estudios, en este se encuentran bajos puntajes en la escala de depresión en consumidores, lo que podría señalar una característica propia de la población en tratamiento. Frente a la variable género y consumo en estas comunidades, la evidencia sigue siendo mixta.</jats:p
Dual Active Bridge Converter with PWM Control In Solid State Transformer Application
No full textabstract: For the solid-state transformer (SST) application, a three-stage configuration consisting of a PWM rectifier based AC/DC stage, a dual active bridge (DAB) converter based DC/DC stage and a PWM inverter based DC/AC stage offers several advantages. For single-phase SST, the instantaneous input and load power seen by the DC/DC stage varies from zero to twice the load average power at double the line frequency. Traditionally, with phase-shift control, large DAB DC link capacitors are used to handle the instantaneous power variation of the load, with the DAB converter processing only the load average power resulting in better soft-switching range and consequently high efficiency. However, the large electrolytic capacitors required adversely affect the power density and the reliability of SST. In this thesis, a PWM control is used for the DAB converter in SST, which extends the ZVS range of DAB and allows the DAB converter to handle the pulsating power while maintaining/improving efficiency. The impact of the output capacitance of switches with PWM control is discussed for practical implementation. A 40kHz, 500W DAB converter is designed and built, and the experimental results proves that the DAB converter with PWM control in SST can achieve comparable efficiency while the DC link capacitors of SST can be reduced to a value that electrolytic capacitors are not required.Dissertation/ThesisM.S. Electrical Engineering 201
Transformer Current Ringing in Dual Active Bridge Converters
No full textIn dual active bridge (DAB) converters, there can be transformer current ringing, especially when the transformer turns ratio is high. It is induced by high dv/dt generated by fast switching as well as the low impedance of the magnetic tank at the high-frequency range. To quantify the influence of the magnetic tank, its impedance model is thoroughly modeled by considering all the parasitic components. It is found that the parasitic capacitors of the magnetics do not equally affect the current ringing, and thereby the critical one is addressed. On top of that, the design guide of the inductor is provided for the mitigation of the current ringing. Additionally, the impact of dv/dt is also studied. The models and analyses are verified on a 2.5-kW DAB prototype.DC systems, Energy conversion & Storag
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