In South Africa, as much as 33 million tons of ash, a waste product of burning coal, are produced per year. Of the total ash produced, just over 8% is sold for utilisation, the remainder of which is disposed of in landfills or ash lagoons. Countries like the UK, USA, Germany, Poland and Russia are producing Lightweight Aggregates (LWAs) commercially by using fly ash and clay, however, this technology is not available in many developing countries. The opportunity to utilise the fly ash produced in South Africa for the production of coarse LWA for use in structural concrete has therefore been identified and investigated in this dissertation. This dissertation consists of two phases, firstly to determine a suitable method for the manufacture of a high quality LWA, and secondly to determine the manufactured aggregate’s performance and potential for use in structural concrete. In the first phase, different LWA batches were produced using fly ash as the main constituent and kaolin clay, in contents of 0%, 10%, 20% and 30% by mass, as a binder. Green aggregate particles were produced in a disc granulator and then hardened using sintering at 1200°C for one hour. It was found that the LWA batch containing 20% kaolin produced LWA with the most suitable mechanical properties for use in concrete, and was therefore mass produced for further aggregate testing and for the production of concrete specimens for concrete testing. The final LWA produced was found to have an apparent density of 1600 kg/m3 and 24 hour water absorption of 12% by mass. The produced LWA was also found to have an Aggregate Crushing Value (ACV) and 10% FACT of 24.4% and 185 kN, respectively, which indicated that it would be suitable for use in High Strength Concrete (HSC). The sintering process was found to induce liquid phase sintering and the formation of new phases, mainly mullite, which contributed to the relatively high strengths of the aggregates. In the second phase of this dissertation, the manufactured LWA was then used to produce HSC and Normal Strength Concrete (NSC) specimens for concrete testing, which were compared to control mixes made with normal weight dolomite aggregate. In the HSC testing, concrete with a density of 2300 kg/m3 and compressive strength of 90 MPa was produced with the LWA. In HSC, it was found that internal curing was improved when up to 50% of the normal weight coarse aggregate was replaced by saturated LWA for this specific concrete mix. By using different stiffness relationship models between the concrete constituents, it was found that the manufactured LWA modulus of elasticity was between 8-23 GPa, and had a compressive strength of between 49-60 MPa. The Interface Transition Zone (ITZ) in concrete produced with the LWA was found to be stronger than the LWA as a result of the impregnation of the cement paste within the aggregate, and that the LWA was reactive in an alkaline environment. This resulted in an improved early age strength development, as well as caused the concrete failure surface to occur through the LWA particles rather than at the ITZ. Finally, Lightweight Concrete (LWC), having a dry density below 2000 kg/m3, was produced with the manufactured LWA. The LWC, produced with a water-to-cement ratio of 0.75, 28 day compressive strength of 24 MPa, modulus of elasticity of 21 GPa and dry density of 1800 kg/m3, was found to be suitable for use as structural concrete when assessed in terms of EN 1992-1-1 (2004). / Dissertation (MEng (Structural Engineering))--University of Pretoria, 2020. / Civil Engineering / MEng (Structural Engineering) / Restricted

Este trabalho tem por objetivo o estudo de concretos leves com agregados inovadores de argila vermelha calcinada e subprodutos agroindustriais. A argila utilizada na pesquisa foi caracterizada por meio das técnicas de limites de liquidez (LL) e plasticidade (LP), análise granulométrica, análise química e difração de raios X (DRX). Foram confeccionados corpos de prova de argila vermelha calcinada com incorporações de serragem de madeira, cinza do bagaço da cana-de-açúcar e silicato de sódio. Os corpos de prova de argila vermelha calcinada, queimados à temperatura de 900 °C, foram caracterizados por meio da avaliação da retração linear, absorção de água, porosidade aparente, massa específica aparente, expansão por umidade e resistência à compressão. Após a caracterização dos corpos de prova de argila vermelha calcinada, foram produzidos dois tipos de agregados, sendo o primeiro composto por 57% de argila e 43% de cinza do bagaço de cana-de-açúcar, conformados com água e silicato de sódio (proporção 1:1), e o segundo composto por 70% de argila e 30% de serragem de madeira. Os corpos de prova de concreto leve foram caracterizados pelos ensaios de slump, massa específica fresca, resistência à compressão, módulo de deformação, retração por secagem, absorção de água, índice de vazios e massa específica aparente e condutividade térmica. Os resultados desta pesquisa indicam a viabilidade da produção de agregados leves de argila vermelha calcinada com incorporações de subprodutos agroindustriais para utilização em concretos, uma vez que, mesmo com grande quantidade de utilização de subprodutos agroindustriais na produção dos agregados leves, os concretos produzidos com esses agregados apresentaram características similares aos concretos produzidos com agregados comerciais, apresentando um ganho econômico e energético significativo. / This paper aims to study lightweight concrete with innovative calcined clay lightweight aggregates made with agro-industrial by-products. The clay used in this research was characterized by techniques of liquid and plastic limits, particle size analysis, chemical analysis and X-ray diffraction (XRD). Calcined clay specimens were made with incorporations of wood sawdust, sugar cane ash and sodium silicate. These specimens, burned at a temperature of 900°C, were characterized by evaluating of linear shrinkage, water absorption, apparent porosity, specific mass, moisture expansion and compressive strength. After characterization of calcined clay specimens, two types of calcined clay lightweight aggregates with agro-industrial by-products were produced, wherein the first made with 57% of clay and 43% of sugar cane ash, mixed with water and sodium silicate (proportion 1:1) and the second made with 70% clay and 30% wood sawdust, mixed with water and burned at 900 °C. Specimens of lightweight concrete were characterized by slump test, fresh specific mass, compressive strength, modulus of elasticity, water absorption, voids and bulk density and thermal conductivity. Results of this research indicates the viability to produce calcined clay lightweight aggregates made with agro-industrial by-products to use in concrete, even using large amount of agro-industrial by-products, once concretes made with lightweight aggregates with agro-industrial by-products presented similar characteristics than those made with commercial aggregates, presenting significant energetic gain.

Este trabalho tem por objetivo o estudo de concretos leves com agregados inovadores de argila vermelha calcinada e subprodutos agroindustriais. A argila utilizada na pesquisa foi caracterizada por meio das técnicas de limites de liquidez (LL) e plasticidade (LP), análise granulométrica, análise química e difração de raios X (DRX). Foram confeccionados corpos de prova de argila vermelha calcinada com incorporações de serragem de madeira, cinza do bagaço da cana-de-açúcar e silicato de sódio. Os corpos de prova de argila vermelha calcinada, queimados à temperatura de 900 °C, foram caracterizados por meio da avaliação da retração linear, absorção de água, porosidade aparente, massa específica aparente, expansão por umidade e resistência à compressão. Após a caracterização dos corpos de prova de argila vermelha calcinada, foram produzidos dois tipos de agregados, sendo o primeiro composto por 57% de argila e 43% de cinza do bagaço de cana-de-açúcar, conformados com água e silicato de sódio (proporção 1:1), e o segundo composto por 70% de argila e 30% de serragem de madeira. Os corpos de prova de concreto leve foram caracterizados pelos ensaios de slump, massa específica fresca, resistência à compressão, módulo de deformação, retração por secagem, absorção de água, índice de vazios e massa específica aparente e condutividade térmica. Os resultados desta pesquisa indicam a viabilidade da produção de agregados leves de argila vermelha calcinada com incorporações de subprodutos agroindustriais para utilização em concretos, uma vez que, mesmo com grande quantidade de utilização de subprodutos agroindustriais na produção dos agregados leves, os concretos produzidos com esses agregados apresentaram características similares aos concretos produzidos com agregados comerciais, apresentando um ganho econômico e energético significativo. / This paper aims to study lightweight concrete with innovative calcined clay lightweight aggregates made with agro-industrial by-products. The clay used in this research was characterized by techniques of liquid and plastic limits, particle size analysis, chemical analysis and X-ray diffraction (XRD). Calcined clay specimens were made with incorporations of wood sawdust, sugar cane ash and sodium silicate. These specimens, burned at a temperature of 900°C, were characterized by evaluating of linear shrinkage, water absorption, apparent porosity, specific mass, moisture expansion and compressive strength. After characterization of calcined clay specimens, two types of calcined clay lightweight aggregates with agro-industrial by-products were produced, wherein the first made with 57% of clay and 43% of sugar cane ash, mixed with water and sodium silicate (proportion 1:1) and the second made with 70% clay and 30% wood sawdust, mixed with water and burned at 900 °C. Specimens of lightweight concrete were characterized by slump test, fresh specific mass, compressive strength, modulus of elasticity, water absorption, voids and bulk density and thermal conductivity. Results of this research indicates the viability to produce calcined clay lightweight aggregates made with agro-industrial by-products to use in concrete, even using large amount of agro-industrial by-products, once concretes made with lightweight aggregates with agro-industrial by-products presented similar characteristics than those made with commercial aggregates, presenting significant energetic gain.

The use of cellular foam as a core material in light-weight structural applications is of considerable interest. However, advances in this technology have been limited due to the lack of information concerning the macroscopic material behavior of cellular foams. Of particular interest in the design of composite structures is the shear modulus, G, of the core material, which must be established with a high degree of accuracy. Current ASTM test methods for shear modulus determination were researched and found inadequate for testing cellular foam materials. The difficulty in testing foam and the inaccuracies associated with the standard test methods established the need for the development of a test method for these materials. The test method (test fixture and test procedure) developed for cellular foam materials is presented. The design of the test fixture and the finite element analysis performed to determine fixture accuracy are discussed in detail. Additionally, the test procedure is presented, as well as the results for the 32 tests performed.

The task of developing a framework for which agents can communicate reliably and flexibly in open systems is not trivial. This thesis addresses the dichotomy between reliable communication and facilitation of the autonomy of agents to create more flexible and emergent interactions. By the introduction of adaptations to a distributed protocol language, agents benefit from the ability to communicate interaction protocols to elucidate the social norms (thus creating more reliable communication). Yet, this approach also provides the functionality for the agent to unilaterally introduce new paths for the conversation to explore unforeseen opportunities and options (thus restoring more autonomy than possible with static protocols). The foundation of this work is Lightweight Coordination Calculus (LCC). LCC is a distributed protocol language and framework in which agents coordinate their own interactions by their message passing activities. In order to ensure that adaptations to the protocols are done in a reasonable way, we examine the use of two models of communication to guide any transformations to the protocols. We describe the use of FIPA's ACL and ultimately its unsuitability for this approach as well as the more fecund task of implementing dialogue games, an model of argumentation, as dynamic protocols. The existing attempts to develop a model that can encompass the gulf between reliability and autonomy in communication have had varying degrees of success. It is the purpose and the result of the research described in this thesis to develop an alloy of the various models, by the introduction of dynamic and distributed protocols, to develop a framework stronger than its constituents. Though this is successful, the derivations of the protocols can be dificult to reconstruct. To this end, this thesis also describes a method of protocol synthesis inspired by models of human communication that can express the dialogues created by the previous approaches but also have a fully accountable path of construction. Not only does this thesis explore a unique and novel approach to agent communication, it is tested through a practical implementation.

A RESEARCH REPORT SUBMITIED TO THE FACULTY OF ARCHITECTURE. UNIVERSITY OF THE WITWATERSRAND, JOHANNESBURG, FOR THE DEGREE OF MASTER OF SCIENCE IN BUILDING / This research project is an investigation into the effect of the grading of perlite lightweight aggregates on the resultant concrete strengths. Lightweight concretes are reviewed. Perlite, as a lightweight aggregate, is assessed. Grading theory for aggregates and in particular lightweight aggregate is analysed. A series of mix designs are proposed with manipulation of the grading of the perlite as the only variable. This is so that variations in compressive strength and density may be assessed in terms of the grading of the perlite. Those mixes are undertaken and tested for compressive strength and dry density. In this research project compressive strength is considered a benefit, while mass is considered a disadvantage. The performance of a lightweight concrete is assessed firstly in terms of the Power Factor. The Power Factor is the compressive strength divided by the dry density of a concrete. The performance of lightweight concretes produced with Perlite aggregate is assessed secondly in terms of the Cement Content factor. The Cement Content Factor is the Power Factor divided by the Cement Content. This factor has the effect of creating a common denominator of the cement content. An evaluation of the results yields the conclusions detailed in chapter Eight, the principal two being: • The optimal perlite grading tested was a monodisperse, single size fraction, of between 600 and 1180 microns. • The most practical measure for manufacturers to improve the performance of lightweight / Andrew Chakane 2019

There are several ways to virtualize machines from the different closed source variants as VMware ESXi and Windows Hyper-V virtualization to open source varies as Xen and Kernel-based Virtual Machine (KVM). There is also another way to virtualize parts of an operating system to increase versatility and be able to use more of the system’s resources in a more efficient way. LXC (Linux Containers) is a lightweight virtualization that is run on top of the existing operating system by encapsulating applications that is inside the container. LXC works so the kernel of the Linux system is shared by the containers that run next to each other without much knowledge of each other. In that way it can be more resource efficient than virtualizing the entire Linux kernel several times for different applications in a traditional guest to host environment. Many data centers today are already using some variant of virtualization in their production environment, it may then be interesting to examine if there are some other methods that result in better performance for chosen application and power savings when hosts can be turned off. That is why this project has carried out a field study to examine how LXC performs when the host system is virtualized in a hypervisor environment. An organization might want to migrate from a hypervisor environment to a lightweight virtualization environment that is based on containers. The work has been done by doing experiments using two different software to examine I/O to determine if LXC is affected by being nested inside ESXi. The study begins with a small background study to obtain information that will give relevant information from previous done work in relevant fields. The study was conducted with the use of the experimental method to be able to answer the hypothesis and the projects questions. The questions that was answered in the project was: How much degradation of the file system's read and write speeds arises when LXC is nested in ESXi? Does it affect the file system's ability to read and write to disk when there are restrictions on available resources? The result of the experiments show that LXC performs close to equal of the bare metal systems, with a 2 percent loss as a minimum and a maximum of 11 percent in write and read ability to/from disk. When LXC is intertwined with ESXi there is an up to 15 percent loss in write and read ability excluding the loss the hypervisor adds. When restricting the resources for a container down to one processor core and two gigabytes of primary memory experiments show that there was a 3 to 15 percent loss in write and read ability from the disk

"Securing data transmission has always been a challenge. While many cryptographic algorithms are available to solve the problem, many applications have tough area constraints while requiring high-level security. Lightweight cryptography aims at achieving high-level security with the benefit of being low cost. Since the late nineties and with the discovery of side channel attacks the approach towards cryptography has changed quite significantly. An attacker who can get close to a device can extract sensitive data by monitoring side channels such as power consumption, sound, or electromagnetic emanation. This means that embedded implementations of cryptographic schemes require protection against such attacks to achieve the desired level of security. In this work we combine a low-cost embedded cipher, Simon, with a stateof-the-art side channel countermeasure called Threshold Implementation (TI). We show that TI is a great match for lightweight cryptographic ciphers, especially for hardware implementation. Our implementation is the smallest TI of a block-cipher on an FPGA. This implementation utilizes 96 slices of a low-cost Spartan-3 FPGA and 55 slices a modern Kintex-7 FPGA. Moreover, we present a higher order TI which is resistant against second order attacks. This implementation utilizes 163 slices of a Spartan-3 FPGA and 95 slices of a Kintex-7 FPGA. We also present a state of the art leakage analysis and, by applying it to the designs, show that the implementations achieve the expected security. The implementations even feature a significant robustness to higher order attacks, where several million observations are needed to detect leakage."

Bionischer Leichtbau realisiert mit Applikationen an gängige FEM-Programme nach dem Vorbild der Natur

With the remarkable progress in microelectronics and low-power semiconductor technologies, Radio Frequency IDentification technology (RFID) has moved from obscurity into mainstream applications, which essentially provides an indispensable foundation to realize ubiquitous computing and machine perception. However, the catching and exclusive characteristics of RFID systems introduce growing security and privacy concerns. To address these issues are particularly challenging for low-cost RFID systems, where tags are extremely constrained in resources, power and cost. The primary reasons are: (1) the security requirements of low-cost RFID systems are even more rigorous due to large operation range and mass deployment; and (2) the passive tags' modest capabilities and the necessity to keep their prices low present a novel problem that goes beyond the well-studied problems of traditional cryptography. This thesis presents our research results on the design and the analysis of security schemes for low-cost RFID systems. Motivated by the recent attention on exploiting physical layer resources in the design of security schemes, we investigate how to solve the eavesdropping, modification and one particular type of relay attacks toward the tag-to-reader communication in passive RFID systems without requiring lightweight ciphers. To this end, we propose a novel physical layer scheme, called Backscatter modulation- and Uncoordinated frequency hopping-assisted Physical Layer Enhancement (BUPLE). The idea behind it is to use the amplitude of the carrier to transmit messages as normal, while to utilize its periodically varied frequency to hide the transmission from the eavesdropper/relayer and to exploit a random sequence modulated to the carrier's phase to defeat malicious modifications. We further improve its eavesdropping resistance through the coding in the physical layer, since BUPLE ensures that the tag-to-eavesdropper channel is strictly noisier than the tag-to-reader channel. Three practical Wiretap Channel Codes (WCCs) for passive tags are then proposed: two of them are constructed from linear error correcting codes, and the other one is constructed from a resilient vector Boolean function. The security and usability of BUPLE in conjunction with WCCs are further confirmed by our proof-of-concept implementation and testing. Eavesdropping the communication between a legitimate reader and a victim tag to obtain raw data is a basic tool for the adversary. However, given the fundamentality of eavesdropping attacks, there are limited prior work investigating its intension and extension for passive RFID systems. To this end, we firstly identified a brand-new attack, working at physical layer, against backscattered RFID communications, called unidirectional active eavesdropping, which defeats the customary impression that eavesdropping is a ``passive" attack. To launch this attack, the adversary transmits an un-modulated carrier (called blank carrier) at a certain frequency while a valid reader and a tag interacts at another frequency channel. Once the tag modulates the amplitude of reader's signal, it causes fluctuations on the blank carrier as well. By carefully examining the amplitude of the backscattered versions of the blank carrier and the reader's carrier, the adversary could intercept the ongoing reader-tag communication with either significantly lower bit error rate or from a significantly greater distance away. Our concept is demonstrated and empirically analyzed towards a popular low-cost RFID system, i.e., EPC Gen2. Although active eavesdropping in general is not trivial to be prohibited, for a particular type of active eavesdropper, namely a greedy proactive eavesdropper, we propose a simple countermeasure without introducing extra cost to current RFID systems. The needs of cryptographic primitives on constraint devices keep increasing with the growing pervasiveness of these devices. One recent design of the lightweight block cipher is Hummingbird-2. We study its cryptographic strength under a novel technique we developed, called Differential Sequence Attack (DSA), and present the first cryptanalytic result on this cipher. In particular, our full attack can be divided into two phases: preparation phase and key recovery phase. During the key recovery phase, we exploit the fact that the differential sequence for the last round of Hummingbird-2 can be retrieved by querying the full cipher, due to which, the search space of the secret key can be significantly reduced. Thus, by attacking the encryption (decryption resp.) of Hummingbird-2, our algorithm recovers 36-bit (another 28-bit resp.) out of 128-bit key with $2^{68}$ ($2^{60}$ resp.) time complexity if particular differential conditions of the internal states and of the keys at one round can be imposed. Additionally, the rest 64-bit of the key can be exhaustively searched and the overall time complexity is dominated by $2^{68}$. During the preparation phase, by investing $2^{81}$ effort in time, the adversary is able to create the differential conditions required in the key recovery phase with at least 0.5 probability. As an additional effort, we examine the cryptanalytic strength of another lightweight candidate known as A2U2, which is the most lightweight cryptographic primitive proposed so far for low-cost tags. Our chosen-plaintext-attack fully breaks this cipher by recovering its secret key with only querying the encryption twice on the victim tag and solving 32 sparse systems of linear equations (where each system has 56 unknowns and around 28 unknowns can be directly obtained without computation) in the worst case, which takes around 0.16 second on a Thinkpad T410 laptop.