A class of robust numerical methods for solving dynamical systems with multiple time scales

In this paper, we develop a class of robust numerical methods for solving dynamical systems with multiple time scales. We first represent the solution of a multiscale dynamical system as a transformation of a slowly varying solution. Then, under the scale separation assumption, we provide a systematic way to construct the transformation map and derive the dynamic equation for the slowly varying solution. We also provide the convergence analysis of the proposed method. Finally, we present several numerical examples, including ODE system with three and four separated time scales to demonstrate the accuracy and efficiency of the proposed method. Numerical results verify that our method is robust in solving ODE systems with multiple time scale, where the time step does not depend on the multiscale parameters

Native-like lignin for the development of lignin-focused biorefineries

Lignin, an abundant aromatic component of lignocellulosic biomass, is currently underutilized as it is often burned as an undesired side stream in the production of paper and bioethanol. This while lignin harbors great potential as source of high value aromatic chemicals and materials. Biorefineries focused on lignin are currently under development with aim of acquiring added value from lignin. However, these biorefineries are closely linked with the quality of extracted lignin. Thus, the degradation pathways of the native lignin contained in the plant material needs to be understood in detail in order to achieve higher value from lignin. Undegraded native-like lignin can provide detailed studies on the structure and reactivity of native lignin for the development of lignin-focused biorefineries. This thesis firstly gives a general introduction on the isolation of native-like lignin and its application. Then there are four experimental chapters. The first, describes the development of a reliable method for the isolation of native-like lignin. Then the isolated native-like lignin was used to study the influence of minor units and saccharides of lignin catalytic hydrogenolysis. The third, includes a detailed study on the effect of acidic deep eutectic solvents treatment on this native-like lignin. The fourth part showed development of novel ionic liquids that can mediated selective alcohol incorporation in lignin. Finally, perspectives on the use of native-like lignin on lignin-focused biorefineries are discussed. This thesis demonstrates the great potential that this type of lignin brings for understanding the effect of different biomass treatments on the native lignin structure

Refitting industrial Cerdà: reorganising Cerdà blocks with Can Ricart precinct

The layout of Poblenou is complicated, combined with many layers, including the Cerdà Grid and practices following it, different kinds of industrial heritage and its layout, etc. They are different and contradictory, for carried out in different historical periods and from architectural thoughts. As Cerdà grid gradually approaching, many of industrial heritage sunk and scattered into the orthogonal grid. The old layout has been dissolved into new context. However, they brought ´diversity´ to Cerdà grid, which is the crucial value in the evolution of Cerdà in Poblenou. It naturally generates chances for evolution of new Cerdà to accommodate and integrate various and contradictory elements here, and can be identified as ´Industrial Cerdà´. Thus, ´Industrial Cerdà´ in Poblenou should not be simply described as ´orthogonal grid´, but the carrier of diversity and ´non-Cerdà´ layers in Poblenou as well. Thus, thesis mainly focuses on three basic question: How to insert industrial heritage into Cerdà block? How can industrial heritage refit the form of Cerdà? And how to integrate them together? The thesis will be divided into 3 aspects. Firstly, standard Cerdà, as well as many orthogonal planning in history, emphasizes the concept of ´unit´ and their solutions of generating public spaces. It shows a critical idea of individual but common cluster for safety and sense of belonging, while assembled for urban spaces. Thus, they are not enclosed, with some connections to context. Among some new Cerdà blocks in Poblenou, courtyards are reorganised as urban space in larger scale. Secondly, Cerdà plan can never be perfect standard model. Exceptional plots of it create horizontal diversity to various circumstances for Cerdà practices. It emerged from compromises when facing with reality, including function, entrance, landmark, etc. In order to establish positive interactions between courtyard and context with visual, functional and mobility connections in different types in different parts of a standard model. Thirdly, industrial heritages and its layout are supposed to contribute to reform of Cerdà blocks to improve the quality of pedestrian level spaces of Poblenou, which can be achieved by overlapping. Many architects expressed their ideas of integration different layers of activities and context, which could help to create vertical diversity for Cerdà forms. Meanwhile, heritages can also be well absorbed in pedestrian spaces for city life. To take Can Ricart as example, this thesis aims to practise formal strategies for industrial heritage to refit in Cerdà block in Poblenou, and also help them to assimilate into new communities there