Orientador: Jose Antonio Siqueira Dias / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-09T20:31:51Z (GMT). No. of bitstreams: 1 Tozetto_EduardoHenrique_M.pdf: 2634313 bytes, checksum: 16d70c7f88dab18e657af6ec34a2defb (MD5) Previous issue date: 2007 / Resumo: O contexto econômico competitivo em que as empresas que desenvolvem ferramentas para projeto de CIs estão inseridas dificulta o estabelecimento de padrões e plataformas de desenvolvimento comuns. Em geral, a necessidade de inúmeras ferramentas resulta em um ambiente de projeto fragmentado. Este trabalho apresenta uma ferramenta desenvolvida através da implementação de interfaces gráficas paramétricas em TCL/TK, que integra funções gerais, permitindo a rápida codificação de procedimentos e seu acesso através de elementos gráficos. A ferramenta desenvolvida serve para facilitar e otimizar as tarefas envolvidas no aprimoramento das técnicas de projeto de Circuitos ntegrados através da elaboração de métodos e scripts visando à automação de etapas do fluxo de projeto / Abstract: The competitive environment in which the companies who develop software tools for the design of integrated circuits creates many barriers to the establishment of standards and common platforms. Usually the need for several software tools leads to a design environment which is fragmented and difficult to manage. This work presents the development of software tool, based on graphical parametric user interfaces in TCL/TK, which integrates many general functions and allows for a quick codification of procedures and its access through the graphics elements. The developed tool optimizes and facilitates the tasks employed in the improvement of the techniques used in integrated circuits design through the elaboration of methods and scripts dedicated to the automation of the design flow steps / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Com a aprovação da Política Nacional de Resíduos Sólidos, a política de sustentabilidade tende ao reaproveitamento de resíduos, em seu ciclo ou destinação final ambientalmente adequada. Neste contexto, são apresentados neste trabalho, estudos do processo de separação de materiais metálicos e não metálicos encontrados em placas de circuito impresso de microcomputadores e a caracterização dos elementos químicos presentes. Para isto efetuou-se a trituração primária (moagem) das placas de circuito impresso, classificação granulométrica, separação de elementos metálicos e não metálicos utilizando separadores, magnético e eletrostático, separação gravimétrica com o uso de clorofórmio e bromofórmio. Para caracterização dos elementos metálicos e não metálicos, foram utilizadas as técnicas de Espectrometria de fluorescência de Raios X e Espectrometria de infravermelho. Os separadores eletrostático e eletromagnético não foram efetivos na separação de placas de circuito impresso para granulometrias inferiores a 9 Mesh. A separação dos elementos metálicos e não metálicos das amostras com granulometrias inferiores a 9 Mesh, teve eficiência parcial utilizando o clorofórmio, mas mostrou-se efetiva com a utilização do bromofórmio. Embora a separação gravimétrica, não tenha sido efetiva, as amostras foram caracterizadas. Para obter uma melhor separação dos elementos presentes na amostra de não metálicos, procedeu-se a trituração secundária (moagem) desta amostra, resultando na desagregação e separação efetiva. / With the approval of the National Solid Waste Policy, the sustainability policy tends to refer to the reuse of waste materials in its cycle or final destination, environmentally right. In this context, it is introduced in this work a study of metallic and nonmetallic materials separation, found in printed circuit boards of microcomputers and present chemical elements characterization. For this purpose it was performed the primary crushing (grinding) of printed circuit boards, particle size classification, separation of metallic and non-metallic elements by using magnetic and electrostatic separators, gravimetric separation using chloroform and bromoform. For characterization of metallic and nonmetallic elements, were used Spectrometry X-ray fluorescence and infrared spectrometry techniques. The electrostatic and electromagnetic separators were not effective in the separation of printed circuit boards for grain sizes below 9 Mesh. The separation of metallic and non-metallic elements of the samples with particle sizes less than 9 Mesh, had partial efficiency using chloroform, but was effective with the use of bromoform. Although the gravimetric separation, has not been effective, the characterized samples were. In order to get better separation of the elements present in non metallic samples it was made the secondary crushing (grinding) of this sample resulting in the breakdown and effective separation.

O avanço da tecnologia de aparelhos eletro-eletrônicos favorece a troca constante dos equipamentos. O freqüente descarte de aparelhos obsoletos se torna um problema de sustentabilidade e também um problema ambiental devido ao seu acúmulo em aterros. A solução para minimizar estes impactos é a reciclagem de seus componentes. Por esta razão, o principal objetivo deste trabalho é estudar o processamento das placas de circuito impresso de telefones celulares através de operações unitárias de Tratamento de Minérios e hidrometalurgia a fim de se recuperar o cobre contido nas placas. Para isso, inicialmente, placas de circuito impresso foram processadas em moinho de martelos, a fim de liberar os materiais, em seguida foi feita a separação magnética do material cominuído. Com a fração não magnética foi feita a separação eletrostática e o material foi separado em: fração condutora, mista e não condutora, com cada fração foi feita a classificação granulométrica e, posteriormente, realizaram-se ensaios de caracterização como pirólise, digestão em água régia e análise química de espectroscopia de emissão óptica por indução de plasma. Os processos hidrometalúrgico aplicados para a recuperação de cobre nas placas de circuito impresso de aparelhos celulares obsoletos envolvem etapas lixiviação com ácido sulfúrico na ausência e na presença de peróxido de hidrogênio. Os resultados da caracterização mostraram que as placas de circuito impresso de celulares após a moagem possuem 24% de cerâmicas; 12,7% de polímeros e 63,3% de metais. Além disso, após a classificação granulométrica e a separação eletrostática os materiais não se concentraram em nenhuma fração especifica, portanto o processamento mecânico visando a recuperação de metais deve contemplar a moagem e a separação magnética. / The technology advancement of electro-electronics devices favors the constant equipment exchange. The frequent disposal of obsolete equipment becomes a sustainability problem and also an environmental problem due to their accumulation in landfills. One possible solution to minimize these impacts is the recycling of their components. For this reason the aim goal of this study is processing of printed circuit boards of mobile phones utilizing unit operation of ore treatment and hydrometallurgy to recover the copper contained in the printed. Therefore, initially printed circuit boards were processed on a hammer mill to release the materials, then it was made magnetic separation of comminuted material. With the non-magnetic fraction was made electrostatic separation in which the material was separated into: conductive, mixed and non-conductive fraction, with each fraction was made grain sized classification and then assays were performed analysis of characterize as pyrolysis, digestion in aqua regia and chemical analysis of inductively coupled plasma atomic emission spectroscopy. Hydrometallurgical processes applied to the cooper recovery in printed circuit boards of obsolete mobile phones, involve steps leaching with sulfuric acid in the absence and presence of hydrogen peroxide. The characterization results showed that the printed circuit boards of mobile phones after grinding have ceramics 24%, polymers 12.7% and metals 63.3%. Moreover, after grain sized classification and electrostatic separation the materials didn\'t concentrate in no specific fraction, therefore the mechanical processing in order to recover metals should include grinding and magnetic separation.

Os resíduos de equipamentos elétricos e eletrônicos é um dos fluxos de resíduos que mais cresce no mundo. O aumento na produção destes equipamentos como resultado dos avanços tecnológicos e a sua rápida obsolescência promovem o aumento de geração deste tipo de resíduos. Portanto, este trabalho tem como objetivo estudar a recuperação de níquel presente no licor de lixiviação de placas de circuito impresso de telefones celulares obsoletos, através da aplicação de processos hidrometalúrgicos e eletrometalúrgico. Inicialmente, foram preparadas soluções sintéticas a partir da composição química do licor de lixiviação das frações magnética (MA) e não magnética (NMA) das placas de circuito impresso cominuídas. Os elementos presentes nas soluções são: ferro, zinco, níquel e alumínio. Posteriormente, foi realizada uma etapa de remoção do ferro, através de precipitação seletiva. A morfologia e a composição química do precipitado foram analisadas através de Microscopia Eletrônica de Varredura (MEV) e EDS, respectivamente. A composição química das soluções resultantes da precipitação foi determinada através da técnica de espectrofotometria de absorção atômica. Através do processo de precipitação conseguiu-se uma porcentagem de remoção de ferro na solução NMA de 99,6% e na solução MA de 99,9%, porém, observou-se também a coprecipitação de zinco, alumínio e níquel. Com as soluções resultantes desta etapa, foi realizada a purificação das soluções através de extração por solvente, utilizando Cyanex 272 como agente extratante. As variáveis estudadas nos ensaios de extração por solvente foram: pH, concentração do extratante, relação fase aquosa/orgânica (A/O) e temperatura. . Além disso, também foi determinado o número de contatos necessários para a extração de ferro, zinco e alumínio, obtendo assim, uma solução aquosa contendo unicamente níquel. Finalmente, foram realizados os ensaios de eletrodeposição para a obtenção de níquel metálico. Foi avaliado o efeito da temperatura sobre o filme depositado. A morfologia dos depósitos e a espessura da camada foram analisadas através do MEV, verificando que o aumento da temperatura influencia nas características do depósito obtido. / Electric and electronic waste (e-waste) is one of the fastest growing waste streams in the world. Continuous increasing production owing to the technological advances and the products consumption rise, all together with the rapid obsolescence of this scrap promotes the necessity of exchange and the increasing of generate waste. Therefore, the aim of this work is to study a recovering of nickel from leach liquor of cell phones printed circuit boards, through of hydrometallurgical and electrometallurgical process application. Firstly, was prepared synthetic solutions of both magnetic (MA) and nonmagnetic (NMA) fractions of printed circuit boards. The metal ions present in the synthetic solutions are: iron, zinc, nickel and aluminium. Afterwards was realized the iron removal stage, through both selective precipitation and solvent extraction process, in order to make a comparison of these techniques. The precipitates were analyzed across of scanning electron microscope (SEM), and the chemical composition of these solutions through atomic absorption spectrometry (AAS). With selective precipitation it was obtained 99,6% and 99,9% of iron removal with selective precipitation in NMA and MA solutions, respectively. Therefore, it was also observed co-precipitation of zinc, aluminium and nickel. With solutions after precipitation stage was carried out the solutions purification through solvent extraction using cyanex 272 as extractant. Solvent extraction test were studied different parameters, such as: equilibrium pH, extractant concentration, aqueous-organic (A/O) ratio and temperature. It was also determinates the stages number required for iron, zinc and aluminium extraction, to obtain nickel in aqueous solution uniquely. Finally, was carried out the electrodeposition test for obtain metallic nickel. Was analyzed the effect of temperature on the deposited layer. Surface Morphology and thickness of the deposits were evaluated by MEV, verifying that temperature increasing influences on deposited layer.

[pt] O objetivo deste trabalho é o desenvolvimento de uma sistemática de análise de dispositivos passivos em parâmetros distribuídos para aplicação em circuitos monolíticos de microondas. O método de análise usado aqui baseia-se no estudo de N- linhas de transmissão aclopadas, através de suas matrizes impedância e de transmissão de tensão e corrente. Essas matrizes sevem como suporte ao estudo dos seguintes elementos: 1 - indutores retangulares multiespiras; 2 - capacitores interdigitais; 3 - MEANDER-LINES; 4 - acopladores de N-portas e 5 - filtros interdigitais do tipo COMB-LINE. Este estudo resultou em um programa de computador que permite analisar estes dibversos elementos. Finalmente, comparações feitas com previsões teóricas de outras análises e com resultados experimentais mostram que os objetivos foram atingidos. / [en] This work is animing at developing a procedure - using distributed parameters - for a systematical analysis of certain passive devices which may be used in Monolithic Microwavw Circuits Here, the analysis is carried out by deriving N-coupled- line matrices, specifically the impedance and current and voltage tranmission ones, for the focused devices. The following circuit elements were then studied: 1 - Rectangular multi-turn inductors; 2 - Interdigital capacitors; 3 - MEANDER-LINES; 4 - N-port couplers; 5 - COMB-LINE interdigital filters. From this work, a computer program has resulted. This program is able to analyze the above mentioned circuit elements. Finaly, the obtained results were compared with those existing in the available literature and also with experimental results. The conclusion is that the analysis method here presented, is able to fairly predict the obtained results.

[pt] Este trabalho propõe uma nova estrutura de rede de interconexão para o sistema de processamento paralelo MULTIPLUS em desenvolvimento no NCE/UFRJ. A rede é tolerante a falhas, e trabalha com chaves de 4 entradas e 4 saídas. Inicialmente, discutem-se as formas de interconexão de máquinas paralelas. Descrevem-se sucintamente algumas arquiteturas de sistemas paralelos com ênfase no MULTIPLUS. A seguir, comentam-se alguns conceitos básicos a respeito de redes de interconexão. Apresenta-se a árvore genealógica das redes de interconexão multiestágio, acompanhada de um breve histórico do surgimento das mesmas. Destacam-se algumas redes de percurso único relacionadas com esta dissertação. Após uma introdução aprofundada sobre tolerância a falhas, descrevem-se algumas redes tolerantes a falhas. Uma análise bem estruturada sobre tolerância a falhas lança as bases para a proposta da rede de interconexão. Introduz-se o subsistema de interconexão do MULTIPLUS, focalizando a estrutura e os tipos de mensagens existentes. Discutem-se vários aspectos relativos à rede proposta, tais como a topologia, o algoritmo e tipo de roteamento e, principalmente, o mecanismo de tolerância a falhas. Descreve-se detalhadamente o projeto do elemento de chaveamento 4x4, com destaque nas máquinas de estado controladoras da chave, porém sem detrimento do circuito de prioridade, do circuito de contagem de pacotes, do circuito de comparação de tamanho da mensagem, do circuito de chaveamento, e do circuito de realinhamento de endereço. Inclui-se também uma descrição detalhada do funcionamento do elemento de chaveamento. Por fim, apresentam-se as expectativas de desempenho de uma rede com 16 entradas e 16 saídas, onde calculam-se o atraso para percorrer a rede de uma mensagem de leitura (12 pacotes), o atraso médio por pacote, o throughput médio por porta, e o throughput médio total da rede. Compara-se o desenho de três redes - uma de tamanho mínimo (4x4), outra de tamanho máximo (256x256), e outra de tamanho 16x16 - implementadas com chaves 2x2 e 4x4. apresentam-se os resultados do projeto, incluindo-se as EPLDs selecionadas, o custo aproximado de uma rede de 256x256 implementada com as referidas EPLDs, e os tempos de compilação dos blocos componentes da chave. Propõe-se a implementação da chave em VLSI, bem como a inclusão da capacidade de comunicação multicast, como futuros desenvolvimentos. / [en] This work proposes a new structure of interconnection network for the MULTIPLUS, a parallel processing system under development at NCE/UFRJ. The network is fault tolerant, and works with 4 inputs and 4 outputs switches. Initially, some interconnection forms of parallel machines are discussed. Some parallel systems architecture are briefly described with emphasis on MULTIPLUS. Following, some basic concepts of interconnection networks are commented. A family tree of multistage interconnection networks, and a short history of their appearance in the literature, are presented. Some Single Path Networks, wich are related with this dissertation, are briefly described. After a deep introduction of fault tolerance, some fault- tolerant interconnection network are described. A well- structured analysis on fault tolerance gives the basis for the interconnection network proposal. The MULTIPLUS interconnection subsystem is introduced, focusing the messages´ types and structure. Various aspects regarding the proposed network - such as the topology, routing type and algorithm and, mainly, the fault- tolerance mechanism - are discussed. The design of the 4x4 switch is described in details, with emphasis on switch controllers finite state machines, but also including the priority circuit, packet counting circuit, message size compariong circuit. A detailed description of the seitch operation is given. At last, the expectede performance of a 16 inputs and 16 outpus network, where a reading message (12 packets) delay, the packet mean delay, port mean throughput, and overall mean throughput are calculated. The performance of 3 networks - one with minimum size (4x4), other with maximum size (256x256), and another with 16x16 size, each of which implemented with 2x2 and 4x4 switches - are compared. The design results are presented, including the selected EPLDs, apprximated cost of a 256x256 network implemented with the already mentioned EPLDs, and the compiling times of the switch blocks. The switch implementation in VLSI tecnology, as well the multicast communication capability, are proposed as future developments.

Dans le domaine du Génie Électrique, la méthode des éléments finis (MEF) associée à une approche pas à pas dans le temps est la plus simple, la plus précise et la plus robuste des méthodes pour modéliser les champs magnétiques dans des dispositifs électromagnétiques en basse fréquence. Néanmoins, cette méthode peut conduire à des temps de calcul extrêmement importants lorsque la constante de temps du système étudié est relativement petite en comparaison de la durée du régime transitoire. C'est dans ce contexte que s'inscrit ces travaux de thèse intitulés « Modélisation numérique par la méthode des éléments finis des systèmes électrotechniques: recherche du régime permanent ». Dans ce manuscrit, une méthode numérique nommée Waveform Relaxation-Newton Method (WR-NM) a été développée. Celle-ci est basée sur la Waveform Relaxation Method (WRM) à laquelle des conditions de périodicité sont appliquées afin d'imposer le régime permanent directement pour des problèmes électromagnétiques couplés à des équations de circuit. La convergence de cette méthode étant similaire à celle d'une méthode point-fixe, elle a été combinée à la méthode de Newton-Raphson dont la convergence est quadratique. Afin de valider et de tester la robustesse de la WR-NM, plusieurs applications sont présentées dans le manuscrit. Des gains importants en temps de calcul sont signifiés en comparaison à l'approche classique et ce pour une précision de la solution identique. Un dernier exemple concernant la modélisation d'une machine à griffes couplés à un pont redresseur montre que la WR-NM peut également être employé dans un cadre industriel. / In electrical engineering, the Finite Element Method (FEM) associated to the time stepping numerical scheme is the most used approach today. This method is simple, accurate and efficient to modeling magnetic fields in low frequency electromagnetic devices. Nevertheless according to the studied cases, the time constant of the device can lead to prohibitive computation time to obtain the steady state. It is in this context that this PhD thesis is written "Numerical modeling by finite element method for electrotechnical systems: steady state investigation". The Waveform Relaxation-Newton Method (WR-NM) was developed, this method is based on the waveform relaxation method (WRM) in which periodicity conditions are applied to impose the steady state for electromagnetic problems coupled to circuit equations. The convergence of this method is similar to a fixed-point method, thus the method is combined to the method of Newton-Raphson whose convergence is quadratic. In order to validate and test the robustness of WR-NM, several applications are presented in the manuscript. Significant gains in computation time are shown in comparison with the conventional approach and for the same precision of the solution. A final example on the modeling of a claw-pole machine coupled to a bridge rectifier shows that the WR-NM can also be employed in an industrial setting.

Abstract The demands toward the development of simple and cost-effective fabrication methods of metallic structures with high lateral resolution on different substrates - applied in many fields of technology, such as in microelectronics, optoelectronics, micromechanics as well as in sensor and actuator applications - gave the idea to perform this research. Due to its simplicity, laser-assisted chemical liquid-phase deposition (LCLD) has been investigated and applied for the metallization of surfaces having practical importance (Si, GaAs, SiO2, Si3N4, etc.) since the beginning of the 80s. By the invention of novel substrates (polyimide, porous silicon), it was adequate to work out new precursors or just adopt old ones and optimise LCLD in order to fabricate metallic micro-patterns upon these materials for various purposes. According to the motivations mentioned above, LCLD was utilized for the fabrication of palladium (Pd) micro-patterns on polyimide (PI), polyimide/copper flexible printed circuit boards (PCBs), fused silica (SiO2) and silicon (Si). The selective metallization of porous silicon (PS) has been carried out with nickel (Ni). Depending on the types of lasers, either the focusing (Ar+ laser beam) or diaphragm projection (KrF and XeCl excimer laser pulses) method was employed. In the course of the work, various precursors of the corresponding metals have been investigated and utilized. In the beginning, the pyrolytic decomposition of palladium-amine complex ions ([Pd(NH3)4]2+) on PI by a scanned and focused Ar+ laser beam was optimised and discussed. Thick (up to several micrometers) and narrow (~ 10 μm) Pd conductor lines with electrical conductivity close to that of the bulk were obtained. In the continuation of these investigations, the precursor was developed further. [Pd(NH3)4]2+ was mixed with the solution of formaldehyde (HCOH) in order to induce the reduction of the metal complex ions. To our knowledge, we were the first - so far - who applied this solution and described the reaction. With the proper choice of the laser parameters, thin Pd films as catalyst layers for electroless copper plating were deposited utilizing Ar+ and excimer lasers as well. The chemically plated copper deposits - upon the obtained Pd film - have excellent electrical and good mechanical properties. In the second part of the thesis, three practical applications (metallization of via holes drilled in PI/Cu flexible PCBs, end-mirror fabrication on single-mode optical fibers, and carbon nanotube growth on Pd activated Si and Si/SiO2 substrates) of Pd LCLD were realized. The previously presented [Pd(NH3)4]2+ and [Pd(NH3)4]2+/HCOH precursors were employed for creating the catalyst Pd layers for the carbon nanotube chemical vapor-phase deposition and for the autocatalytic electroless chemical copper plating, respectively. Finally, a simple novel method was introduced for the area-selective metallization of PS. Since the surface of PS reduces spontaneously most metals from their aqueous solutions, it is difficult to realize localized metal deposition from liquid-phase precursors on it. We proposed the application of a stable Ni plating bath from which the metal deposits only when the PS is irradiated with photons having wavelength shorter than 689 nm, thus making possible an area-selective laser-assisted metal deposition. The deposited metal structures and patterns were analysed by field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectrometer (EDS), by the milling and imaging modes of a focused ion beam system (FIB), optical microscopy, profilometry, resistance, and by reflectance measurements.

Cadmium Telluride (CdTe) is a leading thin film photovoltaic (PV) material due to its near ideal bandgap of 1.45 eV and its high optical absorption coefficient. Advancements in efficiencies of CdTe/CdS solar cells over the past few decades have come from improving the short circuit current (JSC) and Fill Factor (FF) but the Open Circuit Voltage (VOC) has been stagnant. Further improvements in efficiencies should come from increased VOC’s. VOC’s can be improved by increasing the acceptor concentration and minority carrier lifetime. Both these parameters can be controlled by manipulating the native defect concentration in CdTe which can be achieved by varying CdTe stoichiometry. In this study, a deposition system called Elemental Vapor Transport was used to vary the CdTe stoichiometry with an intent to change the native defect concentration and therefore pave way to increase acceptor concentration and lifetimes. Elemental cadmium and tellurium were heated in dedicated zones and their vapors were transported to the substrate using a carrier gas. By varying the temperatures and flowrates of the carrier gas through the zones, the gas phase Cd/Te ratio was varied to deposit Cd-rich, Te-rich and stoichiometric films. Structural properties were investigated using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and Transmission Electron Microscopy (EDS). Electrical characterization of completed devices was carried out by Current-Voltage (J-V), Capacitance-Voltage (C-V), and Spectral Response (SR) and Deep Level Transient Spectroscopy (DLTS) measurements. Cd-rich films showed smaller grain sizes and lesser degree of preferential orientation. Te-rich films showed increased acceptor concentration and carrier lifetimes and solar cells fabricated using these films showed higher VOC’s compared to Cd-rich and stoichiometric films .Higher degree of CdTe-CdS mixing was observed at the interface for films deposited at increased substrate temperatures.

This research study’s premise was to compare and contrast two schools in the Elukwatini area in the Mashishila Circuit in Mpumalanga. One school has a strong culture of learning and teaching, whilst the other school has a weak culture of learning and teaching. The study has endeavoured to find all the similarities and differences in the two schools, in relation to time consciousness and its impact on learning and teaching. This study compares the schools’ cultures with respect to organizational culture, culture of learning and teaching (COLT), school management approaches, how times conscious these schools are and their time management levels. It captures what learners, educators, School Management Teams (SMTs), principals and parents do in relation to time management in the schools. Furthermore, it investigates the roles of all mentioned stakeholders in improving time consciousness, the culture of learning and teaching, effective time management, self-discipline, planning, goal setting, prioritizing, motivation and being responsible. For this research study, data was collected through observations, field notes, interviews and an audio tape. Illumination, understanding and insight of the schools’ time management were achieved in context, by taking the views, facts and ideas of participants into account. Moreover, it will enable school managers to develop programs and policies to alleviate tardiness. The research findings conclusively showed that there was a difference in the cultures of the two schools. In one school the principal, educators and learners were more time conscious, disciplined and concerned about effective learning and teaching. The management approach of the principal and SMT was clearly guiding, motivational and firm. In the other school, however, the principal, educators and learners were less time conscious. They tardily attended classes, there was less concern for learning and teaching, the management approach of the principal was weak, instructions were not taken seriously and a laissez faire approach was prevalent. / Dissertation (MEd (Management Law and Policy Studies))--University of Pretoria, 2007. / Education Management and Policy Studies / MEd / unrestricted