@phdthesis{Ritschel2006, author = {Ritschel, J{\"u}rgen}, title = {Belastung der B{\"o}den des Landes Brandenburg mit PAK und PCB : Akkumulationsf{\"a}higkeit und Transferverm{\"o}gen}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-272}, school = {BTU Cottbus - Senftenberg}, year = {2006}, abstract = {Im Rahmen der Arbeit werden nutzungs- und standortspezifische Hintergrundwerte f{\"u}r organische Schadstoffe (PAK, BaP und PCB) in Brandenburger Oberb{\"o}den abgeleitet. Dabei wird der Medianwert im Sinne eines Hintergrundwertes, der den Normalzustand beschreibt, verwendet. Das 90er Perzentil charakterisiert eine den Normalzustand {\"u}berschreitende Schadstoffkonzentration und fungiert als Referenzwert. Um den Transfer von PAK und PCB vom Boden in die Pflanze zu ermitteln, wurden Gef{\"a}ßversuche mit f{\"u}r Brandenburg typischen B{\"o}den und Kulturen sowie Erhebungsuntersuchungen auf landwirtschaftlichen Fl{\"a}chen ausgewertet. Gepr{\"u}ft wurde der Schadstofftransfer in die Fruchtarten Mais, Kartoffel, M{\"o}hre, Salat, Spinat, Gras und Weizen. Festzustellen war, dass sich der PAK- und PCBTransfer in die Pflanze unter den Bedingungen der relativ leichten und schlecht mit organischer Substanz versorgten B{\"o}den des Landes Brandenburg auf niedrigem Niveau bewegt.}, subject = {Brandenburg; Bodenverschmutzung; Polycyclische Aromaten; Polychlorierte Biphenyle; Hintergrundwert; Oberboden; Polycyclische Aromatische Kohlenwasserstoffe; Polychlorierte Biphenyle; Referenzwert; Background value; Topsoil; Polycyclic aromatic hydrocarbons; Polychlorinated biphenyl; Reference value}, language = {de} } @phdthesis{FeiBaffoe2006, author = {Fei-Baffoe, Bernard}, title = {Double stage dry-wet fermentation of unsorted municipal solid waste}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-245}, school = {BTU Cottbus - Senftenberg}, year = {2006}, abstract = {Aim of the study In this thesis, the recovery of biogas from Unsorted Municipal Solid Waste with high methane content was investigated. Special attention was given to unsorted municipal solid waste since its management is posing a big challenge for solid waste management authorities especially in developing countries (e.g. Accra, Ghana). Common solid waste management practice in most of the communities involves having the entire components of the waste mixed together and deposited in bins or on a bare ground at locations within communities and subsequently hauled to the dumpsite by the waste authority. In a laboratory study, a simulated waste was developed representing the real waste situation in Accra, Ghana to leach out the biodegradable organic fraction and subsequent biogas recovery. Method of investigation In order to optimize the biodegradation of Unsorted Municipal Solid Waste, the double-stage anaerobic digester with optimum design capability and with both intra and inter liquid recirculation, and microaerophilic hydrolysis conditions was employed. In order to biomethanize the waste, the following hypotheses were tested: · Effect of water flow rate (dilutions) on the extent of hydrolysis/ liquefaction. · Solid retention time and biodegradation. · Temperature on the extent of hydrolysis. · Effect of preprocessed feeding material on hydrolysis and gas yield. Results and technical applicability The results indicate that the various conditions tested are effective in determining the biogas production from the Unsorted Municipal Solid Waste. Following several runs for the optimization process, volume and mass reduction of 30±19\% and 42±13\% was achieved respectively. Importantly, almost 42\% of the organic total solids reduction with equivalent of methane yield of 232±66 l CH4/kg OTS was obtained. A concept is developed for the application of the double-stage digester for the biomethanization of Unsorted Municipal Solid Waste. This concept involves the appropriate optimum conditions required for the biodegradation process. Finally the potential of using Unsorted Municipal Solid Waste for commercial biogas production was emphasized.}, subject = {Siedlungsabfall; Fermentation; Biogasgewinning; Siedlungsabf{\"a}lle; Abfallentsorgung; Biogasproduktion; Unsorted municipal solid waste; Double-stage digester; Fermentation; Biogas}, language = {en} } @phdthesis{Krueger2006, author = {Kr{\"u}ger, Thomas}, title = {Beitrag zum systematischen Steuerungsentwurf von Mehrmotorenantriebssystemen am Beispiel eines Laborversuchsstandes mit fahrzeugspezifischen Eigenschaften}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-233}, school = {BTU Cottbus - Senftenberg}, year = {2006}, abstract = {Durch den Einsatz eines elektrischen Mehrmotorenantriebs k{\"o}nnen mechanische Komponenten, wie Getriebe und Differential, durch eine {\"u}bergeordnete Steuerung ersetzt werden. In dieser Arbeit werden die Grundlagen zur Untersuchung eines solchen Fahrzeugantriebs an einem Laborversuchsstand geschaffen. Durch eine speziell ausgelegte {\"u}bergeordnete Steuerung wird die experimentelle Untersuchung verschiedener Algorithmen f{\"u}r Fahrsicherheitssysteme und deren Funktion erm{\"o}glicht. Zum Einsatz kommen Axialflussmaschinen deren Bauform einen Einsatz als Radnabenmotor erlauben. Durch eine Anordnung von Belastungsmaschinen an der Antriebsachse erfolgt die Vorgabe realit{\"a}tsnaher Belastungszust{\"a}nde und -profile. Vorteil gegen{\"u}ber einem direkten Einbau und Funktionstest in einem Kraftfahrzeug ist die M{\"o}glichkeit das Fahrverhalten auch in kritischen Fahrsituationen untersuchen zu k{\"o}nnen. Das ganze ist ohne Gef{\"a}hrdung der Umgebung kosteng{\"u}nstig m{\"o}glich.}, subject = {Mehrmotorenantrieb; Steuerung; Fahrzeugantrieb; Elektroantrieb; Mehrmotorenantrieb; Antriebssteuerung; Vehicle drive; Electrical motor; Multi-engined-drive; Drive control}, language = {de} } @phdthesis{Jurk2005, author = {Jurk, Steffen}, title = {A Simultaneous Execution Scheme for Database Caching}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-228}, school = {BTU Cottbus - Senftenberg}, year = {2005}, abstract = {Database caching techniques promise to improve the performance and scalability of client-server database applications. The task of a cache is to accept requests of clients and to compute them locally on behalf of the server. The content of a cache is filled dynamically based on the application and users' data domain of interest. If data is missing or concurrent access has to be controlled, the computation of the request is completed at the central server. As a result, applications benefit from quick responses of a cache and load is taken from the server. The dynamic nature of a cache, the need of transactional consistency, and the complex nature of a request make database caching a challenging field of research. This thesis presents a novel approach to the shared and parallel execution of stored procedure code between a cache and the server. Every commercial database product provides such stored procedures that are coded in a complete programming language. Given a request in form of such a procedure, we introduce the concept of split twin transactions that logically split the procedure code into two parts, say A and B, such that A is executed at the cache and B at the server in a simultaneous and parallel manner. Furthermore, we analyse the procedure code to detect suitable parts. To the best of our knowledge, this has not yet been addressed by any existing approaches. Within a detailed case study, we show that our novel scheme improves the performance of existing caching approaches. Furthermore, we demonstrate that different load conditions of the system require different sizes of the parts A and B to gain maximal performance. As a result, we extend database caching by a new dimension of optimization, namely by splitting of the procedure code into A and B. To solve this problem of dynamically balancing the code execution between cache and server, we define the maximum performance of a database cache over time and propose a stochastic model to capture the average execution time of a procedure. Based on the execution frequencies of primitive database operations, the model allows us to partially predict the response times for different sizes of A and B, hence providing a partial solution to the optimization problem.}, subject = {Datenbankentwurf; Zugriff; Simultaneous Engineering; Datenbank-Cache-Technik; Datenbankoptimierung; Zwillingstransaktion; Database caching; Database optimization; Twin transactions; Simultaneous execution; Stored procedures}, language = {en} } @phdthesis{SanchezSanchez2006, author = {S{\´a}nchez S{\´a}nchez, David}, title = {Key management for wireless ad hoc networks}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-164}, school = {BTU Cottbus - Senftenberg}, year = {2006}, abstract = {Key management is a fundamental security service to enable secure wireless ad hoc networks (WAHN). To date existing key management solutions based on either public key infrastructures (PKI) or key pre‑distribution scheme (KPS) exhibit limitations for WAHNs. We firstly develop the Hybrid Key Management Infrastructure (HKMI) for WAHNs composed of moderate‑resource devices. The HKMI complements PKI with trust and cooperation protocols to construct an performance efficient security solution. We secondly develop the Deterministic Pairwise Key Pre-Distribution Scheme (DPKPS) for large‑scale dynamic WAHNs composed of low‑resource devices. The DPKPS applies a combinatorial design for the pre-distribution of multiple bivariate polynomial shares to WAHN nodes. Future work comprises further improving the resiliency of the DPKPS, completing a key management infrastructure on the basis of the DPKPS, the design of DPKPS‑based access control mechanisms, and the integration of the HKMI with the DPKPS in a unified key management architecture.}, subject = {Ad-hoc-Netz; Verteiltes System; Key management; Sicherheit; Schl{\"u}sselmanagement; Ad-hoc-Netz; Security; Key management; Ad hoc networks}, language = {en} } @phdthesis{Wagenschein2006, author = {Wagenschein, Dierk}, title = {Einfluß der Gew{\"a}ssermorphologie auf die N{\"a}hrstoffretention : Modellstudie am Beispiel der mittleren Weißen Elster}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-216}, school = {BTU Cottbus - Senftenberg}, year = {2006}, abstract = {Hohe N{\"a}hrstoffkonzentrationen k{\"o}nnen aquatische {\"O}kosysteme stark belasten. Bei der integrierten Gew{\"a}sserbewirtschaftung kommt der Quantifizierung der nat{\"u}rlichen N{\"a}hrstoffsenken eine große Bedeutung zu. F{\"u}r den anorganischen Stickstoff sind dies die biogene Assimilation und die benthische Denitrifikation. Denitrifikation wurde bisher vor allem auf der Prozessskala untersucht, eine r{\"a}umlich differenzierte Erfassung auf mesoskaliger Ebene ist noch nicht erfolgt. Hauptziel dieser Arbeit ist die r{\"a}umlich aufgel{\"o}ste Quantifizierung des N{\"a}hrstoffumsatzes - mit besonderer Ber{\"u}cksichtigung der Stickstoffretention - am Beispiel eines 70 km langen Flussabschnitts der Weißen Elster. Dies wird anhand von L{\"a}ngsschnitt- und Tag/Nacht-Beprobungen, bei denen auch der benthische Biofilm und die Sedimente ber{\"u}cksichtigt wurden, analysiert. Der Schwerpunkt der Arbeit liegt auf der Durchf{\"u}hrung von Modellanalysen. Es wurde eine modifizierte Version des Gew{\"a}sserg{\"u}temodells WASP verwendet. Damit wurden die Sensitivit{\"a}ten morphologischer Faktoren untersucht sowie die Einfluss von Renaturierungsmaßnahmen auf den N{\"a}hrstoffhaushalt analysiert. Unter sommerlichen Verh{\"a}ltnissen wurde eine erhebliche Stickstoffretention nachge­wiesen. Auf der 70 km langen Fließstrecke werden bis zu 32\% der in das Gew{\"a}sser eingetragenen N-Fracht durch Denitrifikation eliminiert. Die Denitrifikation schwankt r{\"a}umlich sehr stark: Der Stickstoffr{\"u}ckhalt liegt zwischen 0,2 und 1,25 mgN/(l·d), die mittlere Denitrifikationsrate schwankt zwischen 240 mgN/(m2d) in einem kanalisierten Abschnitt und 639 mgN/(m2d) in einem naturnahen Bereich. Von den untersuchten morphologischen Faktoren hat die L{\"a}nge der Fließstrecke den gr{\"o}ßten Einfluss auf den Stickstoffr{\"u}ckhalt. Eine Verl{\"a}ngerung der Fließstrecke um 10\% bewirkt eine Verringerung der Nitrat-Konzentration um 2,7\%. Die Auswirkungen der im Rahmen einer Szenarienanalyse betrachteten Renaturierungs­maßnahmen auf die Stickstoffbelastung sind gering.}, subject = {Weiße Elster; N{\"a}hrstoffretention; Geomorphologie; Fließgew{\"a}sser; N{\"a}hrstoffretention; Morphologie; Gew{\"a}sserg{\"u}temodellierung; River morphology; Nitrogen retention; River water quality modelling; Model identification}, language = {de} } @phdthesis{Vasylyev2006, author = {Vasylyev, Andriy}, title = {Integrated RF power amplifier design in Silicon-based technologies}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-202}, school = {BTU Cottbus - Senftenberg}, year = {2006}, abstract = {This thesis presents the design and implementation of the RF power amplifiers in modern silicon based technologies. The main challenge is to include power amplifier on a single chip with output power level in watts, operating at high frequencies where the transit frequency (fT) is just a few times higher than the operating frequency. This work describes the design procedure for bipolar and CMOS transformer-based Class-A, Class-AB and Class-B power amplifiers. The design procedure is based on the HICUM for bipolar and BSIM4 for CMOS transistor models and is divided in four parts: •Building a one transistor prototype power amplifier which is based on the analytical analysis of the output characteristics and transistor model. •Load-pull simulation to define the final input and output impedances. •Derivation of the analytical equations for the transformer-based matching network. •Design of the final transformer-based push-pull power amplifier. A good agreement between the proposed analytical analysis and large-signal (harmonic balance) simulation results proofs usefulness of the proposed power amplifier design approach. Additionally, it shows the contribution of the separated devices at the final design that helps to find a technology limits in the current circuit design. The main achievements include: •A 2.4 GHz power amplifier in 0.13 um CMOS technology. An output power of 28 dBm is achieved with a power added efficiency of 48 \% at a supply voltage of 1.2 V [Vasylyev 04]. •Two 17 GHz power amplifiers in 0.13 um CMOS technology (one fully integrated while the other with external matching network) with output power exceeding 50 mW. The former exhibits a power added efficiency of 9.3 \% while the latter a 15.6 \% power added efficiency [Vasylyev 06]. •A fully integrated K and Ka bands power amplifier in 0.13 um CMOS technology. A 13 dBm output power along with power added efficiency of 13 \% is achieved at an operating frequency of 25.7 GHz with 1.2 V supply [Vasylyev 05,a]. •A fully integrated power amplifier based on a novel power combining transformer structure in 28 GHz-fT SiGe-bipolar technology. A 32 dBm output power along with power added efficiency of 30 \% is achieved at an operating frequency of 2.12 GHz with 3.5 V supply [Vasylyev 05,b].}, subject = {Siliciumbauelement; Radiofrequenzbereich; Verst{\"a}rker; Leistungsverst{\"a}rker; CMOS; Power amplifier; CMOS}, language = {en} } @phdthesis{Pritzkow2006, author = {Pritzkow, Olaf}, title = {Untersuchungen zum Um- und Durchstr{\"o}mungsverhalten von einzelnen Agglomeratstrukturen}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-187}, school = {BTU Cottbus - Senftenberg}, year = {2006}, abstract = {In dieser Arbeit werden Untersuchungen von Agglomeratstrukturen in verschiedenen Geschwindigkeitsbereichen hinsichtlich ihres Widerstandsverhaltens in Str{\"o}mungen pr{\"a}sentiert. Daraus ableitend wird ein Porenmodell f{\"u}r offene Agglomeratstrukturen vorgeschlagen, das auf dem Hinzuf{\"u}gen von durchgehenden geraden {\"O}ffnungen entsprechender Gr{\"o}ßenordnung in Vollkugeln basiert. Die Wahl des Porensystems ist dabei an bekannte geometrische und strukturelle Eigenschaften der Agglomerate angelehnt. Die physikalisch begr{\"u}ndete Vorstellung der Wirkung von Druck- und Reibungskr{\"a}ften unter verschiedenen Relativgeschwindigkeiten wird qualitativ best{\"a}tigt und ein quantitativer Bezug zur Oberfl{\"a}che und anderen geometrischen Gr{\"o}ßen hergestellt. Des Weiteren werden Weiterentwicklungen der Messmethoden sowohl bei der Sedimentation als auch bei der mechanischen Fixierung beschrieben. Abschließend werden die elektrotechnischen Grundlagen f{\"u}r eine ber{\"u}hrungslose Magnetfeldmessmethode angegeben.}, subject = {Agglomerat; Umstr{\"o}mung; Durchstr{\"o}mung; Fluid-Feststoff-System; Agglomerate; Str{\"o}mungsverhalten; Magnetfeldfixierung; Reynolds-Zahl; Fraktal; Agglomerate; Flow behavior; Magnetic field fixation; Reynolds number; Fractal}, language = {de} } @phdthesis{Tavakoli2006, author = {Tavakoli, Mohammad Hossein}, title = {Numerical analysis of seeding process during Czochralski growth of oxide single crystals}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-145}, school = {BTU Cottbus - Senftenberg}, year = {2006}, abstract = {A series of two-dimensional and three-dimensional quasi-steady state numerical simulations have been performed for the initial stages (seeding process) of the Czochralski (CZ) growth of oxide crystals using the finite element method (FEM). We have considered different cases and configurations with respect to real systems in the CZ-dielectrics laboratory of the Institute for Crystal Growth (IKZ). Using induction heating in metallic parts as heat source the fluid flow and temperature field were determined in the whole CZ system. The aim of these calculations was to investigate and reveal the effect of several parameters such as the geometry and location of an active afterheater with respect to the crucible, arrangement and design of thermal insulation, crucible bottom shape, and seed rotation rate on the flow and temperature field of the system and the seed-melt interface shape. The results demonstrate that the temperature and fluid flow in the gas domain is strongly affected by an active afterheater and its insulation as well as their geometry and position. The results also show the important role played by the seed rotation rate for influencing the shape of the seed-melt interface.}, subject = {Kristallz{\"u}chtung; Czochralski-Verfahren; Czochralski-Verfahren; Ankeimprozess; Temperaturverteilung; Kristallz{\"u}chtung; Czochralski method; Seeding process; Heat transfer; Induction heating}, language = {en} } @phdthesis{Ahlinder2006, author = {Ahlinder, Stefan}, title = {On modelling of compact tube bundle heat exchangers as porous media for recuperated gas turbine engine applications}, isbn = {3-8322-5355-6}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-151}, school = {BTU Cottbus - Senftenberg}, year = {2006}, abstract = {A computational tool and a methodology for steady state heat exchanger simulations of recuperated gas turbines and aero-engines have been developed. As an example a compact tube bundle heat exchanger with oval shaped tubes was chosen. The simulation tool proved to work for different layouts of the heat exchanger and for different geometrical configurations of the gas turbine engine exhaust ducts. The resistance tensors were tuned against both CFD-data and experimental data and the computational model was to some extent validated against experimental results. For the validation isothermal experimental data from the Laboratory of Fluid Mechanics and Turbomachinery at the Technical University of Thessaloniki was used together with hot gas channel data from MTU. The calculated and measured velocity profiles showed an acceptable agreement that in some of the cases was even very good. The calculated pressure drop deviated less than 10\% for the compared cases, which must be considered to be acceptable. The calculared results for the hot gas cases showed an exaggerated heat transfer rate, most likely due to the use of a cold side heat transfer correlation for fully turbulent flow, although the Reynolds numbersindicated transitional flow.}, subject = {Fluggasturbine; W{\"a}rmeaustauscher; Simulation; W{\"a}rmetauscher; CFD; Por{\"o}ses Medium; Rohrb{\"u}ndel; Heat exchanger; CFD; Porous medium; Tube bundle}, language = {en} }