283 research outputs found
Modeling and Control of the Falling Film Evaporator Process
Wegen ihres energieeffizienten Betriebs und flexiblen Designs haben Fallfilmverdampfer (FFV) eine breite Anwendung in der Industrie.
Neben Fragen zur Konstruktion sind dominante Totzeiten herausfordernd bzgl. Prozessmodellierung und -regelung.
Insbesondere erfordert die Automatisierung von Produktionssystemen digitale Zwillinge, d.h. Anlagenmodelle, um Betreiber zu schulen oder den Designprozess zu beschleunigen.
Das Herz eines FFV besteht aus Rohren, an deren Innenseiten verdampfender Flüssigkeitsfilm hinabläuft.
Daher sind die Rohre primäre Quelle für Totzeiten, welche sich vornehmlich auf den Transport wichtiger Prozessgrößen wie Liquidkonzentration und Massenstrom beziehen.
Allerdings ist die Modellierung des entsprechenden dynamischen Verhaltens schwierig.
Aus Sicht der Regelung erzeugen Totzeiten Schwingungen der Ausgangskonzentration - im Speziellen während der Anfahrprozesse.
Zusätzlich verkomplizieren starke Kopplungen zwischen Ausgangsmassenstrom und -konzentration die in modernen Produktionen erforderliche Mehrgrößenregelung.
Die vorliegende Arbeit präsentiert Lösungen für alle genannten Herausforderungen.
Durch Gliederung des FFV-Prozesses in Teilsysteme sind verschiedene Designs in einfacher Weise simulierbar.
In diesem Kontext erfolgt die Validierung eines bestimmtes Anlagenmodell auf Basis von Realdaten, was zum digitalen Zwilling führt.
Zur Entwicklung neuer Transportmodelle verdampfender Flüssigkeitsfilme werden Bilanzgleichungen ausgewertet, sodass Systeme hyperbolischer partieller Differentialgleichungen entstehen.
Mittels des Charakteristikenverfahrens gelingt eine Transformation in Totzeitgleichungen; letztere sind für Simulation und Reglerentwurf vorteilhaft.
Pilotanlagenexperimente zur Identifikation und Validierung eines ausgewählten Modells unterstreichen die Eignung des Ansatzes, das gemessene Ein-/Ausgangsverhalten abzubilden.
Zur Beantwortung regelungstechnischer Fragen wird ein einfaches Prozessmodell entwickelt, das Zuordnungsproblem gelöst und ein Mehrgrößenregelungskonzept entworfen
Control of Solar Thermal Linear Fresnel Collector Plants in Single Phase and Direct Steam Generation Modes
Ein wesentlicher Unterschied erneuerbarer Energiequellen zu fossilen Energieträgern
liegt in der zeitlichen Verfügbarkeit. Im Gegensatz zu fossil
angetriebenen Prozessen lässt sich die Energiezufuhr nicht regeln. Dies
stellt vor allem die Solarenergie vor eine wesentliche Herausforderung. Die
Sonne als Energiequelle unterliegt nicht nur tages bzw. jahreszeitlichen
Schwankungen, sie ist oft auch nicht vorhersehbar. Dieser scheinbar kleine
Unterschied zur fossilen Energiegewinnung, hat zu weitreichenden Forschungsak
tivitäten in verschiedenen Bereichen der Wissenschaft und des Ingenieurwesens
geführt, darunter die Entwicklung von Speichertechnologien und
hybrider Systeme, die Abbildung des dynamischen Verhaltens, insbesondere
im Teillastbetrieb und nicht zu Letzt die entsprechende Ausarbeitung
verschiedener Regelsysteme.
Das Hauptziel der vorliegenden Arbeit ist die Entwicklung geeigneter
Regelgesetze für solarthermische Anlagen um der intermittierenden Natur
der Sonne als Energieressource gerecht zu werden. Eine gute Regelung
erhöht den Solarertrag, reduziert Stillstände, bietet eine optimierte Wahl
des Betriebspunktes und garantiert die Stabilität und Robustheit des Systems,
mit der Personen und Anlagensicherheit als oberste Priorität.
Die Thesis gliedert sich in zwei Hauptteile. Der erste Teil beinhaltet
die Regelungstechnik konzentrierender, solarthermischer Systeme mit einphasigen
Strömungen. Als wesentliche Regelgröße dient die Kollektoraustritttemperatur.
Mehrere Regelsysteme wurden unter verschiedenen Rahmenbedingungen und
Prozessanforderungen experimentell getestet. Eine erweiterte PID-Regelung
mit geeigneten Vorsteuerungsschleifen zeigt sehr gute Resultate, zudem lässt
sich die Gestaltung und Umsetzung des Regelsystems einfach halten.
Der zweite Teil der Arbeit widmet sich dem Regelsystem im solaren
Direktverdampfungsbetrieb. Hierbei ist die Hauptregelgröße der benötigte
Dampfdruck an der Prozessschnittstelle. Im Direktverdampfungsbetrieb
wird die Anlage als Mehrgrößenregelsystem betrachtet. Zwei Regelkonzepte
wurden mit der vorliegenden Arbeit entwickelt und getestet. Eines der
Konzepte basiert auf einer erweiterten PID-Regelung mit Vorsteuerung.
Dieses wurde erfolgreich umgesetzt und unter Realbedingungen über mehrere
Jahre intensiv getestet. Das zweite Konzept stützt sich auf die Theorie der
modellbasierten, Modellprädiktive Regelung (MPC). Hierbei handelt es sich
um ein komplexes, entwicklungsintensives, Regelkonzept. Der wesentliche
Vorteil ist die universelle Anwendbarkeit, mit reduziertem Aufwand für
Implementierung, Bewirtschaftung und Inbetriebnahme.
Die vorliegende Thesis zeigt, dass sich trotz der komplexen Dynamik
solarthermischer Grossanlagen mit den vorgeschlagenen Regelkonzepten
eine zuverlässige, robuste und wartungsarme Energieversorgung bewerkstelligen lässt
Advanced Process Control with Applications in the Food Industry
Due to the requirements for enhanced food safety and different nutrient demand for customers, food process control is becoming an increasingly important issue in the food industry. Many advanced control methods, like adaptive control, predictive control, robust control and fuzzy logic control, have attracted increasing attention and there are many successful applications in the manufacture of dairy products in the last two decades. Applying a multi-effect falling film evaporator to remove the water from the liquid is widely used in the dairy industry. This thesis addresses some key issues concerning dairy evaporation process control which include system modelling, controller development and optimization as well as the results comparison.
Fundamentally, this thesis presents a study of three effects of falling film evaporator for the milk concentration process in the dairy industry as an example. The main aim, however, is to research, develop and demonstrate different advanced control strategies, such as model predictive control (MPC) and fuzzy logic control (FLC), applied to the evaporator system for the process control purposes. They both can deal with the complex non-linear processes. But MPC can maintain the system consistency, FLC has a simple control structure and more flexiable control rules.
A dynamic mathematical model of a three-effect falling film evaporator is developed by using MATLAB based on the mass and energy balance principles in this thesis for analysing the optimization and controllability of the plant. Both conventional and advanced controllers, such as conventional PID, auto-tuning PID, Model predictive control (MPC), Fuzzy logic, are described to maintain and improve the mathematical model performances.
The product output concentration controlled by different strategies are obtained and compared. The results indicate that all controllers can achieve the desired targets (30%, 38% and 52% for the 1st, 2nd, and 3rd effect) within limits of acceptability, however, MPC is the most competitive advanced control strategy in this milk evaporation process
Dynamical Modeling and Control of Multiphase Heat Transport Systems Based on Loop Heat Pipes
Effective heat transport systems in aerospace are based on multiphase loop heat pipes (LHPs). For a precise thermal control of the electronics, electrical heaters are additionally used to control the operating temperature of the LHP. This work focusses on the dynamical modeling and model-based control design for LHP-based heat transport systems. The results of this work can be used for the optimization of current control parameters and the efficient control design for future LHP applications
Dynamical Modeling and Control of Multiphase Heat Transport Systems Based on Loop Heat Pipes
Effective heat transport systems in aerospace are based on multiphase loop heat pipes (LHPs). For a precise thermal control of the electronics, electrical heaters are additionally used to control the operating temperature of the LHP. This work focusses on the dynamical modeling and model-based control design for LHP-based heat transport systems. The results of this work can be used for the optimization of current control parameters and the efficient control design for future LHP applications
Design, construction and commissioning of the Thermal Screen Control System for the CMS Tracker detector at CERN
The CERN (European Organization for Nuclear Research) laboratory is currently building the Large Hadron Collider (LHC). Four international collaborations have designed (and are now constructing) detectors able to exploit the physics potential of this collider. Among them is the Compact Muon Solenoid (CMS), a general purpose detector optimized for the search of Higgs boson and for physics beyond the Standard Model of fundamental interactions between elementary particles. This thesis presents, in particular, the design, construction, commissioning and test of the control system for a screen that provides a thermal separation between the Tracker and ECAL (Electromagnetic CALorimeter) detector of CMS (Compact Muon Solenoid experiment). Chapter 1 introduces the new challenges posed by these installations and deals, more in detail, with the Tracker detector of CMS. The size of current experiments for high energy physics is comparable to that of a small industrial plant: therefore, the techniques used for controls and regulations, although highly customized, must adopt Commercial Off The Shelf (COTS) hardare and software. The âワslow controlâ systems for the experiments at CERN make extensive use of PLCs (Programmable Logic Controllers) and SCADA (Supervisory Control and Data Acquisition) to provide safety levels (namely interlocks), regulations, remote control of high and low voltages distributions, as well as archiving and trending facilities. The system described in this thesis must follow the same philosophy and, at the same time, comply with international engineering standards. While the interlocks applications belong straightforwardly to the category of DES (Discrete Event System), and are therefore treated with a Finite State Machine approach, other controls are more strictly related to the regulation problem. Chapter 2 will focus on various aspects of modern process control and on the tools used to design the control system for the thermal screen: the principles upon which the controller is designed and tuned, and the model validated, including the Multiple Input-Multiple Output (MIMO) problematics are explained. The thermal screen itself, the constraints and the basis of its functioning are described in Chapter 3, where the thermodynamical design is discussed as well. For the LHC experiments, the aim of a control system is also to provide a well defined SIL (Safety Interlock Level) to keep the system in a safe condition; yet, in this case, it is necessary to regulate the temperature of the system within certain values and respect the constraints arising from the specific needs of the above mentioned subsystems. The most natural choice for a PLC-based controller is a PID (Proportional Integral Derivative) controller. This kind of controller is widely used in many industrial process, from batch production in the pharmaceutics or automotive field to chemical plants, distillation columns and, in general, wherever a reliable and robust control is needed. In order to design and tune PID controllers, many techniques are in use; the approach followed in this thesis is that of black-box modeling: the system is modeled in the time domain, a transfer function is inferred and a controller is designed. Then, a system identification procedure allows for a more thorough study and validation of the model, and for the controller tuning. Project of the thermal screen control including system modeling, controller design and MIMO implementation issues are entirely covered in Chapter 4. A systems engineering methodology has been followed all along to adequately manage and document every phase of the project, complying with time and budget constraints. A risk analysis has been performed, using Layer of Protection Analysis (LOPA) and Hazard and Operability Studies (HAZOP), to understand the level of protection assured by the thermal screen and its control components. Tests planned and then performed to validate the model and for quality assurance purposes are described in Chapter 5. A climatic chamber has been designed and built at CERN, where the real operating conditions of the thermal screen are simulated. Detailed test procedures have been defined, following IEEE standards, in order to completely check every single thermal screen panel. This installation allows for a comparison of different controller tuning approaches, including IAE minimization, Skogestad tuning rules, Internal Model Control (IMC), and a technique based upon the MatLab Optimization toolbox. This installation is also used for system identification purposes and for the acceptance tests of every thermal screen panel (allowing for both electrical and hydraulic checks). Also, tests have been performed on the West Hall CERN experimental area , where a full control system has been set up, for interlock high- and low- voltage lines. The interlock system operating procedures and behaviour have been validated during real operating conditions of the detector esposed to a particle beam. The satisfactory results of tests take the project to full completion, allowing the plan to reach the âワexitâ stage, when the thermal screen is ready to be installed in the Tracker and ready to be operational
Dynamical Modeling and Control of Multiphase Heat Transport Systems Based on Loop Heat Pipes
Effective heat transport systems in aerospace are based on multiphase loop heat pipes (LHPs). For a precise thermal control of the electronics, electrical heaters are additionally used to control the operating temperature of the LHP. This work focusses on the dynamical modeling and model-based control design for LHP-based heat transport systems. The results of this work can be used for the optimization of current control parameters and the efficient control design for future LHP applications
Applications of Mathematical Models in Engineering
The most influential research topic in the twenty-first century seems to be mathematics, as it generates innovation in a wide range of research fields. It supports all engineering fields, but also areas such as medicine, healthcare, business, etc. Therefore, the intention of this Special Issue is to deal with mathematical works related to engineering and multidisciplinary problems. Modern developments in theoretical and applied science have widely depended our knowledge of the derivatives and integrals of the fractional order appearing in engineering practices. Therefore, one goal of this Special Issue is to focus on recent achievements and future challenges in the theory and applications of fractional calculus in engineering sciences. The special issue included some original research articles that address significant issues and contribute towards the development of new concepts, methodologies, applications, trends and knowledge in mathematics. Potential topics include, but are not limited to, the following: Fractional mathematical models; Computational methods for the fractional PDEs in engineering; New mathematical approaches, innovations and challenges in biotechnologies and biomedicine; Applied mathematics; Engineering research based on advanced mathematical tools
Performance indicators for the dynamics modeling and control of PEMFC systems
Society is gradually becoming aware that the current energy industry, based on the
use of fossil fuels, is inefficient, highly polluting and has a finite supply. Within the
scientific community, there are indications that hydrogen (H2) as an energy vector,
obtained from renewable energy sources, can represent a viable option to mitigate
the problems associated with hydrocarbon combustion. In this context, the change
from the current energy industry to a new structure with a significant involvement of
H2 facilitates the introduction of fuel cells as elements of energy conversion. Polymer
Electrolyte Membrane Fuel Cells (PEMFC) are gaining increased attention as viable
energy conversion devices for a wide range of applications from automotive,
stationary to portable. In order to optimize performance, these systems require active
control and thus in-depth knowledge of the system dynamics which include fluid
mechanics, thermal dynamics and reaction kinetics. One of the main issues, with
respect to proper control of these systems, is the understanding of the water
transport mechanisms through the membrane and the liquid water distribution. The
thesis is based on the publication of nine international journal articles that are divided
into 4 sub-topics: Dynamic fuel cell modeling, fuel cell system control-oriented
analysis, identification of parameters and performance indicators and finally, fault
and failure detection and system diagnosis. In the sub-topic of Dynamic Fuel cell
modeling, experimentally validated Computational Fluid Dynamics (CFD) modeling is
used to relate the effects of the physical phenomena associated with fluid mechanics
and thermal dynamics, that occur inside the fuel cell [Alonso, 2009][Strahl, 2011], to
water distribution. However, since these CFD models cannot be directly used for
control, control-oriented models [Kunusch, 2008][Kunusch, 2011] have been
developed in parallel. As well, another study is done in [Serra, 2006] which includes
a controllability analysis of the system for future development and application of
efficient controllers. The results of the above mentioned studies are limited because
either they do not incorporate an electrochemical model or the model is not experimentally validated. Moreover, these models do not take into account the
voltage losses due to liquid water inside the fuel cell. Therefore, there is a need to
properly relate the relevant effects of fluid mechanics and thermal dynamics,
including liquid water, to the fuel cell voltage. Primarily, methodologies are needed to
determine the relevant indicators associated to the effect of water on the fuel cell
performance. The works published in [Husar, 2008] and [Husar, 2011] treats
experimental parameter identification, mainly focused on water transport through the
membrane and fuel cell voltage loss indicators respectively. The implementation of
the indicators indirect measurement methodology provides an experimental way for
the isolation of three main types of voltage losses in the fuel cell: activation, mass
transport and ohmic losses. Additionally since these voltage loss indicators relate the
fuel cell operating conditions to the fuel cell voltage, they can be utilized to calibrate
and validate CFD models as well as employed in novel control strategies. On the
other hand, to develop reliable systems, the controller should not only take into
account performance variables during standard operation but should also be able to
detect failures and take the appropriate actions. A preliminary study on failure
indicators is presented in [Husar 2007] and fault detection methodologies are
described in [de Lira 2011]. As a whole, the compilation of articles represented in this
thesis applies a comprehensive experimental approach which describes the
implementation of novel methodologies and experimental procedures to characterize
and model the PEMFC and their associated systems taking into consideration
control oriented goals.La societat s'està adonant que la indústria energètica actual, basada en l'ús de
combustibles fòssils, és ineficient, molt contaminant i té un subministrament limitat.
Dins de la comunitat científica, hi ha indicis que el hidrogen (H2) com vector
energètic, obtingut a partir de fonts d'energia renovables, pot representar una opció
viable per a mitigar els problemes associats amb la combustió d'hidrocarburs. En
aquest context, el canvi de la indústria energètica actual a una nova estructura amb
una important participació de el hidrogen exigeix la introducció de les piles de
combustible com elements de conversió d'energia. Les piles de combustible de
membrana polimèrica (PEMFC) estan tenint cada vegada més atenció com a
dispositius viables de conversió d'energia per a una àmplia gamma d'aplicacions
com automoció, estacionàries o portàtils. Amb la finalitat d'optimitzar el seu
rendiment, les piles PEM requereixen un control actiu i per tant un coneixement
profund de la dinàmica del sistema, que inclou la mecànica de fluids, la dinàmica
tèrmica i la cinètica de les reaccions. Un dels temes principals relacionat amb el
control adequat d'aquests sistemes és la comprensió dels mecanismes de transport
d'aigua a través de la membrana i la distribució d'aigua líquida. Aquesta tesi es basa
en nou articles publicats en revistes internacionals que es divideixen en 4 subtemes:
la modelització dinàmica de piles de combustible, l'anàlisi orientada al control
del sistema, la identificació de paràmetres i d’indicadors de funcionament i,
finalment, la detecció de fallades i la diagnosi dels sistemes. En el sub-tema de la
modelització dinàmica de piles PEM, la modelització basada en la Dinàmica de
Fluids Computacional (CFD) amb validació experimental s'ha utilitzat per a
relacionar els efectes dels fenòmens físics de la mecànica de fluids i de la dinàmica
tèrmica que es produeixen dintre de la pila [Alonso, 2009] [ Strahl, 2011] amb la
distribució d'aigua. No obstant això, com aquests models CFD no poden ser utilitzats
directament per al control, s'han desenvolupat models orientats a control [Kunusch,
2008] [Kunusch, 2011] en paral·lel. A més, en un altre estudi [Serra, 2006] s'inclou una anàlisi de control·labilitat del sistema per al desenvolupament i aplicació futurs
de controladors eficaços. Però els resultats dels estudis esmentats anteriorment són
limitats, ja sigui perquè no incorporen un model electroquímic o bé perquè no han
estat validats experimentalment. A més, cap dels models té en compte les pèrdues
de tensió degudes a l'aigua líquida dins de la pila de combustible. Per tant, hi ha una
necessitat de relacionar adequadament els efectes rellevants de la mecànica de
fluids i de la dinàmica tèrmica, incloent l'aigua líquida, amb el voltatge de la pila de
combustible. Principalment, són necessàries metodologies per a determinar els
indicadors rellevants associats a aquest efecte de l'aigua sobre el rendiment de la
pila de combustible. Els treballs publicats en [Husar, 2008] i [Husar, 2011] tracten la
identificació experimental de paràmetres, centrada en el transport d'aigua a través
de la membrana i els indicadors de pèrdua de tensió, respectivament. L'aplicació
d'una proposta de metodologia de mesura indirecte dels indicadors permet
l'aïllament dels tres tipus principals de pèrdues de voltatge en la pila de combustible:
l'activació, el transport de massa i les pèrdues ohmiques. Aquests indicadors de
pèrdua de tensió relacionen les condicions d'operació amb el voltatge de la pila de
combustible i per tant poden ser utilitzats per a calibrar i validar models CFD, així
com per a definir noves estratègies de control. D'altra banda, per a aconseguir
sistemes fiables, el controlador no només ha de considerar els indicadors de
funcionament de l'operació normal, sinó que també ha de detectar possibles fallades
per a poder prendre les accions adequades en cas de fallada. Un estudi preliminar
sobre indicadors de fallades es presenta en [Husar 2007] i una metodologia de
detecció de fallades completa es descriu en [Lira de 2011]. En el seu conjunt, el
compendi d'articles que formen aquesta tesi segueix un enfocament experimental i
descriu la implementació de noves metodologies i procediments experimentals per a
la caracterització i el modelatge de piles PEM i els sistemes associats amb objectius
orientats al control eficient d'aquests sistemes.La sociedad se ésta dando cuenta de que la industria energética actual, basada en
el uso de combustibles fósiles, es ineficiente, muy contaminante y tiene un
suministro limitado. Dentro de la comunidad científica, hay indicios de que el
hidrógeno (H2) como vector energético, obtenido a partir de fuentes de energía
renovables, puede representar una opción viable para mitigar los problemas
asociados con la combustión de hidrocarburos. En este contexto, el cambio de la
industria energética actual a una nueva estructura con una importante participación
de H2 exige la introducción de pilas de combustible como elementos de conversión
de energía. Las pilas de combustible de membrana polimérica (PEMFC) están
ganando cada vez más atención como dispositivos viables de conversión de energía
para una amplia gama de aplicaciones como automoción, estacionarias o portátiles.
Con el fin de optimizar su rendimiento, las pilas PEM requieren un control activo y
por lo tanto un conocimiento profundo de la dinámica del sistema, que incluye la
mecánica de fluidos, la dinámica térmica y la cinética de las reacciones. Uno de los
temas principales relacionado con el control adecuado de estos sistemas, es la
comprensión de los mecanismos de transporte de agua a través de la membrana y
la distribución de agua líquida. Esta tesis se basa en la publicación de nueve
artículos en revistas internacionales que se dividen en 4 sub-temas: el modelado
dinámico de pilas de combustible, el análisis orientado a control del sistema, la
identificación de parámetros e indicadores de desempeño y, por último, la detección
de fallos y la diagnosis. En el sub-tema de la modelización dinámica de pilas PEM,
el modelado basado en Dinámica de Fluidos Computacional (CFD) con validación
experimental se ha utilizado para relacionar los efectos de los fenómenos físicos de
la mecánica de fluidos y la dinámica térmica que se producen dentro de la pila
[Alonso, 2009] [ Strahl, 2011] con la distribución de agua. Sin embargo, como estos modelos CFD no pueden ser utilizados directamente para el control, modelos
orientados a control [Kunusch, 2008] [Kunusch, 2011] se han desarrollado en
paralelo. Además, en otro estudio [Serra, 2006] se incluye un análisis de
controlabilidad del sistema para el futuro desarrollo y aplicación de controladores
eficaces. Pero los resultados de los estudios mencionados anteriormente son
limitados, ya sea porque no incorporan un modelo electroquímico o bien porque no
son validados experimentalmente. Además, ninguno de los modelos tiene en cuenta
las pérdidas de tensión debidas al agua líquida dentro de la pila de combustible. Por
lo tanto, hay una necesidad de relacionar adecuadamente los efectos relevantes de
la mecánica de fluidos y la dinámica térmica, incluyendo el agua líquida, con la
tensión de la pila de combustible. Principalmente, son necesarias metodologías para
determinar los indicadores relevantes asociados al efecto del agua sobre el
rendimiento de la pila de combustible. Los trabajos publicados en [Husar, 2008] y
[Husar, 2011] tratan la identificación experimental de parámetros, centrada en el
transporte de agua a través de la membrana y los indicadores de pérdida de tensió,
respectivamente. La aplicación de una metodología propuesta de medición indirecta
de los indicadores permite el aislamiento de los tres tipos principales de pérdidas de
tensión en la pila de combustible: la activación, el transporte de masa y las pérdidas
óhmicas. Éstos indicadores de pérdida de tensión relacionan las condiciones de
operación con la tensión de la pila de combustible y por lo tanto pueden ser
utilizados para calibrar y validar modelos CFD, así como para definir nuevas
estrategias de control. Por otro lado, para conseguir sistemas fiables, el controlador
no sólo debe considerar los indicadores de desempeño de la operación regular, sino
que también debe detectar posibles fallos para poder tomar las acciones adecuadas
en caso de fallo. Un estudio preliminar sobre indicadores de fallos se presenta en
[Husar 2007] y una metodología de detección de fallos completa se describe en [Lira
de 2011]. En su conjunto, el compendio de artículos que forman esta tesis sigue un
enfoque experimental y describe la implementación de nuevas metodologías y
procedimientos experimentales para la caracterización y el modelado de pilas PEM
y los sistemas asociados con objetivos orientados al control eficiente de estos
sistemas
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