A Virtualização de Funções de Rede (NFV – Network Function Virtualization) é um novo conceito arquitetural que está remodelando a operação de funções de rede (e.g., firewall, gateways e proxies). O conceito principal de NFV consiste em desacoplar a lógica de funções de rede dos dispositivos de hardware especializados e, desta forma, permite a execução de imagens de software sobre hardware de prateleira (COTS – Commercial Off-The-Shelf). NFV tem o potencial para tornar a operação das funções de rede mais flexíveis e econômicas, primordiais em ambientes onde o número de funções implantadas pode chegar facilmente à ordem de centenas. Apesar da intensa atividade de pesquisa na área, o problema de posicionar e encadear funções de rede virtuais (VNF – Virtual Network Functions) de maneira escalável e com baixo custo ainda apresenta uma série de limitações. Mais especificamente, as estratégias existentes na literatura negligenciam o aspecto de encadeamento de VNFs (i.e., objetivam sobretudo o posicionamento), não escalam para o tamanho das infraestruturas NFV (i.e., milhares de nós com capacidade de computação) e, por último, baseiam a qualidade das soluções obtidas em custos operacionais não representativos. Nesta tese, aborda-se o posicionamento e o encadeamento de funções de rede virtualizadas (VNFPC – Virtual Network Function Placement and Chaining) como um problema de otimização no contexto intra- e inter-datacenter. Primeiro, formaliza-se o problema VNFPC e propõe-se um modelo de Programação Linear Inteira (ILP) para resolvêlo. O objetivo consiste em minimizar a alocação de recursos, ao mesmo tempo que atende aos requisitos e restrições de fluxo de rede. Segundo, aborda-se a escalabilidade do problema VNFPC para resolver grandes instâncias do problema (i.e., milhares de nós NFV). Propõe-se um um algoritmo heurístico baseado em fix-and-optimize que incorpora a meta-heurística Variable Neighborhood Search (VNS) para explorar eficientemente o espaço de solução do problema VNFPC. Terceiro, avalia-se as limitações de desempenho e os custos operacionais de estratégias típicas de aprovisionamento ambientes reais de NFV. Com base nos resultados empíricos coletados, propõe-se um modelo analítico que estima com alta precisão os custos operacionais para requisitos de VNFs arbitrários. Quarto, desenvolve-se um mecanismo para a implantação de encadeamentos de VNFs no contexto intra-datacenter. O algoritmo proposto (OCM – Operational Cost Minimization) baseia-se em uma extensão da redução bem conhecida do problema de emparelhamento ponderado (i.e., weighted perfect matching problem) para o problema de fluxo de custo mínimo (i.e., min-cost flow problem) e considera o desempenho das VNFs (e.g., requisitos de CPU), bem como os custos operacionais estimados. Os resultados alcaçados mostram que o modelo ILP proposto para o problema VNFPC reduz em até 25% nos atrasos fim-a-fim (em comparação com os encadeamentos observados nas infra-estruturas tradicionais) com um excesso de provisionamento de recursos aceitável – limitado a 4%. Além disso, os resultados evidenciam que a heurística proposta (baseada em fix-and-optimize) é capaz de encontrar soluções factíveis de alta qualidade de forma eficiente, mesmo em cenários com milhares de VNFs. Além disso, provê-se um melhor entendimento sobre as métricas de desempenho de rede (e.g., vazão, consumo de CPU e capacidade de processamento de pacotes) para as estratégias típicas de implantação de VNFs adotadas infraestruturas NFV. Por último, o algoritmo proposto no contexto intra-datacenter (i.e. OCM) reduz significativamente os custos operacionais quando comparado aos mecanismos de posicionamento típicos uti / Network Function Virtualization (NFV) is a novel concept that is reshaping the middlebox arena, shifting network functions (e.g. firewall, gateways, proxies) from specialized hardware appliances to software images running on commodity hardware. This concept has potential to make network function provision and operation more flexible and cost-effective, paramount in a world where deployed middleboxes may easily reach the order of hundreds. Despite recent research activity in the field, little has been done towards scalable and cost-efficient placement & chaining of virtual network functions (VNFs) – a key feature for the effective success of NFV. More specifically, existing strategies have neglected the chaining aspect of NFV (focusing on efficient placement only), failed to scale to hundreds of network functions and relied on unrealistic operational costs. In this thesis, we approach VNF placement and chaining as an optimization problem in the context of Inter- and Intra-datacenter. First, we formalize the Virtual Network Function Placement and Chaining (VNFPC) problem and propose an Integer Linear Programming (ILP) model to solve it. The goal is to minimize required resource allocation, while meeting network flow requirements and constraints. Then, we address scalability of VNFPC problem to solve large instances (i.e., thousands of NFV nodes) by proposing a fixand- optimize-based heuristic algorithm for tackling it. Our algorithm incorporates a Variable Neighborhood Search (VNS) meta-heuristic, for efficiently exploring the placement and chaining solution space. Further, we assess the performance limitations of typical NFV-based deployments and the incurred operational costs of commodity servers and propose an analytical model that accurately predict the operational costs for arbitrary service chain requirements. Then, we develop a general service chain intra-datacenter deployment mechanism (named OCM – Operational Cost Minimization) that considers both the actual performance of the service chains (e.g., CPU requirements) as well as the operational incurred cost. Our novel algorithm is based on an extension of the well-known reduction from weighted matching to min-cost flow problem. Finally, we tackle the problem of monitoring service chains in NFV-based environments. For that, we introduce the DNM (Distributed Network Monitoring) problem and propose an optimization model to solve it. DNM allows service chain segments to be independently monitored, which allows specialized network monitoring requirements to be met in a efficient and coordinated way. Results show that the proposed ILP model for the VNFPC problem leads to a reduction of up to 25% in end-to-end delays (in comparison to chainings observed in traditional infrastructures) and an acceptable resource over-provisioning limited to 4%. Also, we provide strong evidences that our fix-and-optimize based heuristic is able to find feasible, high-quality solutions efficiently, even in scenarios scaling to thousands of VNFs. Further, we provide indepth insights on network performance metrics (such as throughput, CPU utilization and packet processing) and its current limitations while considering typical deployment strategies. Our OCM algorithm reduces significantly operational costs when compared to the de-facto standard placement mechanisms used in Cloud systems. Last, our DNM model allows finer grained network monitoring with limited overheads. By coordinating the placement of monitoring sinks and the forwarding of network monitoring traffic, DNM can reduce the number of monitoring sinks and the network resource consumption (54% lower than a traditional method).

This dissertation presents a pumping system operation efficiency improvement solution that includes optimal selection and control of the water pump. This solution is formulated based on the performance, operation, equipment and technology (POET) framework. The focus is on the minimization of the operational energy cost. This efficiency improvement solution is divided into three stages in accordance with the operation category of the POET framework. The first stage is to select the optimal pump capacity by considering both energy efficiency and load shifting requirements. The second stage is to develop a flexible pump controlling strategy that combines and balances the contributions from energy efficiency and load shifting. The last stage is to improve the robustness of the control system using the closed-loop model predictive control approach. An optimal pump capacity selection model is formulated. In this model, additional capacity requirements for load shifting are considered along with the traditional energy efficiency requirements. By balancing the contributions from load shifting and energy efficiency, the operational energy cost can be reduced by up to 37%. An optimal pump control is formulated. The objective of this control model is to balance the energy efficiency and load shifting contributions during the operation and minimize the operational energy cost. This control model is tested under different operational conditions and it is compared to other existing control strategies. The simulation and comparison results show that the proposed control strategy achieves the lowest operational energy cost in comparison to other strategies. This optimal pump control model is further modified into the closed-loop model predictive control format to increase the robustness of the control system under operation uncertainties. A mixed integer particle swarm optimization algorithms is employed to solve the optimization problems in this research. AFRIKAANS : Hierdie verhandeling bied ’n verbeterde oplossing vir die operasionele doeltreffendheid van pompstelsels wat die optimale keuse en beheer van die waterpomp insluit. Hierdie oplossing is geformuleer op ’n raamwerk wat werkverrigting, bedryf, toerusting en tegnologie in ag neem. Die oplossing fokus op die vermindering van bedryfsenergie koste. Hierdie oplossing is onderverdeel in drie fases soos bepaal deur die bedryfskategorie gegrond op die bogenoemde raamwerk: Die eerste fase is die keuse van die optimale pompkapasiteit deur beide energiedoeltreffendheid en lasverskuiwing in ag te neem. Die tweede fase is om ’n buigbare pompbeheer strategie te ontwikkel wat ’n goeie balans handhaaf tussen die onderskeie bydraes van energiedoeltreffendheid en lasverskuiwing. Die derde fase is om die stabiliteit van die beheerstelsel te verbeter deur gebruik te maak van ’n geslote-lus beheermodel met voorspellende beheer (Predictive Control). ’n Model vir die keuse van optimale pompkapasiteit is geformuleer. In hierdie model word vereistes vir addisionele pompkapasiteit vir lasverskuiwing sowel as vereistes in terme tradisionele energiedoeltreffendheid in ag geneem. Deur die regte verhouding tussen die onderskeie bydraes van energiedoeltreffendheid en lasverskuiwing te vind kan ’n besparing van tot 37% op die energiekoste verkry word. Optimale pompbeheer is geformuleer. Die doel van die beheermodel is om die bydraes van energiedoeltreffendheid en lasverskuiwing te balanseer en om die bedryfsenergie koste te minimiseer. Hierdie beheermodel is getoets onder verskillende bedryfstoestande en dit is vergelyk met ander bestaande beheerstrategiee. Die simulasie en vergelyking van resultate toon dat die voorgestelde beheerstrategie die laagste bedryfsenergie koste behaal in vergelyking met ander strategiee. Hierdie optimale pomp beheermodel is verder aangepas in ’n geslote beheermodel met voorspellende beheerformaat om die stabiliteit van die beheerstelsel te verbeter onder onsekere bedryfstoestande. ’n Gemende heelgetal partikel swerm optimisasie (Mixed interger particle swarm optimization) algoritme is gebruik om die optimiseringsprobleme op te los tydens hierdie navorsingsoefening. / Dissertation (MEng)--University of Pretoria, 2011. / Electrical, Electronic and Computer Engineering / Unrestricted

Energy and environment have become hot topics in the world. The building sector accounts for a high proportion of energy consumption, with over one-third of energy use globally. A variety of optimization methods have been proposed for building energy management, which are mainly divided into two types: model-based and model-free. Model Predictive Control is a model-based method but is not widely adopted by the building industry as it requires too much expertise and time to develop a model. Model-free Deep Reinforcement Learning(DRL) has successful applications in game-playing and robotics control. Therefore, we explored the effectiveness of the DRL algorithms applied to building control and investigated which DRL algorithm performs best. Three DRL algorithms were implemented, namely, Deep Deterministic Policy Gradient(DDPG), Double Deep Q learning(DDQN) and Soft Actor Critic(SAC). We used the building optimization testing (BOPTEST) framework, a standardized virtual testbed, to test the DRL algorithms. The performance is evaluated by two Key Performance Indicators(KPIs): thermal discomfort and operational cost. The results show that the DDPG agent performs best, and outperforms the baseline with the saving of thermal discomfort by 91.5% and 18.3%, and the saving of the operational cost by 11.0% and 14.6% during the peak and typical heating periods, respectively. DDQN and SAC agents do not show a clear advantage of performance over the baseline. This research highlights the excellent control performance of the DDPG agent, suggesting that the application of DRL in building control can achieve a better performance than the conventional control method. / Energi och miljö blir heta ämnen i världen. Byggsektorn står för en hög andel av energiförbrukningen, med över en tredjedel av energianvändningen globalt. En mängd olika optimeringsmetoder har föreslagits för Building Energy Management, vilka huvudsakligen är uppdelade i två typer: modellbaserade och modellfria. Model Predictive Control är en modellbaserad metod men är inte allmänt antagen av byggbranschen eftersom det kräver för mycket expertis och tid för att utveckla en modell. Modellfri Deep Reinforcement Learning (DRL) har framgångsrika tillämpningar inom spel och robotstyrning. Därför undersökte vi effektiviteten av DRL-algoritmerna som tillämpas på byggnadskontroll och undersökte vilken DRL-algoritm som presterar bäst. Tre DRL-algoritmer implementerades, nämligen Deep Deterministic Policy Gradient (DDPG), Double Deep Q Learning (DDQN) och Soft Actor Critic (SAC). Vi använde ramverket Building Optimization Testing (BOPTEST), en standardiserad virtuell testbädd, för att testa DRL-algoritmerna. Prestandan utvärderas av två Key Performance Indicators (KPIs): termiskt obehag och driftskostnad. Resultaten visar att DDPG-medlet presterar bäst och överträffar baslinjen med besparingen av termiskt obehag med 91.5% och 18.3%, och besparingen av driftskostnaden med 11.0% och 14.6% under topp och typisk uppvärmning perioder, respektive. DDQN- och SAC-agenter visar inte en klar fördel i prestanda jämfört med baslinjen. Denna forskning belyser DDPG-medlets utmärkta prestanda, vilket tyder på att tillämpningen av DRL i byggnadskontroll kan uppnå bättre prestanda än den konventionella metoden.

Police expenditure has a direct effect on the efforts of the police to prevent and investigate crime. It also contributes a lot to run various programs used to enhance public awareness of crime to affect the national development of the country. This doctoral study aims at investigating the relationship between police expenditure and crime in the context of Tigray Regional State of Ethiopia. The study is a qualitative study by design. Data pertinent to the study were gathered through interview schedule, which was prepared first in Tigrigna and translated into English later, given to relevant sets of two groups of participants, namely zone and district participants referred hereunder as sample A and Sample B, respectively. Participants of the study have been selected purposively. Data generated from the interview schedule were analysed subject to thematic analysis. Major findings of the study indicate that budget allocation is mainly made on the basis of police functions and activities; many of the workers in police are not aware of the national guideline in planning and preparing budgets, and believe that the national security situation predominantly determines the budget allocation rather than the standards set in the country. A considerable number of the police staff are not aware of the procedures in formulating the budget. They agreed that even though there are clear strategies to prevent and investigate crimes, they are not fully implemented. However, they consensually agreed that priority should be given to crime prevention in allocating budget to police. It further discusses the community participation in raising funds through the community policing program is high, and the aim is to strengthen the police to effectively discharge its responsibilities in maintaining social order and safeguarding the people from crime and crime-related problems. Major recommendations include improving the budget, which is mandatory, and enhancing the community and police partnership is essential. It is also necessary to give much attention to enhance the institutional capacity of police to address community problems adequately through installing various police technologies to which budget improvement is mandatory. The input of the study is finally useful to policymakers to look at the police expenditure and bring their attention into the procedures to avoid budget scarcity apparent in the police institutions not only in the region but also across the country. It helps the police develop various programs inactive due to a shortage in the budget. / ፅሟቕ ወፃኢታት ፖሊስ ኣብ ምክልኻልን ምርመራን ገበን ኣብ ዝግበር ፃዕሪ ብቀጥታ ፅልዋ አለዎም፡፡ ከምኡ ውን ኣብ ብሄራዊ ዕብየት ሀገር ናይ ባዕሉ ብፅሒት እንትህልዎ ፖሊስ ኣብቲ ዕብየት እኹል ግንዛበ ክህልዎን ዝወፁ መደባት ብኣግባቡ ክፍፀሙን አቶም ወፃኢታት ዓብይ ረብሓ ኣለዎም፡፡ በዚ ምኽንያት ውን እዚ ናይ ዶክትሬት ድግሪ መፅናዕቲ ኣብ ሞንጎ ወፃኢታት ፖሊስ ብሄራዊ ክልላዊ መንግስቲ ትግራይን ኣብታ ክልል ዝፍፀም ገበንን እንታይ ዓይነት ርክብ ኣለዎም ኣብ ዝብል ርእሲ ዘድህብ እዩ፡፡ ንድፊ ወይም ዲዛይን ናይቲ መፅናዕቲ ንባባዊ /ኳሊታቲቭ/ እንትኾን እቶም ናይ መፅናዕቲ ሓበሬታት ብቃለ መሕትትን ፅሑፍ መሕትትን ተዳልዮም በቶም ናይ ተሳተፍቲ ቋንቋ ዝኾነ ትግርኛ ተቶርጊሙ ናብ ተሳተፍቲ ተበቲኑ እዩ፡፡ ምስተኣከበ ውን እንደገና ናብ እግሊዝኛ ተተርጊሙ እዩ፡፡ እቶም ዝነበሩ ተሳተፍቲ ኣብ ዞባን ወረዳን ኮይኖም ናሙና Aን ናሙና Bን ተባሂሎም ኣብ 2ተ ጉጅለ ተኸፊሎም እዮም፡፡ ኣመራርፃ ናይቶም ተሳተፍቲ ምኽንያታዊ ወይ ከዓ ይፈልጡ እዮም ዝብል እንትኾን አቲ ዝተኣከበ ሓበሬታ (ቃለ መሕትትን ፅሑፍ መሕትትን) ጭብጡ ብምዝርዛር እቲ ዝተኣከበ ሓበሬታ ተተንቲኑ እዩ፡፡ ዋና ናይቲ መፅናዕቲ ርካቦት ከምዝሕብሮ ንፖሊስ ተባሂሉ ዝብጀት በጀት መበገሲኡ ፖሊስ ንዝሰርሖምን ዝነጥፎምን ነገራት ዘማእኸለ እዩ፡፡ ኮይኑ ግና መብዛሕቲኦም ኣባላት ፖሊስ በጀት ከመይ ከምዝብጀትን ከመይ ከምዝዳለውን ኣብ ዝግለፅ መብርሂ እኹል ዝኾነ ፍልጠት የብሎምን፡፡ በቲ ናይ ፖሊስ ስታንዳርድ እንተይኮነስ በጀት ዝብጀት በቲ ቢሮ ፀጥታን ምምሕዳርን ዘውፅኦ መምርሒ መሰረት እዩ ኢሎም ይኣምኑ፡፡ ከምኡውን ብዙሓት ፖሊሳት ንበጀት መበጀቲ ቀመር ከመይ ከምዝዳለው ኣይፈልጥዎን፡፡ ብመዳይ ምክልኻልን ምፅራይን ገበን እውን ግልፂ ዝኾነ መምርሒን መሳርሒን ዋላ ኳ እንተሃለወ ኣብ ኣፈፃፅሙኡ ጉድለት ይረኣይ እዩ፡፡ በዚ ውን ኩሎም ተሳተፍቲ ከምዘስማዕምዑሉ ንምክልኻልገበን ዝለዓለ በጀት ክብጀተሉ ኣለዎ ኢሎም፡፡ ተሳትፎ ማሕበረሰብ ኣብ ፖሊስ ኮሚኒቲ መደባት ዝለዓለ እንትኸውን በዚ ውን ዕላማ ፖሊስ ኮሚኒቲ ሽትኡ ክወቅዕ ገይርዎ እዩ፡፡ እዙይ ብምህላው ውን ፖሊስ ዋርድያ ህዝቢ ኮይኑ ካብ ገበንን ስግኣት ገበንን ህዝቢ ነፃ ክኾኑ ሓላፍነት ወሲዱ በርቲዑ ንክሰርሕ ሓጊዙዎ እዩ፡፡ ብመዳይ ፅንዓት መቅረቢ እንትድህስስ ንፖሊስ ስራሕቲ ዝለዓለ በጀት ከምዘደልዮን እዚ ውን ፖሊስን ማሕበረሰብን ሓቢሮም ክሰርሑ ኣብ ምግባር ዕዙዝ ተራ ኣለዎ፡፡ ዓቅሚ ፖሊስ ንምዕባይ ኣብ ዝግበር ፃዕሪ እኹል ቆላሕታ ክወሃብ ኣለዎ ፣ ምክንያቱ ‘ውን ዘመኑ ዝጠልቦ ቴክኖሎጂ ንምዕባይ በጀት ወሳኒ እዩ፡፡ እዚ መፅናዕቲ ንፖሊሲ መውፃእቲ ውን ዓብይ ረብሓ እንትህልዎ ንናይ ፖሊስ በጀት ቆላሕታ ክህቡን ዋሐዲ በጀት ፖሊስ ኣብ ምዕባይን ከም ግብኣት ይጠቕሞም እዩ፡፡ እዚ ፀገም ውን ኣብ ትግራይ ክልል ንዘሎ ጥራሕ እንተይኾነስ ኣብ መላእ እታ ሃገር ንዘሎ ፀገም ክፈትሕ ይኽእል እዩ ተባሂሉ ተፀኒዑ ኣሎ፡፡ በዚ ውን ብሰንኪ ሕፅረት በጀት ንዝጎድል ስራሕቲ ፖሊስ ብእዋኑ ክማላእን ክብ ክብልን ዓብይ ጥቅሚ ኣለዎ፡፡ / Police Practice / D. Litt. et Phil. (Police Science)