Compostabilidad de envases de bolsas de PBAT+PLA y envases r��gidos de PLA mediante tecnolog��as de pila y t��nel

Los pol��meros compostables suponen en torno al 30% de los biopl��sticos destinados a envasado, siendo a su vez esta aplicaci��n el principal destino de la producci��n de este tipo de materiales que, en el a��o 2013, super�� 1,6 millones de toneladas. La presente tesis aborda la biodegradaci��n de los residuos de envases dom��sticos compostables en medio aerobio para dos tipos de formato y materiales, envase r��gido de PLA (Clase I) y dos tipos de bolsas de PBAT+PLA (Clases II y III). Sobre esta materia se han realizado diversos estudios en escala de laboratorio pero para otro tipo de envases y biopol��meros y bajo condiciones controladas del compost con alguna proyecci��n particularizada en plantas. La presente tesis da un paso m��s e investiga el comportamiento real de los envases pl��sticos compostables en la pr��ctica del compostaje en tecnolog��as de pila y t��nel, tanto a escala piloto como industrial, dentro del procedimiento y con las condiciones ambientales de instalaciones concretas. Para ello, con el m��todo seguido, se han analizado los requisitos b��sicos que debe cumplir un envase compostable, seg��n la norma UNE ��� EN 13432, evaluando el porcentaje de biodegradaci��n de los envases objeto de estudio, en funci��n de la p��rdida de peso seco tras el proceso de compostaje, y la calidad del compost obtenido, mediante an��lisis f��sico-qu��mico y de fitotoxicidad para comprobar que los materiales de estudio no aportan toxicidad. En cuanto a los niveles de biodegrabilidad, los resultados permiten concluir que los envases de Clase I se compostan adecuadamente en ambas tecnolog��as y que no requieren de unas condiciones de proceso muy exigentes para alcanzar niveles de biodegradaci��n del 100%. En relaci��n a los envases de Clase II, se puede asumir que se trata de un material que se composta adecuadamente en pila y t��nel industrial pero que requiere de condiciones exigentes para alcanzar niveles de biodegradaci��n del 100% al afectarle de forma clara la ubicaci��n de las muestras en la masa a compostar, especialmente en el caso de la tecnolog��a de t��nel. Mientras el 90% de las muestras alcanza el 100% de biodegradaci��n en pila industrial, tan s��lo el 50% lo consigue en la tecnolog��a de t��nel a la misma escala. En cuanto a los envases de Clase III, se puede afirmar que es un material que se composta adecuadamente en t��nel industrial pero que requiere de condiciones de cierta exigencia para alcanzar niveles de biodegradaci��n del 100% al poderle afectar la ubicaci��n de las muestras en la masa a compostar. El 75% de las muestras ensayadas en t��nel a escala industrial alcanzan el 100% de biodegradaci��n y, aunque no se ha ensayado este tipo de envase en la tecnolog��a de pila al no disponer de muestras, cabe pensar que los resultados de biodegrabilidad que hubiera podido alcanzar habr��an sido, como m��nimo, los obtenidos para los envases de Clase II, al tratarse de materiales muy similares en composici��n. Por ��ltimo, se concluye que la tecnolog��a de pila es m��s adecuada para conseguir niveles de biodegradaci��n superiores en los envases tipo bolsa de PBAT+PLA. Los resultados obtenidos permiten tambi��n sacar en conclusi��n que, en el dise��o de instalaciones de compostaje para el tratamiento de la fracci��n org��nica recogida selectivamente, ser��a conveniente realizar una recirculaci��n del rechazo del afino del material compostado para aumentar la probabilidad de someter este tipo de materiales a las condiciones ambientales adecuadas. Si adem��s se realiza un triturado del residuo a la entrada del proceso, tambi��n se aumentar��a la superficie espec��fica a entrar en contacto con la masa de materia org��nica y por tanto se favorecer��an las condiciones de biodegradaci��n. En cuanto a la calidad del compost obtenido en los ensayos, los resultados de los an��lisis f��sico ��� qu��micos y de fitotoxicidad revelan que los niveles de concentraci��n de microorganismo pat��genos y de metales pesados superan, en la pr��ctica totalidad de las muestras, los niveles m��ximos permitidos en la legislaci��n vigente aplicable a productos fertilizantes elaborados con residuos. Mediante el an��lisis de la composici��n de los envases ensayados se constata que la causa de esta contaminaci��n reside en la materia org��nica utilizada para compostar en los ensayos, procedente del residuo de origen dom��stico de la denominada ���fracci��n resto���. Esta conclusi��n confirma la necesidad de realizar una recogida selectiva de la fracci��n org��nica en origen, existiendo estudios que evidencian la mejora de la calidad del residuo recogido en la denominada ���fracci��n org��nica recogida selectivamente��� (FORM). Compostable polymers are approximately 30% of bioplastics used for packaging, being this application, at same time, the main destination for the production of such materials exceeded 1.6 million tonnes in 2013. This thesis deals with the biodegradation of household packaging waste compostable in aerobic medium for two format types and materials, rigid container made of PLA (Class I) and two types of bags made of PBAT + PLA (Classes II and III). There are several studies developed about this issue at laboratory scale but for other kinds of packaging and biopolymers and under composting controlled conditions with some specifically plants projection. This thesis goes one step further and researches the real behaviour of compostable plastic packaging in the composting practice in pile and tunnel technologies, both at pilot and industrial scale, within the procedure and environmental conditions of concrete devices. Therefore, with a followed method, basic requirements fulfilment for compostable packaging have been analysed according to UNE-EN 13432 standard. It has been assessed the biodegradability percentage of the packaging studied, based on loss dry weight after the composting process, and the quality of the compost obtained, based on physical-chemical analysis to check no toxicity provided by the studied materials. Regarding biodegradability levels, results allow to conclude that Class I packaging are composted properly in both technologies and do not require high exigent process conditions for achieving 100% biodegradability levels. Related to Class II packaging, it can be assumed that it is a material that composts properly in pile and tunnel at industrial scale but requires exigent conditions for achieving 100% biodegradability levels for being clearly affected by sample location in the composting mass, especially in tunnel technology case. While 90% of the samples reach 100% of biodegradation in pile at industrial scale, only 50% achieve it in tunnel technology at the same scale. Regarding Class III packaging, it can be said that it is a material properly composted in tunnel at industrial scale but requires certain exigent conditions for reaching 100% biodegradation levels for being possibly affected by sample location in the composting mass. The 75% of the samples tested in tunnel at industrial scale reaches 100% biodegradation. Although this kind of packaging has not been tested on pile technology due to unavailability of samples, it is judged that biodegradability results that could be reached would have been, at least, the same obtained for Class II packaging, as they are very similar materials in composition. Finally, it is concluded that pile technology is more suitable for achieving highest biodegradation levels in bag packaging type of PBAT+PLA. Additionally, the obtained results conclude that, in the designing of composting devices for treatment of organic fraction selectively collected, it would be recommended a recirculation of the refining refuse of composted material in order to increase the probability of such materials to expose to proper environmental conditions. If the waste is grinded before entering the process, the specific surface in contact with organic material would also be increased and therefore biodegradation conditions would be more favourable. Regarding quality of the compost obtained in the tests, physical-chemical and phytotoxicity analysis results reveal that pathogen microorganism and heavy metals concentrations exceed, in most of the samples, the maximum allowed levels by current legislation for fertilizers obtained from wastes. Composition analysis of tested packaging verifies that the reason for this contamination is the organic material used for composting tests, comes from the household waste called ���rest fraction���. This conclusion confirms the need of a selective collection of organic fraction in the origin, as existing studies show the quality improvement of the waste collected in the so-called ���organic fraction selectively collected��� (FORM).

A technique for recursive invariance detection and selective program specialization

This paper presents a technique for achieving a class of optimizations related to the reduction of checks within cycles. The technique uses both Program Transformation and Abstract Interpretation. After a ��rst pass of an abstract interpreter which detects simple invariants, program transformation is used to build a hypothetical situation that simpli��es some predicates that should be executed within the cycle. This transformation implements the heuristic hypothesis that once conditional tests hold they may continu�� doing so recursively. Specialized versions of predicates are generated to detect and exploit those cases in which the invariance may hold. Abstract interpretation is then used again to verify the truth of such hypotheses and con��rm the proposed simpli��cation. This allows optimizations that go beyond those possible with only one pass of the abstract interpreter over the original program, as is normally the case. It also allows selective program specialization using a standard abstract interpreter not speci��cally designed for this purpose, thus simplifying the design of this already complex module of the compiler. In the paper, a class of programs amenable to such optimization is presented, along with some examples and an evaluation of the proposed techniques in some application ��reas such as floundering detection and reducing run-time tests in automatic logic program parallelization. The analysis of the examples presented has been performed automatically by an implementation of the technique using existing abstract interpretation and program transformation tools.

Heap analysis in the presence of collection libraries

Memory analysis techniques have become sophisticated enough to model, with a high degree of accuracy, the manipulation of simple memory structures (finite structures, single/double linked lists and trees). However, modern programming languages provide extensive library support including a wide range of generic collection objects that make use of complex internal data structures. While these data structures ensure that the collections are efficient, often these representations cannot be effectively modeled by existing methods (either due to excessive analysis runtime or due to the inability to represent the required information). This paper presents a method to represent collections using an abstraction of their semantics. The construction of the abstract semantics for the collection objects is done in a manner that allows individual elements in the collections to be identified. Our construction also supports iterators over the collections and is able to model the position of the iterators with respect to the elements in the collection. By ordering the contents of the collection based on the iterator position, the model can represent a notion of progress when iteratively manipulating the contents of a collection. These features allow strong updates to the individual elements in the collection as well as strong updates over the collections themselves.

Drifting plasma collection by a positive biased tether wire in LEO-like plasma conditions: current measurement and plasma diagnostic

BETs is a three-year project financed by the Space Program of the European Commission, aimed at developing an efficient deorbit system that could be carried on board any future satellite launched into Low Earth Orbit (LEO). The operational system involves a conductive tape-tether left bare to establish anodic contact with the ambient plasma as a giant Langmuir probe. As a part of this project, we are carrying out both numerical and experimental approaches to estimate the collected current by the positive part of the tether. This paper deals with experimental measurements performed in the IONospheric Atmosphere Simulator (JONAS) plasma chamber of the Onera-Space Environment Department. The JONAS facility is a 9- m3 vacuum chamber equipped with a plasma source providing drifting plasma simulating LEO conditions in terms of density and temperature. A thin metallic cylinder, simulating the tether, is set inside the chamber and polarized up to 1000 V. The Earth's magnetic field is neutralized inside the chamber. In a first time, tether collected current versus tether polarization is measured for different plasma source energies and densities. In complement, several types of Langmuir probes are used at the same location to allow the extraction of both ion densities and electron parameters by computer modeling (classical Langmuir probe characteristics are not accurate enough in the present situation). These two measurements permit estimation of the discrepancies between the theoretical collection laws, orbital motion limited law in particular, and the experimental data in LEO-like conditions without magnetic fields. In a second time, the spatial variations and the time evolutions of the plasma properties around the tether are investigated. Spherical and emissive Langmuir probes are also used for a more extensive characterization of the plasma in space and time dependent analysis. Results show the ion depletion because of the wake effect and the accumulation of- ions upstream of the tether. In some regimes (at large positive potential), oscillations are observed on the tether collected current and on Langmuir probe collected current in specific sites.