Environmental Policy and Optimal Taxation in a Decentralized Economic Federation

This paper deals with environmental policy in an economic federation, where each national government faces a mixed tax problem. We assume that the federal government sets emission targets, which are implemented at the national level. We also assume that the economic federation is decentralized, meaning that the national governments are first movers vis-a-vis the federal government. Our results show that each country uses it policy instruments, at least in part, to influence the emission target. This has several implications; first, the commodity taxes do not satisfy the so called additivity property often emphasized in earlier literature and, second, it provides an argument for using distortionary labor income taxation.Income and commodity taxation; economic federation; environmental policy

Food webs coupled in space: Consumer foraging movement affects both stocks and fluxes

The exchange of material and individuals between neighboring food webs is ubiquitous and affects ecosystem functioning. Here, we explore animal foraging movement between adjacent, heterogeneous habitats and its effect on a suite of interconnected ecosystem functions. Combining dynamic food web models with nutrient-recycling models, we study foraging across habitats that differ in fertility and plant diversity. We found that net foraging movement flowed from high to low fertility or high to low diversity and boosted stocks and flows across the whole loop of ecosystem functions, including biomass, detritus, and nutrients, in the recipient habitat. Contrary to common assumptions, however, the largest flows were often between the highest and intermediate fertility habitats rather than highest and lowest. The effect of consumer influx on ecosystem functions was similar to the effect of increasing fertility. Unlike fertility, however, consumer influx caused a shift toward highly predator-dominated biomass distributions, especially in habitats that were unable to support predators in the absence of consumer foraging. This shift resulted from both direct and indirect effects propagated through the interconnected ecosystem functions. Only by considering both stocks and fluxes across the whole loop of ecosystem functions do we uncover the mechanisms driving our results. In conclusion, the outcome of animal foraging movements will differ from that of dispersal and diffusion. Together we show how considering active types of animal movement and the interconnectedness of ecosystem functions can aid our understanding of the patchy landscapes of the Anthropocene

Conceptual data systems architecture principles for information systems

Information systems alignment with enterprise evolution affects the performance of enterprises. The systems conceptual and data quality, development time and sustainable life cycle management, are issues for enterprise competitiveness. The ability to directly generate enterprise information systems from models has been thought of as a solution to improve on these issues. Model-driven systems have been a research topic for decades. Fundamental principles for a proven model-driven information systems architecture are outlined in this article. Architectural foundation is a separation of user communities conceptual domain from the information technical domain. The users domain is modeled as an information system model in three layers, conceptual data logic model, interface model and user community model. The technical domain is a platform, allowing the modeling and execution of such a model. These principles have been applied in practice and proven viable. Two platforms and applications, which adhere to these principles, are briefly described

Characterization of the BOLD signal in functional MRI

In the last two decades, functional magnetic resonance imaging (fMRI) has become an important and widely used imaging technique for functional brain mapping. However, blood oxygen level dependent (BOLD) technique is quite insensitive and task invoked BOLD signal change at 3T is typically in the order of a few percent. Furthermore, the coupling between BOLD signal changes and neuronal activities is quite complicated, involving a cascade of events remaining poorly understood even today. In this thesis, some of the basic characteristics of the BOLD signal are investigated. Better understanding of the BOLD signal characteristics can be beneficial for the design of BOLD fMRI experiment aimed to improve the time efficiency. It can also provide guidelines for developing fMRI data processing strategies. In study I and II, a single-shot dual-echo spiral acquisition technique was used for characterizing the T2* changes associated with motor activation task. In study I, the optimal strategy for head motion correction was investigated. Based on the improvement in the detection of brain activation, the best strategy is to perform the head motion correction using the imaging data from the second echo and then apply the derived motion correction parameters to the first echo, instead of conducting motion correction of the individual echoes independently. In study II, several aspects of brain mapping methods based on T2*-weighted imaging and T2* (R2*=1/T2*) mapping were quantitatively compared, including the detected activation volume, functional contrast, signal-to-noise ratio, and contrast-to-noise ratio. fMRI studies based T2* mapping have the following potential advantages: maximum functional contrast, independence of echo time; and reduced inflow effects. The sensitivity for brain activation detection is significantly correlated with the contrast-to-noise ratio, which is determined by both the signal-to-noise ratio and functional contrast. In study III, the hemodynamic responses to functional activation were characterized using T2*-weighted BOLD imaging, arterial spin labeling, and bolus tracking of MRI contrast agent. In addition to the BOLD signal change, the relative cerebral blood flow and cerebral blood volume associated with brain activation were independently determined. In study IV, the characteristics of the global signal in resting-state fMRI were investigated. It was found that the global signal time courses and regional contributions differ individually. However, after removing the contribution from the cerebral spinal fluid, a consistent brain network responsible for the remaining global signal changes was identified. The involved brain regions include: posterior cingulate cortex, precuneus, superior temporal gyrus, medial frontal gyrus and the cerebellar vermis, which is likely to be related to the perception and cognitive processes of the brain occurred in the specific environments during resting-state fMRI

Effects of Core-valence and Core-core Correlation On the Line-strength of the Resonance Lines In Li-i and Na-i

The resonance lines in Li I and Na I both exhibit a puzzling discrepancy between experiment and accurate ab initio calculations. Only results from a semiempirical method, that in principal neglects core-core correlation, agree with the experiments. The agreement with a multiconfiguration Hartree-Fock calculation, including only core-valence correlation, shows that this might be fortuitous. A method for including some core-core correlation is designed and gives results in excellent agreement with other accurate ab initio methods

Conceptual Design of a Compressor Vane- HEX for LH2 Aircraft Engine Applications

In order to meet the ambitious environmental targets set by the Paris Agreement, new sustainable carbon neutral aviation fuels need to be introduced. The high gravimetry energy density of hydrogen, makes it a prime candidate for a future aviation fuel. However, the associated poor volumetric energy density, requires an increased aircraft volume and associated penalty in aerodynamic performance. The required volume occupied by the hydrogen fuel can be decreased in half, if stored in its liquid form. This however requires that the liquid hydrogen (LH2) is kept at cryogenic temperatures, requiring adequate tank insulation. Moreover, to increase the effective heating value of hydrogen, the fuel distribution system will include heat exchanger technology to increase the fuel temperature before injection in the combustion chamber. The present work provides an outlook of different heat exchanger technology for application in hydrogen fueled gas turbine aero engines. The heat exchangers can be placed in the vicinity of the engine to reject the heat generated by the gas core to the hydrogen fuel. Ideally, they are strategically located to use heat management to maximize the engine efficiency and ensuring sufficient component durability. Moreover, the combination of liquid hydrogen’s high specific heat with cryogenic storage temperatures results in a formidable cooling capacity that can be explored by more compact heat exchanger solutions

Design of Chalmers new low-pressure compressor test facility for low-speed testing of cryo-engine applications

As a part of the ongoing Horizon 2020 ENABLEH2 project, a new low-speed compressor test facility is being constructed at the Chalmers University Laboratory of Fluids and Thermal Sciences. The ENABLEH2 project investigates critical technologies for cryogenic H2 applications in commercial aviation, including new combustion and heat management systems. This paper revolves around the design and construction of a core cooling flow facility which was commissioned to study and verify the potential benefits of incorporating a heat management system into the intermediate compressor duct (ICD).The test facility is designed to operate continuously at rotor midspan chord Reynolds number up to 600,000 to allow for detailed aerothermal studies at a technical readiness level four. The two-stage axial compressor is representative of the low-pressure compressor and ICD of a mid-size commercial jet engine. The compressor is powered by a 147kW electric motor at 1920 RPM. The mass-flow and pressure ratio are controlled by restricting valves located at the inlet of the facility. A compact volute settling chamber, with an integrated thermal control system is used to control the inlet temperature and remove flow non-uniformities downstream the restrictor valves before entering the compressor. At the compressor inlet, a turbulence mesh is mounted to increase the turbulence intensity levels to 3-4% at the leading edge of the variable inlet guide vanes. The compressor is mounted vertically to allow for easy access to the downstream ICD and mitigate non-axisymmetric mechanical loads. The compressor unit allows for optical and traverse access at two +- 9-degree sectors for all the rotor-stator interfaces. Upstream the OGV, there are four independent $\pm$ 180-degree access traverse systems. In the ICD, measurements are carried out by a single ABB robot with a U-shaped probe mount, providing full volume probing access of the ICD. At the first design iteration the ICD is designed to be instrumented with multi-hole probes, hot-wire anemometry and heat transfer measurement using IR-thermography.The paper describes the facility and the process of achieving a high case similarity (engine representative) while maximising the quality of the experimental data over a large test domain, targets that often produce conflicting design demands

Development of fuel and heat management systems for liquid hydrogen powered aircraft

The presentation describes the recent developments in the design of the fuel and heat management systems for liquid hydrogen powered aircraft within the H2020 project ENABLEH2. The fuel distribution system main task is to deliver the right amount of hydrogen to the combustion chamber at an adequate pressure. This requires the usage of fuel pumps, valves, insulated piping, and a fuel control system to adjust the fuel flow for a given engine rating. Moreover, since liquid hydrogen is stored at cryogenic temperatures (-253C), it also requires the integration of heat exchanger technology to increase the fuel temperature up to a state where it can be efficiently mixed with air and combusted. The combination of hydrogen high specific heat with cryogenic temperatures results in formidable cooling capacity that can be explored by compact heat-exchanger solutions. Concepts that use existing engine aero-surfaces located after rotating turbomachinery are currently being investigated a Chalmers University of Technology.\ua0 A recently commissioned facility to investigate the potential benefits of a compressor flow cooling heat rejection system will also be discussed.\ua0 The test facility comprises a vertically mounted low-speed 2.5 stage compressor designed to operate continuously at rotor mid-span chord Reynold number up to 600,000, which is representative of a large-size future geared turbofan engine. Detailed aerothermal studies at TRL4 will be conducted to calibrate in-house design methods for radical core integrated heat exchangers. The facility is driven by a 147kW electric drive at a nominal speed of 1920 RPM. Traverse access is included in two 18-degree sectors for all the rotor-stator interfaces. At the upstream plane of the compressor outlet-guide-vane, four independent access traverse systems are included for a 360-degree access. Downstream, an ABB robot arm with a U-shaped probe mount provides full volume probing access in the exit compressor duct