Embedded memories dominate area, power and cost of modern very large scale integrated circuits system on chips ( VLSI SoCs). Furthermore, due to process variations, it becomes challenging to design reliable energy efficient systems. Therefore, fault-tolerant designs will be area efficient, cost effective and have low power consumption. The idea of this project is to design embedded memories where reliability is intentionally compromised to increase storage density. Gain cell memories are smaller than SRAM and unlike DRAM they are logic compatible. In multilevel DRAM storage density is increased by storing two bits per cell without reducing feature size. This thesis targets multilevel read and write schemes that provide short access time, small area overhead and are highly reliable. First, timing analysis of reference design is performed for read and write operation. An analytical model of write bit line (WBL) is developed to have an estimate of write delay. Replica technique is designed to generate the delay and track variations of storage array. Design of replica technique is accomplished by designing replica column, read and write control circuits. A memory controller is designed to control the read and write operation in multilevel DRAM. A multilevel DRAM is with storage capacity of eight kilobits is designed in UMC 90 nm technology. Simulations are performed for testing and results are reported for energy and access time. Monte Carlo analysis is done for variation tolerance of replica technique. Finally, multilevel DRAM with replica technique is compared with reference design to check the improvement in access times.

Cílem disertační práce bylo připravit trojrozměrné biokeramické podpůrné systémy („skafoldy“), které by v budoucnu mohly pomoci při rekonstrukci a regeneraci poškozených kostních tkání. Porézní keramické pěny byly připraveny dvěma způsoby – replikační technikou a polymerizací in situ. Co se složení týče, byly studovány keramické materiály zejména na bázi oxidu hlinitého, zirkoničitého a kalcium fosfátů. Byl studován jednak vliv procesních parametrů jako je složení suspenzí a jejich viskozit, dále pak vliv tepelného zpracování na strukturu a výsledné vlastnosti připravených materiálů. U slinutých pěn byla pomocí rastrovací elektronové mikroskopie hodnocena zejména morfologie – velikost pórů, jejich propojenost a celková porozita, charakterizace mikrostruktury nebyla opomenuta. Dále bylo stanoveno fázové složení a pevnost v tlaku. Z biologických vlastností byla testována a diskutována bioaktivita a cytotoxicita materiálů. Disertační práce je členěna do několika částí. V literární rešerši je popsána stavba a vlastnosti kosti, požadavky kladené na kostní náhrady, výhody a nevýhody současně používaných materiálů a způsoby přípravy keramických pěn. Následuje experimentální část, kde byly nejprve studovány pěny připravené replikační technikou. Všechny takto vyrobené pěny měly propojené póry o velikostech 300 až 2000 m, celková porozita se pohybovala v rozmezí 50 – 99 %. Pevnost pěn na bázi kalcium fosfátů – 0,3 MPa (při celkové porozitě 80%) byla nedostatečná pro kostní náhrady, kde je požadována pevnost větší než 2 MPa. Kalcium fosfátové keramiky byly tedy zpevněny buďto inertním jádrem na bázi oxidu hlinitého nebo ATZ (oxidem zirkoničitým zhouževnatělým oxidem hlinitým). Dále byl přípraven částicový kompozit, ve kterým byl hydroxyapatit pojený oxidem křemičitým. Pevnost pěn se podařilo zvýšit až na více než 20 MPa. V poslední kapitole experimentální části byly studovány keramické pěny pěněné in situ, kde byly póry vytvářeny oxidem uhličitým unikajícím během reakce mezi diisokyanátem a polyalkoholem. Po vypálení polymerního pojiva měly pěny propojené póry o průměrné velikosti 80 až 550 m. Celková porozita se pohybovala v rozmezí 76 – 99%. Výhodou oproti replikační technice byly plné trámečky bez velké středové dutiny vznikající vypálením polymerní předlohy. Žádný ze studovaných materiálů nebyl pro buňky toxický, navíc všechny studované pěny vykazovaly bioaktivní chování. Z hlediska kostního tkáňového inženýrství se jako nejslibnější jeví kompozitní materiál zpevněný oxidem křemičitým.

A ceramic systems ability to provide a restoration well adapted and fulfilling the patients clinical and esthetic requirements is its most important technical feature. A CAD / CAM machine unit must be able of designing and milling different restorative materials, such as: resin-matrix ceramics, polycrystalline ceramics and glass-matrix ceramics. The purpose of this study was to present two articles that evaluated weather or not the milling strategy of different all-ceramic crown materials has an influence on the final cementation space. Specifically, the two articles evaluated: article I - The cementation space assessed by the most commonly used method- silicone replica technique- correlating stereomicroscope analysis with micromotomography (-CT); article II: The two-dimensional measures of cementation space were correlated with volume values by using -CT analysis, to better understand the behavior of 2D values in a tridimensional view. In both articles, single crowns were milled in lithium-disilicate, resin nanoceramic and zirconia. In article I, one hundred twenty measurements of each material were used to correlate the methodologies: stereomiscrocope and -CT. The Pearson correlation coefficient test showed a correlation between the methods (p= 0.000, r=+0.455). A similarity in the pattern of statistically significant differences among the regions evaluated (axial, occlusal, marginal) for both methodologies seems to exist. The positive correlation between the methods of measurements of cement space suggests that the internal dimensions of the materials varied because the different strategies after milled of them. In article II, twenty-eight slices were evaluated in three regions: marginal, axial and occlusal, totaling eighty-four measurements for each specimen. Axial and Marginal region showed positive correlation (p=0.000, r=+0.656; p=0.000, r=+0.677, respectively), while occlusal space presented negative correlation (p=0.003, r=0.526). The correlation between 2D and volumetric analysis allow to achieving as more information as possible to improve CAD/CAM systems. / As principais características dos sistemas cerâmicos é a capacidade de abranger estética e boa adaptação clínica. A tecnologia CAD/CAM é capaz de projetar e fresar diferentes materiais, como: cerâmicas de matriz resinosa, policristalinas, e ainda, cerâmicas de matriz vítrea. O objetivo deste trabalho é apresentar dois artigos que avaliam se a estratégia de fresagem de diferentes materiais cerâmicos influenciam no espaço final de cimentação. No primeiro artigo, especificamente, o espaço de cimentação foi avaliado pela metodologia mais utilizada, réplica de silicona. A película de silicona foi mensurada através da estereomicroscopia e microtomografia computadorizada (-CT) e as metodologias foram correlacionadas. No segundo artigo, através da metodologia de -CT, as medidas bidimensionais do espaço de cimentação foram correlacionadas com o volume obtido, a fim de compreender melhor o comportamento dos valores 2D numa visão tridimensional. Em ambos artigos, coroas unitárias foram fresadas em dissilicato de lítio, resina nanocerâmica e zircônia. No artigo I, cento e vinte medidas foram utilizadas para correlacionar as metodologias empregadas, estereomicroscopia e -CT. O teste de correlação de Pearson apresentou correlação entre os métodos (p= 0.000, r=+0.455). Uma similaridade no padrão de diferenças estatisticamente significantes nas regiões avaliadas (axial, oclusal, marginal) parece existir entre as metodologias. A correlação positiva entre os métodos de mensuração do espaço de cimentação sugerem que as dimensões internas variam por conta dos diferentes processos que as coroas são submetidas após a fresagem. No artigo II, oitenta e oito fatias obtidas pelo -CT foram avaliadas em três regiões: marginal, axial e oclusal, totalizando oitenta e quatro medidas por espécime. A correlação positiva entre os métodos de mensuração do espaço de cimentação sugerem que as dimensões internas variam por conta dos diferentes processos que as coroas são submetidas após a fresagem. Artigo II, oitenta e oito fatias foram avaliadas em três regiões: marginal, axial e oclusal, totalizando oitenta e quatro medidas por espécime. Houve correlação positiva entre as regiões axial e marginal (p=0.000, r=+0.656; p=0.000, r=+0.677, respectivamente) e negativa na oclusal (p=0.003, r= -0.526). A correlação entre as avaliações bi e tridimensionais permitem obter mais informações possíveis para aprimorar o sistema CAD/CAM.

Grease-lubricated journal bearings present a common challenge for construction equipment manufacturers in the world. The common design methodology is based on empirical data and has worked very well historically because the market and governments have accepted that bearings in construction equipment need frequent lubrication and exchange of worn parts. Legal and market requirements will soon demand lower environmental impact and increased machine efficiency. These requirements call for better methods of designing grease lubricated journal bearings. The goal of the outlined work was to develop better design methods for grease lubricated journal-bearing design used in heavy-duty construction equipment machines, in order to prolong life and lubrication intervals. The research approach of the project can roughly be divided into three phases: 1. Development of test apparatus and test methods for journal bearing studies. 2. Bench tests of grease lubricated journal bearing design. 3. Verification between bench tests and computer simulations. In the thesis the current state of the art in bearing design for construction equipment is discussed and summarized in the form of design guidelines. The suggested design steps are just a mean to get to the starting point of design. The simple guidelines do however serve a purpose when collected since most published bearing design guidelines are aimed at the bushing material or at continuously rotating bearings. The influence of housing, environment and load cases can not be ignored when designing a bearing. Long term field-testing and experience can not be replaced until better design criteria have been established. Paper A deals with the design of the bearing test apparatus that was built and evaluated. Comparisons between theoretical contact and contact elements in Finite Element program have been made and discussed in paper B. In paper C a replica technique for measuring wear of large field specimens was evaluated. A case study of bearing housing design was performed in paper D utilizing Finite Element program and then validated in paper E in the bearing test apparatus. The influence of grease groove design on bushing life was tested and evaluated in paper F. Wear simulation of a plain bushing has been performed with a Finite Element program and presented in paper G. / QC 20100930