Timing-Constrained Global Routing with Buffered Steiner Trees

This dissertation deals with the combination of two key problems that arise in the physical design of computer chips: global routing and buffering. The task of buffering is the insertion of buffers and inverters into the chip's netlist to speed-up signal delays and to improve electrical properties of the chip. Insertion of buffers and inverters goes alongside with construction of Steiner trees that connect logical sources with possibly many logical sinks and have buffers and inverters as parts of these connections. Classical global routing focuses on packing Steiner trees within the limited routing space. Buffering and global routing have been solved separately in the past. In this thesis we overcome the limitations of the classical approaches by considering the buffering problem as a global, multi-objective problem. We study its theoretical aspects and propose algorithms which we implement in the tool BonnRouteBuffer for timing-constrained global routing with buffered Steiner trees. At its core, we propose a new theoretically founded framework to model timing constraints inherently within global routing. As most important sub-task we have to compute a buffered Steiner tree for a single net minimizing the sum of prices for delays, routing congestion, placement congestion, power consumption, and net length. For this sub-task we present a fully polynomial time approximation scheme to compute an almost-cheapest Steiner tree with a given routing topology and prove that an exact algorithm cannot exist unless P=NP. For topology computation we present a bicriteria approximation algorithm that bounds both the geometric length and the worst slack of the topology. To improve the practical results we present many heuristic modifications, speed-up- and post-optimization techniques for buffered Steiner trees. We conduct experiments on challenging real-world test cases provided by our cooperation partner IBM to demonstrate the quality of our tool. Our new algorithm could produce better solutions with respect to both timing and routability. After post-processing with gate sizing and Vt-assignment, we can even reduce the power consumption on most instances. Overall, our results show that our tool BonnRouteBuffer for timing-constrained global routing is superior to industrial state-of-the-art tools

Potentials and Barriers for Tantalum Recovery from Waste Electric and Electronic Equipment

Circular economy approaches aim to close material cycles along the value chain. As such, the circular economy can be a long-term strategy to mitigate the risks of critical raw material (CRM) supply. Tantalum, with a current end-of-life recycling rate of less than 1%, has been intermittently discussed as critical. Even though the specificity of tantalum applications and high-mass fractions of tantalum in relevant components provide good boundary conditions, recycling barriers hinder the successful implementation of recycling technologies. With this case study, we identify potentials and barriers for implementing the recovery of CRM, using the example of tantalum. To this end, information about visually identifiable tantalum capacitors (VICs) and printed circuit boards (PCBs) in various equipment types was obtained by disassembly campaigns for mobile phones, smartphones, tablets, notebooks, desktop personal computers, flat screen monitors, servers, etc., and the chemical analyses of resulting fractions. Results show great differences in the application of tantalum in various equipment types. Because of this, the tantalum potential of put-on-market (POM) or of waste electric and electronic equipment (WEEE) devices differs between products and regions. Worldwide, the highest POM tantalum flows originate from desktop computers, but in Germany they originate from notebooks. A focus on particular products leads to higher yields in recycling and supports circular economy approaches. Recycling of tantalum from WEEE is generally possible. But an accurate separation of tantalum from PCBs is not feasible solely by separation of VICs. This process also leads to the loss of silver. Further, this study reveals potential miniaturization trends, decreasing the use of VICs, with an anticipated substitution of tantalum with niobium. These barriers impede long-term recycling strategies for tantalum aimed at establishing a circular economy

Simulação numérica para otimização de um motor de baixa cilindrada para competição de eficiência energética

TCC (graduação) - Universidade Federal de Santa Catarina. Campus Joinville. Engenharia Automotiva.O aquecimento global é um dos maiores problemas que a sociedade moderna está enfrentando, e a fonte de energia mais utilizada nos veículos de hoje, os combustíveis nos motores de combustão interna, são um dos maiores vilões. Este assunto tem sido amplamente discutido por agências governamentais, instituições de pesquisa e pela indústria, pressionando-as a encontrar soluções, desenvolvendo motores mais limpos e mais eficientes. Visando essas soluções, a Shell Oil Company criou a competição Shell Eco Marathon (SEM) para incentivar os estudantes universitários a projetar e construir alguns dos protótipos veiculares mais eficientes do mundo, com base nas matrizes energéticas existentes. Neste trabalho, ao combinar a análise computacional, usando AVL-BOOST, com uma ferramenta de melhoria contínua (Design of Experiments - DOE), foi realizado um estudo de otimização de motores. Para este fim, foi utilizado um motor de combustão interna de um cilindro, de 35,8cc e 1,4hp, de ignição por faísca, usado pela equipe EFICEM/CTJ/UFSC na Shell Eco-Marathon. A simulação numérica requer a alimentação do programa com os parâmetros geométricos e de operação do motor e, usando DOE para alternar alguns desses parâmetros, tais como razão de compressão, geometria e tamanho da tubulação, tempo de válvula e avanço da ignição, tornou possível determinar o melhor desempenho possível do motor comparando o resultado com os dados obtidos da documentação técnica do motor, bem como as curvas de operação de potência e torque para a validação e otimização do modelo. Os modelos de transferência de calor utilizados em tubulações e cilindros, assim como o modelo de combustão, foram escolhidos com base na revisão da literatura. Dependendo do parâmetro explorado do motor, foi possível obter melhorias na faixa de 11% a 26% no consumo específico de combustível, potência e torque.Global warming is one of the major problems that modern society is facing, and the most widely used energy source in vehicles today, the fuels in the internal combustion engines, are one of the biggest villains. This matter has been discussed widely by government agencies, research institutions, and the industry, pressing them to find solutions, developing cleaner and more efficient engines. Aiming at these solutions, Shell Oil Company created the Shell Eco Marathon (SEM) competition to encourage university students to design and build some of the world’s most efficient vehicular prototypes based on the existing energy matrices. In this work, while combining computational analysis, using AVL-BOOST, with a continuous improvement tool (Design of Experiments - DOE), an engine optimization study was performed. For this purpose, a single-cylinder, 35,8cc, 1,4hp, spark-ignition internal combustion engine, used by the EFICEM/CTJ/UFSC at the Shell Eco-Marathon, was used. The numerical simulation requires to feed the software with the engine’s geometric and operation parameters and, using DOE to alternate some of these parameters such as compression ratio, pipeline geometry and size, valve timing, and spark advance made it possible to determine the best possible engine performance comparing the result with data obtained from the engine’s technical documentation as well as the power and torque operation curves for the model validation and optimization. The heat transfer models used in pipelines and cylinders, as well as the combustion model, were chosen based on the literature review. Depending on the explored engine parameter, it was possible to obtain improvements in the range of 11% to 26% in the specific fuel consumption, power and torque

Potential and recycling strategies for LCD panels from WEEE

Indium is one of the strategically important materials, which have been characterized as critical by various industrialized countries. Despite its high relevance, only low recycling rates are realized. Its main application is in indium tin oxide (ITO), which is used in the production of liquid crystal displays (LCD). However, recovery strategies for indium from LCDs are not yet being implemented in recycling practices. Although LCDs consist of a sandwich compound with additional materials such as glass (80% ± 5%) and polarizer foils (20% ± 5%), recently published recycling approaches focus mainly on the recovery of indium exclusively. This study, first of all, provides information about the quantity and quality of the materials applied in the LCD panels of the various equipment types investigated, such as notebooks, tablets, mobile phones, smartphones, PC monitors, and LCD TVs. The highest indium mass fraction per mass of LCD was determined in mobile phones and the least indium was found in smartphones. Additionally, we found the significant use of contaminating metals like antimony, arsenic, lead, and strontium in the glass fraction. Thus, specific recovery strategies should focus on selected equipment types with the highest indium potential, which is directly related to the sales of new devices and the number of collected end-of-life devices. Secondly, we have developed and successfully tested a novel recycling approach for separating the sandwich compound to provide single output fractions of panel glass, polarizer foils, and an indium concentrate for subsequent recycling. Unfortunately, the strongly varying content of contaminating metals jeopardizes the recycling of this output fraction. Nonetheless, economic recycling approaches need to address all materials contained, in particular those with the highest share in LCD panels such as polarizer foils and panel glass

Synthesis and Characterization of Novel Isosorbide‐Based Polyester Derivatives Decorated with α ‐Acyloxy Amides

The synergy of multicomponent reactions (MCRs) and metathesis chemistry is applied for the synthesis of bio-based functional isosorbide polymers (i.e., polyesters) decorated with α-acyloxy amide motif. The chemical structure of the polyesters that are not accessible by any other conventional methodologies is characterized in-depth via nuclear magnetic resonance, size-exclusion chromatography, and attenuated total reflectance infrared spectroscopy. It is also observed that the “biomass-derived” carbon % of the polymers varied between 66.2 and 76.9. Moreover, the thermal properties of the novel isosorbide-based polymers are investigated via thermogravimetric analysis and differential scanning calorimetry, revealing that the polymers are in the amorphous state, identified by the glass transition temperature (T$_g$) values below the human body temperature. The mechanical properties and the biocompatibility of the functional novel polyester derivative with the highest “biomass-derived” carbon % are evaluated via dynamic mechanical analysis and cytotoxicity test. The exemplary polymer is biocompatible with chondrocyte cells in the conditions used in the tests. In summary, the complementary nature of isosorbide derivatives with MCRs and metathesis chemistry is utilized to illustrate the potential utility of isosorbide as a building block for polymers with prospective biomedical application (namely, as novel cartilage materials)

Feedback cooling of a single trapped ion

Based on a real-time measurement of the motion of a single ion in a Paul trap, we demonstrate its electro-mechanical cooling below the Doppler limit by homodyne feedback control (cold damping). The feedback cooling results are well described by a model based on a quantum mechanical Master Equation.Comment: 4 pages, 3 figure

Carboxy-Terminal Conversion of Profibrillin to Fibrillin at a Basic Site by PACE/Furin-Like Activity Required for Incorporation in the Matrix

Fibrillin-1, the main component of 10-12 nm microfibrils of the extracellular matrix, is synthesized as profibrillin and proteolytically processed to fibrillin. The putative cleavage site has been mapped to the carboxy-terminal domain of profibrillin-1, between amino acids arginine 2731 and serine 2732, by a spontaneous mutation in this recognition site that prevents profibrillin conversion. This site contains a basic amino acid recognition sequence (R-G-R-K-R-R) for proprotein convertases of the furin/PACE family. In this study, we use a mini-profibrillin protein to confirm the cleavage in the carboxy-terminal domain by both fibroblasts and recombinantly expressed furin/PACE, PACE4, PC1/3 and PC2. Site-directed mutagenesis of amino acids in the consensus recognition motif prevented conversion, thereby identifying the scissile bond and characterizing the basic amino acids required for cleavage. Using a PACE/furin inhibitor, we show that wild-type profibrillin is not incorporated into the extracellular matrix until it is converted to fibrillin. Therefore, profibrillin-1 is the first extracellular matrix protein to be shown to be a substrate for subtilisin-like proteases, and the conversion of profibrillin to fibrillin controls microfibrillogenesis through exclusion of uncleaved profibrillin