Dendritic or branching structures are commonly seen in natural phenomena such as lightning, cracking and vegetal growth. They are also often used for artistic or decorative purposes, ranging from ornamentation to decorative ceramics. Existing procedural methods for modeling these structures remain very limited in terms of control and flexibility. As a result, these objects tend to be modeled individually, which is a painstaking and costly process.<p>We present a new procedural method for modeling dendritic structures based on a path planning approach. Our method includes the implementation of a partial non-scalar distance metric that gives us effective and flexible control handles over the evolving dendritic structure. These control handles are demonstrated by guiding the growth of dendritic structures using input images, allowing us to create a form of stylistic dendritic halftoning and to embed hidden images in dendritic trees to create pareidolia effects. These applications demonstrate the vast diversity of structures that can easily be modeled by our process a flexibility that existing methods definitely lack. We also demonstrate the application of the partial non-scalar distance metric to the context of texture synthesis from example, and show how it holds promise for many other contexts.

Dendritic or branching structures are commonly seen in natural phenomena such as lightning, cracking and vegetal growth. They are also often used for artistic or decorative purposes, ranging from ornamentation to decorative ceramics. Existing procedural methods for modeling these structures remain very limited in terms of control and flexibility. As a result, these objects tend to be modeled individually, which is a painstaking and costly process.<p>We present a new procedural method for modeling dendritic structures based on a path planning approach. Our method includes the implementation of a partial non-scalar distance metric that gives us effective and flexible control handles over the evolving dendritic structure. These control handles are demonstrated by guiding the growth of dendritic structures using input images, allowing us to create a form of stylistic dendritic halftoning and to embed hidden images in dendritic trees to create pareidolia effects. These applications demonstrate the vast diversity of structures that can easily be modeled by our process a flexibility that existing methods definitely lack. We also demonstrate the application of the partial non-scalar distance metric to the context of texture synthesis from example, and show how it holds promise for many other contexts.

Orientadores: Amauri Garcia, Wislei Riuper Ramos Osorio / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-12T22:54:52Z (GMT). No. of bitstreams: 1 Garcia_LeonardoRicheli_M.pdf: 15499869 bytes, checksum: 1afa8bd79812971da1e6fac7f4fed383 (MD5) Previous issue date: 2008 / Resumo: Sabe-se que existem tendências de leis e diretrizes que restringem o uso e aplicação de certas substâncias perigosas utilizadas em processos de fabricação de componentes em geral. Como exemplo, podem-se citar produtos contendo cádmio, mercúrio, cromo hexavalente, bifenilos polibromatos, éteres difenil-polibromato e chumbo. Devido a essas restrições, fabricantes de produtos eletrônicos têm que adequar seus produtos às novas diretrizes e desenvolver novas ligas de solda sem chumbo. Estudos preliminares indicam que ligas Sn-Zn, particularmente a eutética, consistem em alternativas promissoras para a substituição das ligas de solda contendo chumbo. Entretanto, é necessário avaliar influências das taxas de resfriamento do processo sobre a microestrutura formada e as propriedades mecânicas dessas ligas. O presente trabalho tem exatamente esse objetivo, e para cuja consecução foram planejadas as seguintes atividades: i) solidificação unidirecional de ligas Sn-Zn (Sn-4%Zn, Sn-9%Zn e Sn-12%Zn) e da liga eutética Sn-Pb (para comparação), ii) mergulho de lâminas de cobre em banho das ligas Sn-Zn e Sn- Pb por intermédio de imersão à quente e iii) por deposição em substrato de cobre. Para a fase inicial utilizou-se de um dispositivo de solidificação unidirecional vertical ascendente, para obtenção dos lingotes e registro dos respectivos perfis térmicos experimentais. Foram determinadas as variáveis térmicas de solidificação: coeficiente de transferência de calor metal/molde, velocidades de deslocamento da isoterma liquidus e taxa de resfriamento para as ligas do sistema Sn-Zn e para a liga Sn-Pb (Sn-40%Pb). Estas variáveis foram confrontadas com as previsões teóricas de um modelo numérico de solidificação e, em seguida, correlacionadas com os espaçamentos dendríticos secundários (?2) e equações experimentais de crescimento dendrítico foram determinadas. Foram realizados ensaios de mergulho utilizando-se lâminas (substrato) de cobre, a diferentes temperaturas de mergulho, em que foi possível avaliar a espessura da camada depositada sobre o substrato, a porcentagem da área recoberta pelas ligas e verificar as respectivas microestruturas. Foram também realizados ensaios de molhabilidade para avaliação do ângulo de contato entre cada liga e os respectivos substratos / Abstract: A number of laws and guidelines have been restricted the application of hazardous substances in manufacturing processes of components. This is the case of products containing cadmium, mercury, hexavalent chromium, polibromates biphenyls, polibromate-diphenyl ethers and lead. In order to adequate products to such restriction requirements, electronic components manufacturers have to meet such requirements by developing new lead-free solder alloys. Preliminary studies have indicated that Sn-Zn alloys, in particular the eutectic composition, are promising alternatives to the replacement of solder alloys containing lead. However, studies focusing on the influence of the cooling rate on the resulting microstructures and on the mechanical properties of these alloys need to be carried out. This work has precisely such objective, and the following activities have been planned to attain such purpose: i) unidirectional solidification of Sn-Zn alloys (Sn-4wt%Zn, Sn-9wt%Zn, Sn-12wt%Zn) and of the Sn-Pb eutectic (for comparison purposes), ii) copper blades dipped in molten Sn-Zn and Sn-Pb alloys (hot dipping) and iii) deposition on copper substrate. For the initial experimental step an upward vertical solidification system has been used to obtain the alloys ingots and their correspondent thermal profiles. Solidification thermal variables such as: metal/mold heat transfer coefficient, tip growth rates and cooling rates have been determined for Sn-Zn and the Sn-40wt%Pb alloys. Such experimental variables have been compared with predictions from a solidification numerical model and correlated to secondary dendrite arm spacings (?2) and experimental equations of dendritic growth have been proposed. The thickness of the coating layers, the spreading areas and the resulting microstructures of the alloys on the copper substrates (blades) were evaluated after the hot dipping procedures at different temperatures. Wetting tests have also been carried out in order to evaluate the contact angle between drop and substrate for each alloy / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Orientador: Amauri Garcia / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-09T07:59:55Z (GMT). No. of bitstreams: 1 Rosa_DanielMonteiro_D.pdf: 8184541 bytes, checksum: 0b8d932ad9a1091a507ea6b10e4185f8 (MD5) Previous issue date: 2007 / Resumo: As morfologias das estruturas de solidificação, caracterizadas principalmente por arranjos celulares e dendríticos, e suas grandezas representadas por espaçamentos celulares e dendríticos primários, secundários e terciários, controlam os perfis de segregação e a formação de segundas fases dentro das regiões intercelulares ou interdendríticas, que determinam as propriedades finais das estruturas fundidas. O presente trabalho pretende contribuir para o entendimento do desenvolvimento microestrutural de ligas binárias através da análise de dois sistemas binários que possuem elevada importância para a indústria na fabricação de peças fundidas automotivas e grades de baterias: Al-Si e Pb-Sb, respectivamente. Os experimentos realizados utilizaram dois diferentes dispositivos em que o calor é extraído somente pelo sistema de resfriamento a água, localizado no fundo (solidificação ascendente) e no topo (solidificação descendente) da lingoteira. As variáveis térmicas de solidificação foram determinadas pela leitura de temperaturas a partir de termopares posicionados dentro da lingoteira em diferentes posições em relação à superfície refrigerada. Estas variáveis térmicas foram confrontadas com as previsões teóricas de um modelo numérico de solidificação. Os aspectos macroestruturais e microestruturais foram caracterizados ao longo dos lingotes através de microscopia óptica. Para as ligas Al-Si foi realizada uma análise complementar do efeito da convecção térmica e constitucional nos espaçamentos dendríticos terciários na solidificação unidirecional transitória descendente. Ligas hipoeutéticas Pb-Sb foram utilizadas para analisar as influências das variáveis térmicas de solidificação e da concentração de soluto nas estruturas celulares, na transição celular/dendrítica e nas estruturas dendríticas. Os espaçamentos celulares e dendríticos foram comparados com as previsões teóricas fornecidas pelos principais modelos de crescimento estacionário e transitório da literatura. Foram também examinados os efeitos da taxa de resfriamento no crescimento celular da liga Pb 0,85%Sb e a influência do tamanho celular e do perfil de macrossegregação correspondente na resistência à corrosão / Abstract: The morphologies of as-cast microstructures, characterized mainly by cellular and dendritic patterns, and their scales represented by primary, secondary and tertiary arm spacings, control the segregation profiles and the formation of secondary phases within intercellular and interdendritic regions, which determine the final properties of castings. The present work aims to contribute to the understanding of microstructural development of binary alloys by analyzing two binary systems, which possess high industrial importance in the manufacture of as-cast automotive components and battery grids: Al-Si and Pb-Sb, respectively. Experiments have been carried out by using two castings assemblies, which were designed in such way that heat was extracted only through the water-cooled system, located at the bottom (upward solidification) and at the top (downward solidification) of the casting. The solidification thermal variables have been determined from thermal readings acquired by thermocouples located inside of the casting in different positions from the cooled surface. Such experimental thermal variables have been compared with theoretical predictions of a numerical model of solidification. Macrostructural and microstructural aspects along the casting were characterized by optical microscopy. For Al-Si alloys a complementary analysis of the influence of thermosolutal convection on the tertiary dendrite arm spacing during the downward unsteady-state directional solidification has been carried out. Hypoeutectic Pb-Sb alloys have been used to analyze the influences of solute concentrations and solidification thermal variables in the development of cellular structures, the cellular/dendritic transition and dendritic structures. Experimental cellular and dendritic spacings have been compared with the theoretical predictions furnished by the main steady-state and unsteady-state growth models from the literature. The effect of cooling rate on the cellular growth of a Pb 0.85wt%Sb alloy and the influences of cell size and of the corresponding macrosegregation profile on the resultant corrosion behavior have also been examined. / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

Functional Dendritic Structures from Bile Acids: Supramolelcular Hosts, Light Harvesters and Drug Carriers Chapter 1. An Overview of Functional Dendrimers. Dendrimers are welldefined, hyperbranched macromolecules that are prepared by highly controlled iterative methodologies. The ability to modulate the size, molecular weight, chemical functionalities and the position and number of functional groups in dendrimers make them promising candidates for a wide variety of applications. In this chapter, three areas 1) hostguest chemistry 2) light harvesting and 3) drug delivery, where dendrimers are increasingly finding applications, are discussed with selected examples. Chapter 2. Hydroxyl Terminated Dendritic Oligomers from Bile Acids: Synthesis and Properties. Bile acids are excellent building blocks for dendritic construction because of their many interesting features. They are readily available, chiral, facial amphiphiles with complementary functionalities. Moreover, due to the large size of the bile acid units, a dendritic structure consisting of only a few such repeat units can have an extended structure with multiple functionalizable groups. (figure 1) The high reactivity of the chloroacetyl group has been exploited for the synthesis of bile acid based first and second-generation dendrons with glycolate linkers and multiple hydroxyl groups. The synthesis involves only a few steps and avoids the use of protecting groups for the terminal hydroxyl groups. The synthesis of a bile acid tetramer is shown here as an example (Figure 1). Carboxyl protected cholic acid was reacted with chloroacetylchloride to generate the trischloroacetylated derivative. This compound on reaction with excess of sodium cholate generated the tetramer with nine hydroxyl groups via displacement of the chlorides. In order to synthesize higher generation dendritic structures, perchloroacetylated firstgeneration dendrons were first synthesized. These were subsequently reacted with excess of sodium deoxcholate to generated secondgeneration dendrons with multiple hydroxyl groups (Figure 2). All the compounds were characterized by H NMR, C NMR, IR, ESIMS/MALDI-TOF, HPLC and elemental analysis(wherever possible) Figure 2. Structure of tridecamer. These dendritic structures with facially amphiphilic bile acid backbones on the periphery were able to solubilize cresol red, a hydrophilic dye, in a nonpolar solvent, thus exhibiting reverse micellar characteristics. Chapter 3. Multiple Naproxen Appended Bile Acid Dendrimers as Light Harvesters and Drug Carriers. Part I. Synthesis and Characterization. Using the same synthetic strategy as in Chapter 2, bile acid based dendritic structures appended with multiple bioactive (S)naproxens were generated as potential drug carriers. The construction of these dendrimers was accomplished using per(chloroacetylated) bile acid dendrons and conveniently displacing all the chlorides with naproxen units. Since naproxen is photoactive with a high fluorescence quantum Figure 3. Structures of secondgeneration dendrimers and a monomer with multiple naproxens. yield, the photophysical properties of these multichromophoric dendrimers could be further explored (Figure 3). By functionalizing the carboxyl group on the side chain with an anthracenyl moiety the energy transfer properties of these dendrimers could be studied. In this section the synthesis of first and secondgeneration dendritic structures with multiple naproxen units at the periphery and benzyl/anthracenyl moiety on the side chain are described (Figure 3). Model compounds using monomeric bile acid units were synthesized for comparison with the dendritic structures. All the compounds were characterized by H NMR, C NMR, IR, ESIMS/MALDITOF, HPLC and elemental analysis (wherever possible). Part II: Absorption, Fluorescence and Intramolelcular Energy Tranfer Studies. Absorption studies showed that the molar extinction coefficients increase linearly with increasing number of naproxen units and the absorption spectra of anthracenyl moiety remain unchanged in all the dendritic systems. These indicated the absence of ground state interaction between the chromophores. In the 275-290 nm absorption region, the molar extinction coefficient of naproxen is much greater than that of the 9-anthracenylmethyl chromophore. Hence excitation in this region would mainly excite the naphthalene chromophore. Upon excitation at 275 nm, there was predominant emission from the anthracenyl moiety in the dendritic structures (containing both chromophores) and the fluorescence intensity increased with increasing number of naproxens(Figure4). This indicated that the dendrimers act as efficient light harvesters with energy transfer from naproxen to anthracene (intramolecular nature of the energy transfer was confirmed through control experiments). (Figure 4: Refer PDF File) The fluorescence and energy-transfer properties were further investigated by time-resolved fluorescence spectroscopy. The presence of fast decay component(s) in the naproxen decay in dendritic structures (containing both chromophores) indicates that its fluorescence is quenched in the presence of anthracene due to energy transfer ((λex 275 nm, λem 350 nm (Figure 5). This was further confirmed by monitoring the fluorescence of the sensitized anthracenyl chromophore (λex 275 nm, λem 436 nm) which exhibited a fast rise comparable to he quenched naproxen lifetime(s). The efficiency of energy transfer was estimated by donor quenching by both steadystate and timeresolved techniques. The dendritic structures exhibited high energy transfer efficiencies (~ 70 – 90 %) with the net efficiency decreasing from the first to second-generation. Part III. In vitro Study of Hydrolysis of Naproxen Appended Bile Acid Prodrugs by Chemical and Enzymatic Methods. The naproxen appended bile acid dendrimers consist of hydrolyzable ester and glycolate linkers. Hence the chemical stability and enzymatic degradation with possible release of naproxen was studied. Two compounds, monomer appended with two naproxens and trimer with four naproxens have been used for the initial investigations (Figure 6). The compounds were found to be highly stable towards chemical hydrolysis and did not show any hydrolysis in phosphate buffer, pH = 7.4 even after 7 days. Since the compounds were not soluble in water, Arabic gum and TritonX were used for emulsification. Figure 6. Structures of monomer and trimer. (Refer PDF File) The enzymatic hydrolysis of the compounds was then studied using Candida Rugosa Lipase. In both cases, there was slow hydrolysis of the substrate and intermediates were formed (with release of free naproxen) which were detected by HPLC (reverse phase column with a UV detector). The trimer underwent much slower hydrolysis compared to the monomer. The intermediates were characterized by absorption and mass (ESIMSQTOF) spectrometry.