THE CALCIUM LOOPING CYCLE STUDY FOR CAPTURING CARBON DIOXIDE APPLIED TO THE ENERGY GENERATION

The calcium looping process (Ca-L) is a promising technology to reduce of the carbon dioxide (CO2) emissions when applied in energy generation systems. Ca-based materials (usually limestone) are used in this process as CO2 sorbents. Thus, the CO2 capture occurs by the reversible reaction between calcium oxide (CaO) and CO2, resulting in the calcium carbonate form (CaCO3). Compared to other technologies applied to carbon sequestration process, the Ca-L offers additional advantages such: the use of fluidized bed technology that is already well established; this process occurs at high temperature, and the excess of heat generated can be recovered; the cost of limestone sorbents is low because of its wide availability. However, in the applying the Ca-L process is essential to understand the mechanism and the effect of partial pressure of CO2 in both, calcination and carbonation processes; to investigate the effect of sintering and to evaluate the sorbent activity decay. In this paper, empirical technique such as thermogravimetry is applied to investigate the reactivity of dolomite as CO2 sorbent. The effect of CO2 high concentrations in both calcination/carbonation processes is also investigated

Towards a European master programme on global software engineering

This paper presents a European Master programme on global software engineering (SE), being put forward by four leading institutions from Sweden, UK, Netherlands and Italy. The Global SE European Master (GSEEM) programme aims to provide students with an excellence in SE based on sound theoretical foundations and practical experience, as well as prepare them to participate in global development of complex and large software systems. GSEEM has been designed with three noteworthy aspects: 1) Three specialization profiles in which the consortium excels: Software Architecting, Real-time Embedded Systems Engineering, and Web Systems and Services Engineering. 2) Two market-driven routes: "professional" to work as professionals, and "scientific" to continue the education towards research degrees. 3) An innovative concept of "shared modules", delivered together by multiple institutions. Four types of shared modules are foreseen: "parallel" twin modules which run remotely between universities, "shifted" modules which teach SE concepts incrementally with shifts in study locations and timeline ,"complementary" modules in which complementary SE concepts are taught in parallel through shared projects, and "common" modules which share the presentations and the project. The profiles realize "integrated knowledge" by complementing partial knowledge available at partner institutions. The paper explains how GSEEM achieves the objectives of educating global software engineers

STUDY OF THERMAL DECOMPOSITION AND IGNITION TEMPERATURE OF BAGASSE, COAL AND THEIR BLENDS

In Brazil, due to its availability, sugar cane bagasse has a high potential for power generation. The knowledge of ignition behavior, as well as the knowledge of the chemical kinetics, in of fuels combustion process is important features in boilers projects and in the stability of the combustion process control. The aim of this study is to investigate the thermal behavior of sugar cane bagasse, coal and their blends. The methodology proposed by Tognotti et al. (1985) was applied to determine the ignition temperature for all samples. Ignition temperatures were 256oC for neat bagasse and 427oC for neat coal, and 275oC for both blends (50-50% and 25-75%). The Model-Free Kinetics was applied to determine the apparent activation energy (Eα) of the thermal decomposition of sugar cane bagasse. For the two major events of mass loss of bagasse which correspond to the thermal decomposition of organic matter (mainly hemicellulose, cellulose and lignin), average values of Eα were obtained for both combustion and pyrolysis processes. In synthetic air atmosphere, the Eα were 170.8±26.3 kJ⋅mol-1 and 277.8±58.6 kJ⋅mol-1, while in nitrogen atmosphere, the Eα were 185.0 ± 11.4 kJ⋅mol-1 and 82.1±44.4 kJ⋅mol-1. The results obtained can be explained by synergistic effects when both bagasse and coal were blended, changing the fuel reactivity

Accelerated test execution using GPUs

As product life-cycles become shorter and the scale and complexity of systems increase, accelerating the execution of large test suites gains importance. Existing research has primarily focussed on techniques that reduce the size of the test suite. By contrast, we propose a technique that accelerates test execution, allowing test suites to run in a fraction of the original time, by parallel execution with a Graphics Processing Unit (GPU). Program testing, which is in essence execution of the same program with multiple sets of test data, naturally exhibits the kind of data parallelism that can be exploited with GPUs. Our approach simultaneously executes the program with one test case per GPU thread. GPUs have severe limitations, and we discuss these in the context of our approach and define the scope of our applications. We observe speed-ups up to a factor of 27 compared to single-core execution on conventional CPUs with embedded systems benchmark programs

Alpha decay and proton-neutron correlations

We study the influence of proton-neutron (p-n) correlations on alpha-decay width. It is shown from the analysis of alpha Q values that the p-n correlations increase the penetration of the alpha particle through the Coulomb barrier in the treatment following Gamow's formalism, and enlarges the total alpha-decay width significantly. In particular, the isoscalar p-n interactions play an essential role in enlarging the alpha-decay width. The so-called "alpha-condensate" in Z > 84 isotopes are related to the strong p-n correlations.Comment: 5 pages, 6 figures, accepted for publication in Phys. Rev. C (R.C.

Symmetry Breaking in the Double-Well Hermitian Matrix Models

We study symmetry breaking in $Z_2$ symmetric large $N$ matrix models. In the planar approximation for both the symmetric double-well $\phi^4$ model and the symmetric Penner model, we find there is an infinite family of broken symmetry solutions characterized by different sets of recursion coefficients $R_n$ and $S_n$ that all lead to identical free energies and eigenvalue densities. These solutions can be parameterized by an arbitrary angle $\theta(x)$, for each value of $x = n/N < 1$. In the double scaling limit, this class reduces to a smaller family of solutions with distinct free energies already at the torus level. For the double-well $\phi^4$ theory the double scaling string equations are parameterized by a conserved angular momentum parameter in the range $0 \le l < \infty$ and a single arbitrary $U(1)$ phase angle.Comment: 23 pages and 4 figures, Preprint No. CERN-TH.6611/92, Brown HET-863, HUTP -- 92/A035, LPTHE-Orsay: 92/2

Applications of Temperley-Lieb algebras to Lorentz lattice gases

Motived by the study of motion in a random environment we introduce and investigate a variant of the Temperley-Lieb algebra. This algebra is very rich, providing us three classes of solutions of the Yang-Baxter equation. This allows us to establish a theoretical framework to study the diffusive behaviour of a Lorentz Lattice gas. Exact results for the geometrical scaling behaviour of closed paths are also presented.Comment: 10 pages, latex file, one figure(by request

Deformation Quantization of Bosonic Strings

Deformation quantization of bosonic strings is considered. We show that the light-cone gauge is the most convenient classical description to perform the quantization of bosonic strings in the deformation quantization formalism. Similar to the field theory case, the oscillator variables greatly facilitates the analysis. The mass spectrum, propagators and the Virasoro algebra are finally described within this deformation quantization scheme.Comment: 33+1 pages, harvmac file, no figure

Currents and Superpotentials in classical gauge theories: II. Global aspects and the example of Affine gravity

The conserved charges associated to gauge symmetries are defined at a boundary component of space-time because the corresponding Noether current can be rewritten on-shell as the divergence of a superpotential. However, the latter is afflicted by ambiguities. Regge and Teitelboim found a procedure to lift the arbitrariness in the Hamiltonian framework. An alternative covariant formula was proposed by one of us for an arbitrary variation of the superpotential, it depends only on the equations of motion and on the gauge symmetry under consideration. Here we emphasize that in order to compute the charges, it is enough to stay at a boundary of spacetime, without requiring any hypothesis about the bulk or about other boundary components, so one may speak of holographic charges. It is well known that the asymptotic symmetries that lead to conserved charges are really defined at infinity, but the choice of boundary conditions and surface terms in the action and in the charges is usually determined through integration by parts whereas each component of the boundary should be considered separately. We treat the example of gravity (for any space-time dimension, with or without cosmological constant), formulated as an Affine theory which is a natural generalization of the Palatini and Cartan-Weyl (vielbein) first order formulations. We then show that the superpotential associated to a Dirichlet boundary condition on the metric (the one needed to treat asymptotically flat or AdS spacetimes) is the one proposed by Katz, Bi\u{c}{\'a}k and Lynden-Bell and not that of Komar. We finally discuss the KBL superpotential at null infinity.Comment: 16 pages, minor corrections and references added. Final version to appear in CQ

Understanding and Supporting Software Architectural Decisions

Samenvatting De architectuur van software systemen wordt bepaald door de architectuur beslissingen. Hierin worden onderwerpen als frameworks, patterns, programmeer talen behandeld, of manieren om het systeem op te delen. Deze beslissingen en hun rationale zijn een belangrijk onderdeel van de architectuur kennis van een software systeem. Architectuur kennis van software systemen kan verloren gaan. Een architect kan de redenen van een beslissing vergeten, een andere baan krijgen, of de documentatie van beslissingen uitstellen. Het verdwijnen van architectuur kennis heeft enorme consequenties. Het kan zijn dat de initieel beoogde architectuur ideeën niet meer kunnen worden nageleefd waardoor uitbreidingen duur worden en het moeilijk is om de consistentie tussen beslissingen te bewaren. Het hoofddoel van dit onderzoek is het verminderen van het verlies van deze architectuur kennis. Dit word gedaan door deze beslissingen en hun rationale beter te documenteren. De bijdrage van dit onderzoek bestaat uit drie fasen: het begrijpen van het huidige onderzoek en de praktijk, exploreren van nieuwe ideeën en het aandragen van een concrete aanpak om het verlies van achitectuurkennis tegen te gaan. Abstract The architecture of a software system is the result of architectural decisions on various topics, such as frameworks, patterns, programming languages, or ways to decompose the software system. Such decisions and their rationales are a significant part of the architectural knowledge about a software system. Architectural knowledge about a software system tends to vaporize. For example, architects might forget the rationales of decisions, change jobs, or postpone indefinitely documenting decisions to avoid disrupting their design flow. Architectural knowledge vaporization has major practical consequences, such as drifting away from the initially intended architecture, and expensive evolution, due to the substantial needed effort to understand previous decisions and to avoid conflicts with them. The overall research problem addressed in this thesis is how to reduce architectural knowledge vaporization. The overall solution is to reduce architectural knowledge vaporization by documenting architectural decisions and their rationales. The contributions of this thesis at solving this problem can be grouped in three phases: understanding the state of practice and research, exploring new ideas, and proposing concrete approaches to reduce architectural knowledge vaporization. In the first phase (understanding), we investigated the state of practice in which architectural knowledge vaporization occurs, and the state of research that can help reduce architectural knowledge vaporization. To understand the state of practice, we conducted two surveys with practitioners. The first survey helps researchers understand the challenges for managing architectural knowledge in practice, and potential solutions to these challenges. The results of the first survey indicate that architectural knowledge vaporization is a major challenge in the industry, and that tool support is a potential solution. The second survey describes real-world architectural decisions, such as their characteristics, difficulties, and differences between good and bad architectural decisions. For example, we found out that most architectural decisions are group decisions. To understand the state of research, we conducted a systematic mapping study on the last decade of research on architectural decisions. This study helped us understand existing work on reducing architectural knowledge vaporization and future promising research directions. For example, we identified a lack of research on group architectural decisions, despite the fact that most architectural decisions are group decisions. Furthermore, we identified very few open-source tools for architectural decisions. In the second phase (exploring), we investigated using established approaches from the knowledge engineering field for reducing architectural knowledge vaporization. In particular, we conducted two surveys with students on using the Repertory Grid technique for documenting architectural decisions, to identify advantages and disadvantages of the technique. We found out that the main advantages are reducing architectural knowledge vaporization and reasoning support. The main disadvantages are the needed effort and lack of user-friendly tool support. In the third phase (proposing), we made three contributions. First, we contributed an approach based on the Repertory Grid technique for making and documenting individual architectural decisions. We did a survey with practitioners to identify advantages, disadvantages, and improvement opportunities of the approach. Advantages include reduction of architectural knowledge vaporization, and decision making support. Disadvantages include effort and insufficient tool support. Improvement opportunities include support for prioritizing concerns and for group decision making. To improve the approach, we did a controlled experiment with students to compare two concerns prioritization methods, and then we added the most suitable method to the approach. Second, we contributed an extension of the approach for making and documenting group architectural decisions. We did a case study to identify benefits and potential improvements of the approach. Benefits include reduction of architectural knowledge vaporization, and increased consensus of the group. Furthermore, we did a controlled experiment with students to compare the approach against ad-hoc group decision making. Experiment results indicate that the proposed approach reduces architectural knowledge vaporization and increases consensus. vii Third, we contributed with user friendly, open-source tool support for the two approaches for making and documenting individual and group architectural decisions. Overall, the contributions of this thesis help practitioners reduce architectural knowledge vaporization. Furthermore, the contributions of this thesis help researchers understand various aspects of architectural decisions and architectural knowledge, so that researchers can propose approaches that satisfy the needs of practitioners. i