Im Rahmen der vorgelegten Arbeit wurde das Niederdruck-Hohlteilgießverfahen untersucht. Dieses Verfahren beruht auf dem Niederdruckgießverfahren, jedoch wird die Druckbeaufschlagung auf das System vor dem kompletten Erstarren des Gussstückes beendet, wodurch nicht erstarrtes Material aus der Form fließen kann und ein hohles Gussstück ohne Einsatz von Kernen entsteht. Im Rahmen dieser Arbeit wurden Probekörper aus verschiedenen Al-Legierungen in Sand- und Metallformen hergestellt und ausgewertet, wobei die Einflussfaktoren Druckhaltezeit und Temperaturgradient zwischen Schmelze und Form variiert wurden. Anschließend erfolgte eine Auswertung der Probekörper hinsichtlich Ausbildung der Wanddicke und deren Rauhigkeit. Dabei wurden Abhängigkeiten zwischen Haltezeit und Wanddicke gefunden. Die Rauhigkeit des ausgebildeten Hohlraumes ist dabei legierungsabhängig und unterscheidet sich zwischen Sand- und Kokillenguss stark.

Recycling has proven not only to address today’s economical, environmental and social issues, but also to be imperative for the sustainability of human technology. The current thesis has investigated the feasibility of a new philosophy for Recycling (Alloying-Recycling) using steel 1020 and aluminum 6061T6. The study was limited to the metallurgical aspects only and has highlighted the potential of recycled alloys made of recycled aluminum and steel to exhibit substantially increased wear resistance and strength-to-weight ratio as compared to initial primary materials. Three alloy-mixtures are considered: TN3 (5wt% 1020 +95wt% 6061T6); TN5 (0.7wt% 1020 + 99.3wt% 6061T6); and TN4 (10wt% 6061T6 + 90wt% 1020). A Tucker induction power supply system (3kW; 135-400 kHz) is used to melt the alloy mixtures for casting in graphite crucibles. Heat treatment of the cast samples is done using a radiation box furnace. Microscopy, Vickers hardness and pin-on-disc abrasive wear tests are performed. Casting destroyed the initial microstructures of the alloys leading to a hardness reduction in the as-cast and solution heat-treated aluminum rich samples to 60 Hv from 140 Hv. Ageing slightly increased the hardness of the cast samples and provided a wear resistance two times higher than that of the initial 6061T6 material. On the steel rich side, the hardness of the as-cast TN4 was 480 Hv, which is more than twice as high as the initial hardness of steel 1020 of 202 Hv; this hints to strong internal and residual stress, probably martensite formation during fast cooling following casting. Solution heat treatment lowered the hardness to the original value of steel 1020, but provided about ten (10) times higher wear resistance; this suggests higher ductility and toughness of normalised TN4 as compared to 1020. In addition, TN4 exhibits about 25% weight reduction as compared to 1020. The actual recycling process and the effect of non-metallic impurities shall be investigated in future works. Also, the casting and heat treatment processes need to be improved.

The use of light-weight building materials in modern construction has resulted in efficient designs and considerable cost savings by reducing structural weight and supporting sections. This has only been possible because of many years of research to better understand the properties of the light-weight material, and its structural behaviors. However, light-weight grout is a relatively new building material in reinforced masonry construction and little is known about its structural properties. The main objective of this study was to determine if the use of light-weight grout would impact the performance of reinforcing steel, specifically development length, in masonry construction.The research included testing masonry wallettes made with normal and light-weight grout containing No. 4 (12 mm) bars with splice lengths as prescribed by the current design equation as well as splices with a modification factor. The modification factor was based on preliminary grout testing, using the procedure given in the concrete building code. The wallettes were tested in a tension test to determine if the splices were of sufficient length to fully develop the yield stress of the reinforcement.For small bar sizes, No. 4 or smaller, it is not necessary to include a modification factor when calculating development length. The minimum length of lap of 12 in. governs when No. 4 or smaller bars are used, and provides sufficient length to fully develop the yield stress of the reinforcement both for normal and light-weight grout types.

Published Article / The purpose of this paper is to analyse the thermal performance of two buildings. The one has a large thermal mass and the other a highly insulated low thermal mass. A typical 120 m2 suburban building was modelled in Ecotect. As part of the model infiltration rate, wind sensitivity and a central Pretoria weather file were used. New material composites were introduced in the materials database to represent typical building materials used in the construction of heavy and light-weight buildings in South Africa. The thermal characteristics of these new materials were then calculated within Ecotect. Ecomat was used to calculate thermal lag which was used as an additional input into Ecotect. The research indicates that a low thermal mass and highly insulated building have been shown to use 18.3% less annual space heating and cooling energy when compared to the high thermal mass building. The good thermal performance results of the light-weight building will help in clearing scepticism to adopting this construction technology in southern Africa where high thermal mass masonry is still predominant.

A tecnologia construtiva em chapas delgadas estruturadas em Light Steel Framing (LSF) vem sendo introduzida no mercado nacional como uma alternativa para substituir a tecnologia tradicional com vedações externas em alvenaria e revestimentos aderidos, comumente utilizada para execução de fachadas em edifícios de múltiplos pavimentos. Trata-se de uma tecnologia com montagem a seco que traz potenciais benefícios em relação ao método tradicional de produção de fachadas, notadamente em relação a: otimização da logística no canteiro de obra; simplificação dos procedimentos de acompanhamento e controle das etapas executivas; alta produtividade, com potencial redução dos prazos de obra; fácil controle sobre o custo final do serviço; e redução de riscos quanto ao cumprimento dos prazos planejados para o desenvolvimento e conclusão da atividade. O objetivo do presente trabalho é comparar os diferenciais no planejamento da obra e no custo de produção entre essa tecnologia e o método tradicional para execução de fachadas de edifícios de múltiplos pavimentos, considerando-se um mesmo projeto arquitetônico. Como método para o desenvolvimento do trabalho, adotou-se: pesquisa bibliográfica; entrevistas com profissionais, fabricantes e empresas especializadas na montagem da tecnologia em chapas delgadas estruturadas em Light Steel Framing (LSF); pesquisa quanto às alternativas disponíveis para o LSF e quanto aos custos praticados no mercado nacional para ambas as tecnologias; e acompanhamento de obras em LSF visando aprofundar os conhecimentos sobre seu método de execução de fachada. Pela escassa literatura nacional sobre o tema e pelo ainda incipiente conhecimento sobre esta tecnologia no meio técnico e acadêmico, acredita-se que o presente trabalho apresenta informações relevantes para profissionais ou empresas dispostas a inovar na execução desse importante subsistema das edificações, adotando a tecnologia com painéis leves em seus futuros projetos. / The building technology of light weight external sheets structured in Light Steel Framing (LSF) has been introduced in the domestic market as an alternative to replace traditional exterior masonry and mortar cladding technology commonly used for façade construction in multiple floors buildings. It is a technology with dry assembly that brings potential benefits in relation to the traditional method of façade production, especially in relation to: optimization of the logistics in the construction site; simplification of procedures for monitoring and controlling the executive stages; high productivity, with potential reduction of work deadlines; easier control over the final cost of the service; and reduction of risks regarding compliance with the deadlines planned for the development and completion of the activity. The objective of the present work is to compare the differentials in the planning of the work and the cost of production between this technology and the traditional method for the execution of façades of multiple floors buildings, considering the same architectural design. As a method for the development of the work, it was adopted: bibliographic research; interviews with professionals, manufacturers and companies specializing in the assembly of thin sheet structured in Light Steel Framing (LSF) technology; research on the alternatives available to the light weight external sheets structured in LSF technology and on the costs practiced in the national market for both technologies; follow-up of works in LSF aiming to deepen the knowledge about its method of execution of facade. Due to the scarce national literature on the subject and the still incipient knowledge about this technology in the technical and academic environment, it is believed that the present work presents relevant information for professionals or companies willing to innovate in the execution of this important subsystem of the buildings, adopting the technology with light weight panels for façade production in their future projects.

In this thesis we propose a complete solution of authentication and key exchange for digital home environments such that mobile devices can securely access the home devices. Some digital home authentication and key exchange protocols performed between mobile devices and home gateways are assisted by the AAA servers, which are provided by telecommunication companies, but they have some security flaws. In our proposed protocol, the necessary security requirements for digital home secu-rity mechanisms are satisfied, such as mutual authentication, authenticated key ex-change, and forward secrecy. In our digital home security scheme, a mobile device can authenticate his home gateway and exchange a session key with each home de-vice without pre-sharing keys with the home gateway and with the home device. The proposed authentication and key exchange protocol can also cooperate with the AAA server. Furthermore, we propose another authentication and key exchange protocol with forward secrecy between mobile devices and home devices. The computation capabilities of the mobile devices also are considered in our proposed protocols, where we only employ symmetric encryption/decryption and low-cost op-erations in order to reach the aim of light-weight computation cost.

Constructing multi floor buildings by light weight material have increased recently. There are many advantages of using light weight material, such as wood, for the environment. However, one of the deficiencies of lightweight material is the acoustic performance. Transmission of sound and vibration through floors in multi floor buildings in wood is a drawback to be considered. There are many studies that have addressed this issue. It is most common to make a finite element models well as experiments in laboratory. In these studies the material properties in the FE model are probably often adjusted to correlate to the laboratory experiments, since there is a large spread in material properties found in literature. This thesis however tries to elaborate on the actual material properties of the included wooden elements. Dynamic testing is done to determine the spread (here spread means gap between material properties) in material properties of wooden elements. The materials tested are chipboards and two types of wooden beams. The examined beams are both normal wooden beams and laminated veneer lumber beams. When the dynamic behaviour is known for the wooden parts, they are assembled to two small floor systems. The floor systems consist of four beams and one wooden board. The assembly is dynamically tested in laboratory and in FE software. The FE model used the known material properties for each individual building part. The results from the FE model correlate well with the laboratory tests. This shows that when material properties are known a FE model can predict the real behaviour. However, the examined material properties show a large spread from beam to beam, etc and a better knowledge about the material properties of used wooden parts is needed. / Att bygga flervåningshus med lätta byggmaterial har blivit allt vanligare. Det finns många fördelar med att använda lätta material, såsom trä. En av fördelarna är att det är skonsamt för miljön. Emellertid är en av bristerna i lättviktsmaterial den akustiska prestandan. Överföring av ljud och vibrationer genom golv i flervåningshus i trä är en nackdel att överväga. Det finns flera studier som har behandlat denna fråga. Ofta görs finita element modeller samt tester i laboratorium. I dessa studier justerar man materialegenskaperna i FE-modellen för att korrelera mot laboratorieexperiment. Detta eftersom det finns en stor spridning i materialegenskaperna för trä i litteraturen. Med detta examensarbete, undersöks de faktiska materialegenskaperna hos träelementen genom försök. Dynamiska tester utförs för att bestämma spridningen i materialegenskaper. De testade materialen är spånskivor och två typer av träbalkar. De undersökta balkarna är både normala träreglar och laminerade faner balkar. När det dynamiska beteendet är känt för trädelarna, monteras de ihop till två små golvsystem. Golvsystemen består av fyra balkar och en träskiva. Den assemblerade modellen testas både dynamiskt i ett praktiskt försök och i ett FE program. I FEmodellen används de tidigare framtagna faktiska materialegenskaper för varje ingående enskild byggnadsdel. Resultaten från FE-modellen korrelerar väl med de praktiska experimenten. Med detta examensarbete visas att när materialegenskaperna är kända kan FE-modellen förutsäga det verkliga beteendet. De undersökta materialegenskaperna visar dock en stor spridning från balk till balk, etc. och mer kunskap om materialegenskaper hos trädelar behövs.

The first line of defence against wireless attacks in Radio Frequency Identi cation (RFID) systems is authentication of tags and readers. RFID tags are very constrained in terms of power, memory and size of circuit. Therefore, RFID tags are not capable of performing sophisticated cryptographic operations. In this dissertation, we have designed light-weight authentication schemes to securely identify the RFID tags to readers and vice versa. The authentication schemes require simple binary operations and can be readily implemented in resource-constrained Radio Frequency Identi cation (RFID) tags. We provide a formal proof of security based on the di culty of solving the Syndrome Decoding (SD) problem. Authentication veri es the unique identity of an RFID tag making it possible to track a tag across multiple readers. We further protect the identity of RFID tags by a light-weight privacy protecting identifi cation scheme based on the di culty of the Learning Parity with Noise (LPN) complexity assumption. To protect RFID tags authentication against the relay attacks, we have designed a resistance scheme in the analog realm that does not have the practicality issues of existing solutions. Our scheme is based on the chaos-suppression theory and it is robust to inconsistencies, such as noise and parameters mismatch. Furthermore, our solutions are based on asymmetric-key algorithms that better facilitate the distribution of cryptographic keys in large systems. We have provided a secure broadcast encryption protocol to effi ciently distribute cryptographic keys throughout the system with minimal communication overheads. The security of the proposed protocol is formally proven in the adaptive adversary model, which simulates the attacker in the real world.

The first line of defence against wireless attacks in Radio Frequency Identi cation (RFID) systems is authentication of tags and readers. RFID tags are very constrained in terms of power, memory and size of circuit. Therefore, RFID tags are not capable of performing sophisticated cryptographic operations. In this dissertation, we have designed light-weight authentication schemes to securely identify the RFID tags to readers and vice versa. The authentication schemes require simple binary operations and can be readily implemented in resource-constrained Radio Frequency Identi cation (RFID) tags. We provide a formal proof of security based on the di culty of solving the Syndrome Decoding (SD) problem. Authentication veri es the unique identity of an RFID tag making it possible to track a tag across multiple readers. We further protect the identity of RFID tags by a light-weight privacy protecting identifi cation scheme based on the di culty of the Learning Parity with Noise (LPN) complexity assumption. To protect RFID tags authentication against the relay attacks, we have designed a resistance scheme in the analog realm that does not have the practicality issues of existing solutions. Our scheme is based on the chaos-suppression theory and it is robust to inconsistencies, such as noise and parameters mismatch. Furthermore, our solutions are based on asymmetric-key algorithms that better facilitate the distribution of cryptographic keys in large systems. We have provided a secure broadcast encryption protocol to effi ciently distribute cryptographic keys throughout the system with minimal communication overheads. The security of the proposed protocol is formally proven in the adaptive adversary model, which simulates the attacker in the real world.

Möjligheter att reducera vikten på en hydraulmotor, som tillverkas på Parker Hannifin AB i Trollhättan, har studerats. Målet med arbetet var att ge förslag på hur motorn kan göras lättare för att nå det framtida målet att erbjuda kunder en lättviktsmotor (LWM) lämpad som fläktmotor. För att identifiera komponenterna och deras vikter vägdes alla delar var för sig. Värdena visade att trumhus, lagerhus, axel och lagerpaket stod för ca 75 % av motorns totala vikt. Arbetet koncentrerades därför på att reducera vikten på dessa delar. Flera koncept togs fram med lägre vikt och bibehållen prestanda. Vissa delar kontrollerades mot hållfasthet med handberäkningar och FEM-analyser. Enligt beräkningarna finns möjlighet att reducera vikten med 45 %. Om hydraulmotorn konstrueras enligt koncepten, bör det framtida målet kunna nås, till-verkning av en lättviktsmotor som är betydligt lättare än dagens hydraulmotor. / The weight reducing possibilities for a hydraulic motor, produced by Parker Hannifin AB in Trollhättan, have been investigated. The goal was to provide suggestions for weight optimization to offer customers a light weight motor (LWM) that is well suited as a fan motor. The mass of each part was determined and their functions were identified. The result showed that the housings, shaft and bearings represented 75% of the motor’s total mass. The work was thus concentrated to these parts. Multiple suggestions were generated where weight and performance were taken into consideration. Some parts were analyzed with the aid of FEA-software and hand calculations. The result indicates that a weight reduction of 45% is possible. If the hydraulic motor is redesigned according to the concepts, the goal of a light weight motor can be achieved.