Browsing by Subject "Ressourcen"

Now showing 1 - 4 of 4

An integrated computable general equilibrium model including multiple types and uses of water
(2015) Luckmann, Jonas Jens; Grethe, Harald
Water is a scarce resource in many regions of the world and competition for water is an increasing problem. To countervail this trend policies are needed regulating supply and demand for water. As water is used in many economic activities, water related management decisions usually have complex implications. Economic simulation models have been proven useful to ex-ante assess the consequences of policy changes. Specifically, Computable General Equilibrium (CGE) models are very suitable to analyze the consequences of water-related management decisions, as they consider the interlinkages between different sectors and economic agents within an economy. However, so far there is no CGE model which provides a holistic picture of the water sector including all aspects of provision, demand and management. Against this background, in this thesis a CGE model (STAGE_W) is developed which is especially focused on the water sector and provides a generic, integrated and flexible framework to incorporate various water sources from which several water activities produce water commodities of differing quality. These are consumed by other activities or by households. The applications presented in this thesis are to the best knowledge of the author the first CGE approaches to depict the recycling of wastewater and the provision of brackish groundwater as independent activities. Another novelty of the model is that it is capable to depict cascading water use. Furthermore, the inclusion of several water specific taxation instruments allows for a wide range of water policy simulations. To demonstrate the capabilities of the model, STAGE_W is applied to a Social Accounting Matrix for Israel. Based on this database several case studies are conducted which are presented in three scientific articles. Israel provides an ideal example as the country is strongly affected by water scarcity and is also among the world leaders regarding the development of new water sources and technologies. In the first article, a literature review on previously existing approaches of water depiction in CGE models is provided along with a detailed description of the specifics of STAGE_W. The model is applied to simulate a reduction of freshwater resources. The effects of this shock are analyzed with and without further increasing the desalination capacity. The results show that the economic effects are slightly negative under both scenarios. Counterintuitively, the provision of additional potable water through desalination does not substantively reduce the negative outcomes. This is mainly due to the high costs of desalination, which are currently subsidized in Israel. The second article simulates an abolishment of the discriminatory water pricing system currently established in Israel. Instead, two alternative schemes are introduced: price liberalization, which unifies the prices for all potable water consumers at cost recovery rates, and marginal pricing, lifting the potable water price to the cost of desalination. It is found that both schemes yield a double dividend by simultaneously saving water and increasing economic growth. Thereby, marginal pricing allows for larger water savings while price liberalization results in higher economic growth. In the third article, the model is further refined: the quantity of sewage available for reclamation is linked to the water consumption of economic entities connected to a sewer system. This allows to depict cascading water use and to endogenously estimate the marginal value of unpurified sewage. It is shown that a consideration of this link is crucial, if a high share of potable water is reclaimed and used. In this case, reducing the potable water consumption of municipalities also negatively affects the availability of reclaimed wastewater and thereby reduces its potential as a substitute for potable water. These case studies provide evidence of the validity of the model developed. The model results cannot necessarily be anticipated, as they are the outcome of complex interrelations within the model and none of the previous models has the capacity to capture all the relevant aspects of the water sector which influence these outcomes. Therefore, it is concluded that STAGE_W constitutes a helpful tool to implement a more sustainable management of water resources, allowing policy makers to ex-ante estimate the economy-wide effects of water related decisions. As the whole economy is depicted, a more holistic picture of effects resulting from changes in the water sector can be drawn in comparison to single sector models or cost-benefit analyzes.
Multiagent resource allocation in service networks
(2014) Karänke, Paul; Kirn, Stefan
The term service network (SN) denotes a network of software services in which complex software applications are provided to customers by aggregating multiple elementary services. These networks are based on the service-oriented computing (SOC) paradigm, which defines the fundamental technical concepts for software services over electronic networks, e.g., Web services and, most recently, Cloud services. For the provision of software services to customers, software service providers (SPs) have to allocate their scarce computational resources (i.e., hardware and software) of a certain quality to customer requests. The SOC paradigm facilitates interoperability over organizational boundaries by representing business relationships on the software system level. Composite software services aggregate multiple software services into software applications. This aggregation is denoted as service composition. The loose coupling of services leads to SNs as dynamic entities with changing interdependencies between services. For composite software services, these dependencies exist across SN tiers; they result from the procurement of services, which are themselves utilized to produce additional services, and constitute a major problem for resource allocation in SNs. If these dependencies are not considered, the fulfillment of agreements may become unaccomplishable (overcommitment). Hence, the consideration of service dependencies is crucial for the allocation of service providers resources to fulfill customer requests in SNs. However, existing resource allocation methods, which could consider these dependencies -- such as combinatorial auctions with a central auctioneer for the whole SN -- are not applicable, since there are no central coordinating entities in SNs. The application of an allocation mechanism that does not consider these dependencies might negatively affect the actual service delivery; results are penalty payments as well as a damage to the reputation of the providers. This research is conducted in accordance to the design science paradigm in information system research. It is a problem-solving paradigm, which targets the construction and evaluation of IT artifacts. The objectives of this research are to develop and evaluate an allocation protocol, which can consider multi-tier service dependencies without the existence of central coordinating entities. Therefore, an interaction protocol engineering (IPE) perspective is applied to solve the problem of multi-tier dependencies in resource allocation. This approach provides a procedure model for designing interaction protocols for multiagent systems, and is closely related to the well-established area of communication protocol engineering. Automated resource allocation in SNs is analyzed in this research by representing the actors as autonomous software agents in the software system. The actors delegate their objectives to their software agents, which conduct the negotiations for service provision on their behalf. Thus, these agents communicate concerning the resource allocation; in this process, the sequence of communication interactions is crucial to the problem addressed. Interaction protocols define a structured exchange of defined messages between agents; they facilitate agent conversations. When multiple agents have to reach agreements by negotiation and bargaining, such as in case with allocating scarce resources, game theory provides means to formalize and analyze the most rational choice of actions for the interacting agents. Based on a formal framework for resource allocation in SNs, this research first performs a game-theoretic problem analysis; it is concerned with the existence, as well as the complexity of computing optimal allocations. In addition, Nash equilibria are analyzed for optimal allocations. Second, a distributed, auction-based allocation protocol, which prevents overcommitments and guarantees socially optimal allocations for single customer requests under certain assumptions, is proposed. Therefore, a game-theoretic model and an operationizable specification of the protocol are presented. Third, it is formally verified that the protocol enables multi-tier resource allocation and avoids overcommitments by proofs for the game-theoretic model and by model checking for the interaction protocol specification; using the model checker Spin, safety properties like the absence of deadlock are as well formally verified as the protocol enabling multi-tier resource allocation. Fourth, the efficacy and the benefits of the proposed protocol are demonstrated by multiagent simulation for concurrent customers. The experimental evaluation provides evidence of the protocols efficiency compared to the socially optimal allocation as a centralized benchmark in different settings, e.g., network topologies and different bidding policies.
Simultaneous lotsizing and scheduling - extensions and solution approaches
(2018) Wörbelauer, Martin; Meyr, Herbert
The present thesis focuses on simultaneous lotsizing and scheduling. A comprehensive review of the literature is presented in which the historical development of the subject and the current research gaps are, based on a classification scheme, described. Additionally, a review focusing on so-called „secondary resources“ (e.g., setup operators or raw materials), which are considered alongside the primary production resource, is provided. The insights on different types of secondary resources help to develop a new model formulation generalizing and extending the currently used approaches, which are specific to certain settings. Some illustrative examples demonstrate the functional principle and flexibility of this new formulation which can thus be used in a wide range of applications. Finally, a new heuristic to solve large-scaled simultaneous lotsizing and scheduling problems is presented. The heuristic creates a modified multi-line master problem by aggregating products into groups. The resulting problem is less complex and its solution can be used to define single-line sub problems. These sub problems are solved by heuristics present in the literature and the results are then combined to form a solution to the original problem. Numerical tests show the applicability of the aforementioned approach to solve problems of practical relevance.
With all my senses : restorative environments through holistic sensory impressions
(2017) Sona, Brid; Steidle, Anna
Growing awareness of psychological health problems is resulting in various research areas exploring new approaches to fostering personal resources. Restorative Environments Theory (RET) has shown that mundane natural environments support personal resources. Although other restorative environments may exist besides mundane natural environments, their systematic examination is still lacking. In the real world, users experience environments through all their senses. However, most of the recovery research focuses on investigation of single sensory impressions. Thus, concrete insights into how various ambient qualities of an environment may affect users’ perception are still needed. The main aim of this doctoral thesis is to enhance the existing theoretical framework of restorative environments and to give an overview of research while pointing out where more research is needed. Further, the thesis includes identification of restorative environments and their specific ambient qualities. Based on the explored environments, the present research will point out psychological pathways to obtain recommendations for the design of restorative environments. The first research project was an explorative study to identify restorative places and their ambient qualities. In accordance with restoration research, participants described natural outdoor environments which they sought for recovery. In addition, they described indoor environments. Depending on the type of depletion and the environmental setting, specific environments and ambient qualities were evaluated as more important for the restorative potential of the place than others. This explorative research supports theory building and enables creation of restorative environments through holistic sensory impressions. Finally, strengths, limitations and practical implications for designing and improving restorative environments are discussed. The second research project takes up the findings of the first project by simulating sensory-enriched break environments. Based on the impact of holistic sensory impressions, this project is one of the first to reveal the impact of the recovery process of simulated environments on personal resources through congruent sensory impressions. Analyses confirmed that sensory-enriched environments were perceived as more pleasant and more restorative than less enriched environments, which in turn facilitated the recovery of personal resources. The results point out the relevance of holistic sensory impressions to fostering recovery. Implications and limitations of sensory enrichment in break environments are discussed. To broaden generalizability, the third research project comprises three field experiments investigating recovery during break interventions which offered virtual restorative environments with differing degrees of immersion and different types of environments. Building on previous research (Grimshaw, 2014), the third project posited that a higher degree of immersion in the simulated environment increases perceived realism, which becomes apparent in higher positive perceptions and recovery outcomes. Moreover, environments with different degrees of stimulation were anticipated to evoke distinct successful recovery. Previous research had mainly focused on calming environments for recovery. Additionally, this project also tested whether stimulating environments promote recovery outcomes. Results mainly confirmed the proposed hypotheses. The relevance of immersion and the impact of different types of natural environments on recovery are discussed. Overall, the current research emphasizes the impact of holistic sensory impressions in enhancing positive perceptions of the environment and, consequently, various recovery outcomes. The conducted studies uncover the psychological pathway from the processes of sensory perception to environmental recovery perception, followed by recovery outcomes. Beside these theoretical insights, the current research delivers concrete recommendations for designing restorative (virtual) environments in the workplace.