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This thesis deals with the designing of a garbage collector for the PNtalk virtual machine. It describes and rates the approaches and algorithms for an automatic memory management. Four algorithm families ale presented: mark-sweep, mark-compact, copying algorithms and reference counting. At first it describes sequential forms, that pauses running of the main program (mutator), then it describes parallel and concurent forms, that do not pauses the mutator. The thesis also presents generational model of garbage collecting. The following sections briefly introduces object orientated Petri nets. The result of this thesis is the design of the generational garbage collector for the PNtalk virtual machine.

We present a distributed garbage collection algorithm for Java distributed objects using the object model provided by the Java Support for Distributed Objects (JSDA) object model and using weak references in Java. The algorithm can also be used for any other Java based distributed object models that use the stub-skeleton paradigm. Furthermore, the solution could also be applied to any language that supports weak references as a mean of interaction with the local garbage collector. We also give a formal definition and a proof of correctness for the proposed algorithm.

The design of a waste collection system affects public health, the extent of participation in the system by residents, the recovery of resources from waste, and the cost of collection. Many developing countries use communal container collection [CCC] systems in which large containers are dispersed throughout neighbourhoods for the storage of waste until collection. These systems tend to have limited success as they often do not garner viable amounts of participation and containers are prone to being overfilled. The communal container waste collection system in the city of Aguascalientes, AGS, Mexico was assessed according to the Integrated Solid Waste Management [ISWM] principles of social acceptability, environmental effectiveness, economic affordability and effective management. Information was collected through seven interviews with waste-related managers, 282 residential questionnaires, and 12 informal collector questionnaires. The collection system garners a high participation rate (99%) attributed to: non-burdensome one-way distances from residences to containers (mean 114+/-71m); thorough, daily collection; and a culture of cleanliness. Factors of adherence to waste collection regulations were found to be public knowledge, social acceptability, convenience and perception of importance. The collection system was assessed by rational-intuitive consideration of all indicators and principles, to be mostly acceptable from an ISWM framework due to: a high collection rate (~100% daily) which is enabled by effective monitoring and efficient operation; a high participation rate; similarity of the resource recovery rate to that of other developing and developed countries; and long-term affordability. Areas for improvement in equality of service provision, collaboration with informal collectors, and communication were identified. Lessons learned about communal container collection are applicable to lower-middle and upper-middle income countries.

Distributed stream-based applications manage large quantities of data and exhibit unique production and consumption patterns that set them apart from general-purpose applications. This dissertation examines possible ways of creating more efficient memory management schemes. Specifically, it looks at the memory reclamation problem. It takes advantage of special traits of streaming applications to extend the definition of the garbage collection problem for those applications and include not only data items that are not reachable but also items that have no effect on the final outcome of the application. Streaming applications typically fully process only a portion of the data, and resources directed towards the remaining data items (i.e., those that dont affect the final outcome) can be viewed as wasted resources that should be minimized. Two complementary approaches are suggested: 1. Garbage Identification 2. Adaptive Resource Utilization Garbage Identification is concerned with an analysis of dynamic data dependencies to infer those items that the application is no longer going to access. Several garbage identification algorithms are examined. Each one of the algorithms uses a set of application properties (possibly distinct from one another) to reduce the memory consumption of the application. The performance of these garbage identification algorithms is compared to the performance of an ideal garbage collector, using a novel logging/post-mortem analyzer. The results indicate that the algorithms that achieve a low memory footprint (close to that of an ideal garbage collector) perform their garbage identification decisions locally; however, they base these decisions on best-effort global information obtained from other components of the distributed application. The Adaptive Resource Utilization (ARU) algorithm analyzes the dynamic relationships between the production and consumption of data items. It uses this information to infer the capacity of the system to process data items and adjusts data generation accordingly. The ARU algorithm makes local capacity decisions based on best-effort global information. This algorithm is found to be as effective as the most successful garbage identification algorithm in reducing the memory footprint of stream-based applications, thus confirming the observation that using best-effort global information to perform local decisions is fundamental in reducing memory consumption for stream-based applications.

In the past years solid state disks have developed drastically and are now gaining increased popularity compared to conventional hard drives. While hard disk drives work predictable, transparent SSD routines work in the background without the user’s knowledge. This work describes the changes to the everyday life for forensic specialists; a forensic investigation includes data recovery and the gathering of a digital image of each acquired memory that provides proof of integrity through a checksum. Due to the internal routines, which cannot be stopped, checksums are falsified. Therefore the images cannot prove integrity of evidence anymore. The report proves the inconsistence of checksums of SSD and shows the differences in data recovery through high recovery rates on hard disk drives while SSD drives scored no recovery or very poor rates.

The design of a waste collection system affects public health, the extent of participation in the system by residents, the recovery of resources from waste, and the cost of collection. Many developing countries use communal container collection [CCC] systems in which large containers are dispersed throughout neighbourhoods for the storage of waste until collection. These systems tend to have limited success as they often do not garner viable amounts of participation and containers are prone to being overfilled. The communal container waste collection system in the city of Aguascalientes, AGS, Mexico was assessed according to the Integrated Solid Waste Management [ISWM] principles of social acceptability, environmental effectiveness, economic affordability and effective management. Information was collected through seven interviews with waste-related managers, 282 residential questionnaires, and 12 informal collector questionnaires. The collection system garners a high participation rate (99%) attributed to: non-burdensome one-way distances from residences to containers (mean 114+/-71m); thorough, daily collection; and a culture of cleanliness. Factors of adherence to waste collection regulations were found to be public knowledge, social acceptability, convenience and perception of importance. The collection system was assessed by rational-intuitive consideration of all indicators and principles, to be mostly acceptable from an ISWM framework due to: a high collection rate (~100% daily) which is enabled by effective monitoring and efficient operation; a high participation rate; similarity of the resource recovery rate to that of other developing and developed countries; and long-term affordability. Areas for improvement in equality of service provision, collaboration with informal collectors, and communication were identified. Lessons learned about communal container collection are applicable to lower-middle and upper-middle income countries.

Submitted by Noeme Timbo (noeme.timbo@metodista.br) on 2018-03-05T19:34:17Z No. of bitstreams: 1 Andreiza Dantas.pdf: 767550 bytes, checksum: a7b7f8d0112aa8c2aedb9b5ec9696fa1 (MD5) / Made available in DSpace on 2018-03-05T19:34:17Z (GMT). No. of bitstreams: 1 Andreiza Dantas.pdf: 767550 bytes, checksum: a7b7f8d0112aa8c2aedb9b5ec9696fa1 (MD5) Previous issue date: 2017-08-31 / One of the main problems of today's society is the high production of urban waste. The main cities of Brazil find it difficult to dispose of this material in the soil. Thus, the present study had as objectives: to investigate the practice of selective garbage collection, its difficulties, benefits and improvements, and check what the consumer does with the garbage, study the collectors, the city of São Bernardo do Campo, and the conditions of reuse of what was collected by them, because there are materials that do not have a market for recycling. For this, the concepts of Brandalise et al. (2014) due to environmental education, Bernardo and Ramos (2016) due to the selective collection, Demajorovic et al. (2014) due to the reverse logistics, Baptista (2015) due to the cooperative of collectors. As for the method for the elaboration of this work, a quantitative approach was adopted, based on the theory of Godoi et al. (2010), the data were obtained through semi-structured interviews, 8 interviewees were interviewed, 4 interviewees have a direct relationship with the recycling chain, and 4 interviewees, who are consumers, who have no relation to the chain in question. It was found in the study that there is an indication that the level of consciousness needs to increase, although people know the existence and importance of garbage collection, the practice does not always match what people say about being aware and knowledge about the existence of the law that deals with this. Another piece of information relates to the public power, which needs to act with more expression and commitment to the environment, due to the manipulation of information and knowledge that can cause an increase in environmental awareness in society, on the structuring of the city to receive And to work selective collection of garbage, regarding the application of the PNRS law, as a form of prevention of natural resources, To be proactive in the activities of collectors' cooperatives in relation to private sector companies, there is a high concern with the production of waste versus what is collected for recycling, it is also concerned with the destination and the return of this material to the productive chain. That the law may charge applications of responsibilities and punish possible noncompliance regarding the environmental context. However, the more one invests in the prevention of environmental resources, the smaller the occurrences to public health. / Um dos principais problemas da sociedade atual é a alta produção de lixo urbano. As principais cidades do Brasil encontram dificuldades para dispor esse material no solo. Dessa forma, o presente estudo teve como objetivos: investigar a prática da coleta seletiva de lixo, suas dificuldades, benefícios e melhorias, assim como verificar o que o consumidor faz com o lixo, estudar os catadores, a prefeitura de São Bernardo do Campo e as condições de reaproveitamento do que foi coletado por eles, em razão de haver materiais que não possuem mercado para a reciclagem. Para tanto, foram utilizados os conceitos de Brandalise et al. (2014) em função da educação ambiental, Bernardo e Ramos (2016) em função da coleta seletiva, Demajorovic et al. (2014) em função da logística reversa, Baptista (2015) em função da cooperativa de catadores. Quanto ao método para a elaboração desse trabalho foi assumida uma abordagem qualitativa, com base na teoria de Godoi et al. (2010), os dados foram obtidos por meio de entrevistas semiestruturadas, foram oito pessoas entrevistadas, sendo que quatro entrevistados possuem relação direta com a cadeia produtiva da reciclagem e os outros quatro entrevistados são consumidores, que não possuem relação com a cadeia em questão. Constatou-se no estudo que há indicação que o nível de consciência precisa aumentar, embora as pessoas saibam da existência e da importância da coleta de lixo, a prática nem sempre condiz com o que as pessoas dizem de ter consciência e conhecimento sobre a existência da lei que trata disso. Outro dado apurado diz respeito ao poder público, que precisa atuar com mais expressão e compromisso com o meio ambiente, em virtude da manipulação da informação e do conhecimento que podem causar um aumento na conscientização ambiental na sociedade, sobre a estruturação da cidade para receber e trabalhar a coleta seletiva de lixo, quanto à aplicação da lei da PNRS, como forma de prevenção dos recursos naturais, ser proativo na atuação das cooperativas de catadores em relação às empresas do setor privado. Existe uma alta preocupação com a produção de lixo versus o que é recolhido para a reciclagem, preocupa-se também com a destinação e o retorno desse material para a cadeia produtiva, que a lei possa cobrar aplicações de responsabilidades e punir possíveis descumprimentos referentes ao contexto ambiental. Contudo, quanto mais se investe na prevenção dos recursos ambientais, menores serão as ocorrências à saúde pública.

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