Bøger udgivet af Cuvillier

Guideposts and traffic signals are important devices for controlling inner-city traffic and their optimized operation is essential for efficient traffic flow without congestion. In this thesis, we develop a mathematical model for guideposts and traffic signals in the context of network flow theory. Guideposts lead to confluent flows where each node in the network may have at most one outgoing flow-carrying arc. The complexity of finding maximum confluent flows is studied and several polynomial time algorithms for special graph classes are developed. For traffic signal optimization, a cyclically time-expanded model is suggested which provides the possibility of the simultaneous optimization of offsets and traffic assignment. Thus, the influence of offsets on travel times can be accounted directly. The potential of the presented approach is demonstrated by simulation of real-world instances.Vorwegweiser und Lichtsignalanlagen sind wichtige Elemente zur Steuerung innerstädtischen Verkehrs und ihre optimale Nutzung ist von entscheidender Bedeutung für einen staufreien Verkehrsfluss. In dieser Arbeit werden Vorwegweiser und Lichtsignalanlagen mittels der Netzwerkflusstheorie mathematisch modelliert. Vorwegweiser führen dabei zu konfluenten Flüssen, bei denen Fluss einen Knoten des Netzwerks nur gebündelt auf einer einzigen Kante verlassen darf. Diese konfluenten Flüsse werden hinsichtlich ihrer Komplexität untersucht und es werden Polynomialzeitalgorithmen für das Finden maximaler Flüsse auf ausgewählten Graphenklassen vorgestellt. Für die Versatzzeitoptimierung von Lichtsignalanlagen wird ein zyklisch zeitexpandiertes Modell entwickelt, das die gleichzeitige Optimierung der Verkehrsumlegung ermöglicht. So kann der Einfluss geänderter Versatzzeiten auf die Fahrzeiten direkt berücksichtigt werden. Die Leistungsfähigkeit dieses Ansatzes wird mit Hilfe von Simulationen realistischer Szenarien nachgewiesen.

This book presents theories and methods which enable a better comprehension of how powerful stakeholders influebce forest policy with community forestry as concrete example. Community forestry is being propagated all over the world by researchers, western bilateral organisations, NGOs and international institutions as a bottom-up model for community participation in forest and wildlife management especially in the tropical parts of the world. Academic and empirical publications analysing community participation in forest management have laid more emphasis on mainstream social and political theories and less on critical theories. Many publications highlight the importance of community forestry worldwide while at the same time question ist successes.The book will contribute to the scientific discourse while analyzing forest policy in Cameroon through the example of community forestry. Power being the core of the analysis as a driving factor fo forest policy in Cameroon, the book questions such as: (1) How an power be described in the context of forest policy, case study of community forestry? (2) What are the power processes? And (3) what outcomes of this power processes could be observed? The book analyzes the importance of power through political and critical theories, connecting them with other power theories and concepts formulated by the Community Forestry Working Group in Goettingen, Germany.

High-power, high-efficiency, wavelength-stabilized broad area (BA) diode lasers are promising devices for industrial applications. They can be used, for example, for pumping narrow absorption bands in gain media of solid-state and fiber lasers as well as for power scaling by means of dense spectral beam combining.This thesis focuses on the analysis and mitigation of the factors limiting the efficiency of high-power distributed feedback (DFB) diode lasers. In particular, it will be shown how a power conversion efficiency in the 60 %-range can be achieved from 10 W-class 100 ¿m stripe DFB-BA lasers ¿ values close to those of state-of-the-art Fabry-Pérot (FP) BA lasers. For the first time world-wide, newly developed DFB-BA lasers achieve 12 W continuous mode optical output power with 62 % peak power conversion efficiency and 58 % at 10 W, respectively. Wavelength stabilization is demonstrated from threshold to 15 A with a spectral width below 0.8 nm containing 95 % of the emitted power. The factors limiting the efficiency of DFB-BA lasers compared to state-of-the-art 10 W-class FP-BA lasers have been identified and as a result largely eliminated.

Im Rahmen dieser Arbeit wurden neue Modelle entwickelt, um Stickoxidemissionen und Klopfen in turboaufgeladenen Ottomotoren mit Direkteinspritzung abbilden zu können. Das Klopfmodell basiert auf einer Zündfortschrittsvariable für das Transportgleichungen für den Favre-Mittelwert und die ¿ Varianz hergeleitet worden sind. Die in diesen Gleichungen auftretenden mittleren chemischen Quellterme werden mittels einem ¿presumed PDF¿ Ansatz für Temperatur und Mischungsbruch in Kombination mit tabellierter detaillierter Reaktionskinetik bestimmt. Mit diesem Klopfmodell lässt sich an jedem Ort im Brennraum die Selbstzündungswahrscheinlichkeit bestimmen. Zur Bestimmung der Stickoxidemissionen wurde ein neues Multizonenmodell hergeleitet. Damit lassen sich die Zonen auf das verbranntes Gemisch konditionieren, um dort die Stickoxidbildung mittels detaillierter Reaktionskinetik zu berechnen. Durch den Abgleich mit experimentellen Ergebnisse konnte gezeigt werden, dass das Klopf- und NOx-Modell in der Lage sind den mittleren Klopfzeitpunkt und Anzahl klopfender Arbeitsspiele bzw. die Stickoxidemissionen mit hinreichender Genauigkeit zu bestimmen.

This thesis is concerned with mathematical optimization under data uncertainty using mixed integer linear programming (MILP) techniques. Our investigations follow the deterministic paradigm known as robust optimization. It allows to tackle an uncertain variant of a problem without increasing its complexity in theory or decreasing its computational tractability in practice.We consider four robustness concepts for robust optimization and describe their parametrization, application, and evaluation. The concepts are ¿-robustness, its generalization multi-band robustness, the more general submodular robustness, and the two-staged adaptive approach called recoverable robustness.For each concept, we investigate the corresponding robust generalization of the knapsack problem (KP), a fundamental combinatorial problem and subproblem of almost every integer linear programming (ILP) problem, and many other optimization problems. We present ILP formulations, detailed polyhedral investigations including new classes of valid inequalities, and algorithms for each robust KP. In particular, our results for the submodular and recoverable robust KP are novel. Additionally, the recoverable robust KP is experimentally evaluated in detail.Further, we consider the ¿-robust generalization of the capacitated network design problem (NDP). For example, the NDP arises from many application areas such as telecommunications, transportation, or logistics. We present MILP formulations, detailed polyhedral insights with new classes of valid inequalities, and algorithms for the ¿-robustness NDP. Moreover, we consider the multi-band robust NDP, its MILP formulations, and generalized polyhedral results of the ¿- robustness NDP.Finally, we present computational results for the ¿-robustness NDP using real-world measured uncertain data from telecommunication networks. These detailed representative studies are based on our work with the German ROBUKOM project in cooperation with Partner Nokia Siemens Networks GmbH & Co. KG.

Several studies have shown that educational attainment has reached a historicallyhigh level with nearly one in six rural adults holding a degree in a specific domainand three out of four have completed high school. However, in some developingcountries where emphasis has not been seriously placed on education for all, thenumber lags way behind. As the demand for food is increasing, people withagricultural knowledge are required to produce food to meet the growing demand.But the trend in agriculture has not been able to achieve this goal despite the levelof school completers in both developed and developing countries.To address this trend, this study assessed the status of school gardeninginstruction, compared and contrast students¿ and teachers¿ perceptions on schoolgardening projects and evaluated the level of teaching in the field of agriculture.This study evaluated factors influencing student and teacher interactions inregards to gardening and identifies the potential solutions that could be used topromote and increase the effectiveness of gardening projects. The potential rolesof parents, community members, government and state agencies in the furtherdevelopment of school gardening programs were also evaluated. The data wascollected from teachers and students in middle and high schools in Germany,Nigeria and U.S. The primary method of data collection involved the use ofquestionnaires which were distributed to 300 students and 33 teachers in the threecountries; 100 students and 11 teachers were selected from each country. Thedata were analyzed using quantitative methods. The results of this study identifiedteachers and school principals as the primary instruments of school gardeningsuccess. To increase the promotion, implementation and success of schoolgardening programs, principals and teachers should identify areas of need for theirparticular school related to gardening and make improvements to effect positivechanges. Also parents, community members, government and state agenciesshould express commitment to the school¿s role in order to set realistic objectivesfor successful school gardening project.

E-commerce offers opportunities for better competition by developing new products and markets, by bringing new actors onto the traditional markets and by developing new types of relationships between the traders. Additionally, using e-commerce, costs can be reduced and the satisfaction of the traders concerning faster delivery can be increased. Nevertheless, electronic transactions are not common in the agri-food sector compared with other businesses.Every B2B relationship and also e-commerce starts with a first transaction. The initial transaction only takes place when the buyer¿s perceived trustworthiness of the supplier exceeds the buyer¿s perceived risks of the transaction. However, the challenge of the first transaction in e-commerce is how to communicate trust without any previous experience. Trust helps enterprises to trade across border and profit from the online environment, especially in the agri-food sector which deals with complex products due to different uncertainties and risks regarding the food quality and safety.The main objective of this thesis is to analyse which elements of trust are essential in searching for a new international supplier and how these can be applied to e-commerce. To achieve this objective a stepwise approach has been developed by establishing the following phases: 1) identification of the most relevant trade flows; 2) exploration of trade relationships along the most relevant trade flows; 3) assessment of significance of traditional trust elements; 4) applications of traditional trust elements to e-commerce. The applications are determined by examining selected European (Germany, Austria, Italy, Greece, Spain and Slovenia) and cross-border (USA, Brazil and Turkey) agri-food chains (cereals, meat, fruits and vegetables, and olive oil) to contribute findings of possibly different cultural backgrounds. The identification of the most relevant trade flows (step one) is based on the statistical database and has been used as a basis for future research and to find out where the highest potential for the introduction of e-commerce in the international trade exists. The trade structures differed in the selected countries, and there is a complex picture.

Basically, the contemporary manipulation of identifiable living cells and bacteria in industrial andscientific processes has been functionally essentialized by the desire to improve on the state of thehuman condition in this modernizing era. Meanwhile, the prevalent globalizing culture has made itfeasible for quick exchange of information and, indeed, instant spread of cogent empirical knowledge.Such is the case with biotechnological development, which seeks to enhance agricultural productivity;health care delivery and, of course, the realization of the focal target of the ¿Millennium DevelopmentGoals¿ (MDGs), that is ¿halving extreme poverty by 2015¿. As noble as this innovation seemshowever, its application in Nigeria as obtainable in most parts of sub-Saharan Africa has been largelyuncoordinated, or at best, attenuated; ostensibly due to inactivity on the part of the political leadership.This study focuses on the explication of varying interpretations of the reality of biotechnologicalincorporation within Nigerian configuration. On the part of the policy planners, have usualproclamations been met with desired actions in the bid to localize such innovation in the country? Arethey conscious of its long-run human, social and environmental implications? On the other hand, arethe people ¿ the supposed direct beneficiaries of such adaptation aware of its existence andusefulness? How do they perceive and construct its reality? These and related issues are addressed inthis study. The methods of In-depth Interviews (IDIs) and Evaluation Research (ER) are engaged asthe study¿s modes of inquiry, while Berger and Luckmann¿s ¿The Social Construction of Reality¿ isadopted as its theoretical platform.

Rural households in Libya are credit constrained, in terms of access and the amount ofcredit received. Formal banks are the main players in credit market. Despite 44 branchesof agricultural banks distributed countrywide, these branches offer a limited number ofcredit for different purposes every year. The shares of these branches in rural creditmarket are quite small: agricultural banks provide only 24 % of loans and the otherbanks, mainly the commercial banks, provide 76 % of loans. However, agriculturalcredits provided by agricultural banks offer the most favorable terms for thosehouseholds that have a positive demand on agricultural credit. Households that have noaccess to agricultural credits on the other hand face the problem of paying a higherinterest rate when applying for credit from non-agricultural banks. This study is aninvestigation on ¿the importance of large credits in Libyan rural-areas, and the mainplayers in the rural-credit market¿. This study determines factors affecting access andcredit applications in three different locations. In addition, the affect of households, land,and socio-economic characteristics are analyzed using econometric analysis based onprimary data collected during field research in the years 2006 and 2007. Empiricalresults from the data collected from three different regions in Libya confirm that morethan half of rural households have no access to credit and around 42% of ruralhouseholds do not want to participate in loan borrowing or take loans from any financialinstitutions that charge high interest rate. This is mostly due to religious considerationsthat prohibit ¿unethical¿ interest rates charged by banks.

Understanding issues concerned with older workers and retirementis rapidly becoming a central concern within and beyond many disciplines.Economics, psychology, gerontology, sociology and educationhave provided insights in the many facets of this topic. Thecurrent debate and controversy reflects the shift from pushing awayolder workers from public life and employment towards retaining theiremployability, their knowledge and their wisdom.This publication provides a range of contributions which reflect theway in which issues relating to retirement and an ageing workforceare at the intersection of key social changes over the past decades.The authors review the various strands in current research literatureand present empirical findings which might serve as a guide todebates on the individual and societal position of older workers.

Sucrose Transporters (SUTs, also called Sucrose Carriers-SUCs) are membrane proteins, located in the plasma membrane that function in loading sucrose into phloem (specialized vascular tissue) and in sucrose uptake into sink cells. This study aims to investigate more aspects of physiological functions of sucrose transporters in solanaceae plants. There are three subfamilies of sucrose transporters (SUT1, SUT2 and SUT4) have been identified from Solanum tuberosum and Solanum lycopersicon. Genetic and biochemical evidences have established that SUT1-type proteins function in phloem loading, but the phloem specific role of SUT2 and SUT4 proteins still needs further elucidation.A series of detailed analyses of sucrose transporter mRNAs mobility and stability have been performed in this study. Parasitic and graft experiments show that SUT1 mRNAs including (StSUT1, NtSUT1, SlSUT1 and SoSUT1) are phloem mobile; relative analysis with the help of transcriptional and translational inhibitor show that, SUT1 mRNA stability is mainly regulated at the transcriptional level, whereas SUT2 and SUT4 mRNA stability is mainly regulated at the post-transcriptional level.The differential regulations show that members of the SUT2 and SUT4 family are obviously subject of a different regulatory network as described for sucrose transporters belonging to the SUT1 subfamily. In order to clarify relative physiological functions of SUT2 and SUT4 subfamilies, StSUT2 & StSUT4-RNAi potato plants were generated in this work. In addition, SlSUT4 over-expressed tobacco plants were produced and the molecular and phenotypical characters of these transgenic plants illuminated that SUT4 might serve as an inhibitor of SUT1.

Bis(phosphinimino)methanide rare earth metal bisborohydrides, as illustrated in Scheme I, were successfully synthesized by salt metathesis reactions of [K{CH(PPh2NSiMe3)2}] with [Ln(BH4)3(THF)n] (Ln = Sc (n = 2); Ln = La, Nd, Lu (n = 3)) or in the case of yttrium by the reaction of [{(Me3SiNPPh2)2CH}YCl2]2 with NaBH4. Interestingly, the BH4- anions are?3-coordinated in the solid state structures of 3, 4, 6 and 7, while for the scandium complex 5 two different conformational polymorphs were identified, in which either both BH4- groups are ?3-coordinated or one BH4- anion shows an ?2-coordination mode. Furthermore, complexes 3, 6 and 7 showed high activities in the ring-opening polymerization (ROP) ofe-caprolactone (CL). At 0 °C, the molar mass distribution reached the narrowest values ever obtained for the ROP of CL initiated by a rare earth metal borohydride species.

This book contains a selection of reports contributed to the World Housing Encyclopedia project (http://www.world-housing.net/) by the author, one of them together with Eng. Ilie Sandu. The reports were selected to highlight the difference in the building typology in Romania and Germany in vernacular and respectively Modernist housing. While in Romania brick masonry in rectangular one storey construction and reinforced concrete multistory frame were the typical structural systems, in Germany frame structure out of timber and respectively steel in multistory construction reflected the different geography of resources. Closing a report of the German colonists on the territory of today¿s Romania from about 300 years ago in Banat and in Sathmar county is included, in which the local vernacular typology of rectangular one storey brick masonry housing was practiced. The collection of reports is preceded by an essay deconstructing the term of Modernity in the dialogue traditional-modern in literature and architecture. Instead of postface conclusion are drawn on the common features and especially the differences in the two countries, relating the development also to late immigrants from Germany to Romania, as architect Rudolph Fraenkel was, who built one of the few buildings with steel structure to times of Modernism.