Academic literature on the topic 'C. 626 – 682)'

Submitted by Kilvya Braga (kilvyabraga@hotmail.com) on 2018-05-14T14:15:46Z No. of bitstreams: 1 Flavio Medeiros - Tese.pdf: 4026286 bytes, checksum: b8f88ed9bff48d2f4eed7e9d7039c5ba (MD5)<br>Made available in DSpace on 2018-05-14T14:15:46Z (GMT). No. of bitstreams: 1 Flavio Medeiros - Tese.pdf: 4026286 bytes, checksum: b8f88ed9bff48d2f4eed7e9d7039c5ba (MD5) Previous issue date: 2016<br>Desde os anos 70, o pré-processador C é amplamente utilizado na prática para adaptar sistemas para diferentes plataformas e cenários de aplicação. Na academia, no entanto, o pré-processador tem recebido fortes críticas desde o início dos anos 90. Os pesquisadores têm criticado a sua falta de modularidade, a sua propensão para introduzir erros sutis e sua ofuscação do código fonte. Para entender melhor os problemas de usar o pré-processador C,considerando a percepção dos desenvolvedores, realizamos 40 entrevistas e uma pesquisa entre 202 desenvolvedores. Descobrimos que os desenvolvedores lidam com três problemas comuns na prática: erros relacionados à configuração, testes combinatórios e compreensão do código. Os desenvolvedores agravam estes problemas ao usar diretivas não disciplinadas, as quais não respeitam a estrutura sintática do código. Para evoluir famílias de programas de forma segura, foram propostas duas estratégias para a detecção de erros relacionados à configuração e um conjunto de 14 refatoramentos para remover diretivas não disciplinadas. Para lidar melhor com a grande quantidade de configurações do código fonte, a primeira estratégia considera todo o conjunto de configurações do código fonte e a segunda estratégia utiliza amostragem. Para propor um algoritmo de amostragem adequado, foram comparados 10 algoritmos com relação ao esforço (número de configurações para testar) e capacidade de detecção de erros (número de erros detectados nas configurações da amostra). Com base nos resultados deste estudo, foi proposto um algoritmo de amostragem. Estudos empíricos foram realizados usando 40 sistemas C do mundo real. Detectamos 128 erros relacionados à configuração, enviamos 43 correções para erros ainda não corrigidos e os desenvolvedores aceitaram 65% das correções. Os resultados de nossa pesquisa mostram que a maioria dos desenvolvedores preferem usar a versão refatorada,ou seja,disciplinada do código fonte,ao invés do código original com as diretivas não disciplinadas. Além disso,os desenvolvedores aceitaram 21 (75%) das 28 sugestões enviadas para transformar diretivas não disciplinadas em disciplinadas. Nossa pesquisa apresenta resultados úteis para desenvolvedores de código C durante suas tarefas de desenvolvimento, contribuindo para minimizar o número de erros relacionados à configuração, melhorar a compreensão e a manutenção do código fonte e orientar os desenvolvedores para realizar testes combinatórios.<br>Since the 70s, the C preprocessor is still widely used in practice in a numbers of projects, including Apache,Linux ,and Libssh, totail or systems to different platforms and application scenarios. In academia,however, the preprocess or has received strong critic is msinceatl east the early 90s. Researchers have criticized its lack of separation of concerns, its proneness to introduce subtle errors, and its obfuscation of the source code. To better understand the problems of using the C preprocessor, taking the perception of developers into account, we conducted 40 interviewsandasurveyamong 202 developers. We found that developers deal with three common problems in practice: configuration-related bugs, combinatorial testing, and code comprehension. Developers aggravate these problems when using undisciplined directives (i.e., bad smells regarding preprocessor use), which are preprocessor directives thatdo notrespect thesyntactic structureof thesource code. To safely evolve preprocessor based program families, we proposed strategies to detect configuration-relatedbugs and bad smells, and a set of 14 refactorings to remove bad smells. To better deal with exponential configuration spaces, our strategies uses variability-aware analysis that considers the entire set of possible configurations, and sampling, which allows to reuse C tools that consider only one configuration at a time to detect bugs. To propose a suitable sampling algorithm, we compared 10 algorithms with respect to effort (i.e., number of configurations to test) andbug-detection capabilities (i.e.,numberofbugs detected in the sampled configurations). Based on the results, we proposed a sampling algorithm with an useful balance between effort and bug-detection capability. We performed empirical studies using a corpus of 40 C real-world systems. We detected 128 configuration-related bugs, submitted 43 patches to fix bugs not fixed yet, and developers accepted 65% of the patches. The results of our survey show that most developers prefer to use the refactored (i.e., disciplined) version of the code instead of the original code with undisciplined directives. Furthermore, developers accepted 21 (75%) out of 28 patches submitted to refactor undisciplined into disciplined directives. Our work presents useful findings for C developers during their development tasks, contributing to minimize the chances of introducing configuration-related bugs and bad smells, improve code comprehension, and guide developers to perform combinatorial testing.

Nonylphenol ethoxylates (NPEO) are commercially available non-ionic surfactants that, along with the parent nonylphenol (NP), are considered to be possible endocrine disrupters. NP and NPEO are resistant to conventional aerobic biological water treatment systems. Alternatives to this technology are sought to remove these and other bio-resistant compounds from wastewaters. Composites of the photocatalyst, TiOi, and activated carbon (AC) adsorbents have been prepared, characterised and applied as adsorbents and photocatalysts in removal of phenols and NPEO from aqueous solution. Two methods were utilised to prepare of TiO2/C composites. AC was coated with TiO2 derived from the hydrolysis of Ti(OPr')4, and with Degussa P25 using a polyvinyl alcohol binder that was subsequently carbonised in an inert atmosphere. The TiO2/C composites were characterised by nitrogen adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible reflectance spectroscopy and scanning electron microscopy. The AC and TiO2/C adsorption capacity for phenol was observed to be affected by the surface area and surface chemistry of the adsorbent, as well as the pH of solution. The NPEO adsorption capacity and rate of adsorption was found to be dependant on the pore size distribution of the adsorbent. The effect of surface chemistry and solution pH was minimal. The selectivity of the adsorbent in the adsorption of NPEO was studied using HPLC. The rate of photooxidation of phenol was found to be first-order and greatest under basic conditions. This is attributed to changes in the electronic structure of the TiO2 under these conditions that increases the rate of reduction of molecular oxygen, often considered to be the rate limiting step. Photodegradation of NPEO led to the aggregation and sedimentation of TiOz particles. HPLC and GC-MS analysis identified photomineralisation intermediates and the mechanism of photodegradation of NPEO is discussed.