Growth laws and self-similar growth regimes of coarsening two-dimensional foams: Transition from dry to wet limits

We study the topology and geometry of two dimensional coarsening foams with arbitrary liquid fraction. To interpolate between the dry limit described by von Neumann's law, and the wet limit described by Marqusee equation, the relevant bubble characteristics are the Plateau border radius and a new variable, the effective number of sides. We propose an equation for the individual bubble growth rate as the weighted sum of the growth through bubble-bubble interfaces and through bubble-Plateau borders interfaces. The resulting prediction is successfully tested, without adjustable parameter, using extensive bidimensional Potts model simulations. Simulations also show that a selfsimilar growth regime is observed at any liquid fraction and determine how the average size growth exponent, side number distribution and relative size distribution interpolate between the extreme limits. Applications include concentrated emulsions, grains in polycrystals and other domains with coarsening driven by curvature

PROSTHESIS, TECHNOLOGY AND TRAUMA IN THE MACHINIST FETISHES OF OMA'S VILLA AT BORDEAUX

The paper will look at the historical notion of prosthesis through an analysis of Rem Koolhaas’s 1998 House at Floirac where technology becomes the literal and spiritual generator of the space mediating, through architecture, the uneasy collision between the body and the machine. Organised around a centralised passenger lift for the wheelchair bound owner of the house, and enveloped by the associated family spaces, the house is a highly calibrated architectural object which supplements the body and its internal desires, while at the same time being dependent upon it for its programmatic completion. In the House at Floirac technology is problematised as competing internal and external programmes which a spatial conversation between the sky and ground. The paper will explore the themes embedded in the spatial programme of the House at Floirac by connecting it with the broader theoretical speculations of OMA and a cultural history of prosthetics. Read as an extension of Koolhaas’s gendered observations of the architecture of Manhattan, and eroticised speculations in “Strategy of the Void”, the House at Floirac is evidence of a much deeper strand in OMA’s work through which technology and the body are entwined

USING ALGORITHMS TO ANALYSE THE VISUAL PROPERTIES OF A BUILDING’S STYLE

Residential development within heritage conservation areas is regulated by Development Control Plans (DCP) that provide guidelines about the shape and form that new houses, alterations and additions should take (DIPNR 2004). By understanding that the visual amenity of streets within a city plays an important role in creating a sense of place and community for its citizens (Lynch 1960) they attempt to sustain, through regulation, an urban pattern that has become valued by the community. The visual character of a building within a streetscape is often associated with the style of its construction - a set of visual characteristics that a group of buildings might share. These characteristics include the relationship of the parts of the building to each other, and to the building as a whole, the use of ornament and visible textures, and the scale of elements within the composition. Using algorithms developed within robotic research that enable a computer to interpret a visual environment (similar to those used in medicine and facial recognition for instance), this paper outlines how algorithms can be used to study the visual properties of the built environment. One of the methodological qualities of computer visualisation that makes it so useful for a comparative visual analysis of buildings is that the representational and symbolic meanings of a buildings style play no part. The organisation of the elements can be analysed without having to interpret their possible meaning at the beginning of the process. This paper builds on an established interdisciplinary approach, utilising architectural knowledge and computer visualisation to evaluate the visual character of detached housing within a heritage conservation area. The visual environment is analysed using computer software developed to locate the visual boundaries within a view of a streetscape both as an elevation and aerial view

MEASURING ARCHITECTURE: QUESTIONING THE APPLICATION OF NON-LINEAR MATHEMATICS IN THE ANALYSIS OF HISTORIC BUILDINGS

In the late 1970s the mathematician Benoit Mandelbrot argued that natural systems frequently possess characteristic geometric or visual complexity over multiple scales of observation. This proposition suggests that systems which have evolved over time may exhibit certain local visual qualities that also possess deep structural resonance. In mathematics this observation lead to the formulation of fractal geometry and was central to the rise of the sciences of non-linearity and complexity. During the 1990s a number of researchers developed this concept in relation to architectural design and urban planning and more recently architectural scholars have suggested that such approaches might be used in the analysis of historic buildings. At the heart of this approach, in both its theoretical and computational forms, is a set of processes initially developed by Carl Bovill for analyzing buildings. However, the assumptions implicit in Bovill’s method (itself an extrapolation of an approach proposed by Mandelbrot) have never been adequately questioned. The present paper returns to the origins of Bovill’s analytical method to reconsider his original investigation of key works of 20th century architecture and the way in which Bovill frames images for analysis. The aim of this analysis is to question several assumptions present in Bovill’s method about the way in which computer technology is used to understand the visual qualities of historic buildings

Non-equilibrium Anisotropic Phases, Nucleation and Critical Behavior in a Driven Lennard-Jones Fluid

We describe short-time kinetic and steady-state properties of the non--equilibrium phases, namely, solid, liquid and gas anisotropic phases in a driven Lennard-Jones fluid. This is a computationally-convenient two-dimensional model which exhibits a net current and striped structures at low temperature, thus resembling many situations in nature. We here focus on both critical behavior and details of the nucleation process. In spite of the anisotropy of the late--time spinodal decomposition process, earlier nucleation seems to proceed by Smoluchowski coagulation and Ostwald ripening, which are known to account for nucleation in equilibrium, isotropic lattice systems and actual fluids. On the other hand, a detailed analysis of the system critical behavior rises some intriguing questions on the role of symmetries; this concerns the computer and field-theoretical modeling of non-equilibrium fluids.Comment: 7 pages, 9 ps figures, to appear in PR

A Mean-Field Theory for Coarsening Faceted Surfaces

A mean-field theory is developed for the scale-invariant length distributions observed during the coarsening of one-dimensional faceted surfaces. This theory closely follows the Lifshitz-Slyozov-Wagner theory of Ostwald ripening in two-phase systems [1-3], but the mechanism of coarsening in faceted surfaces requires the addition of convolution terms recalling the work of Smoluchowski [4] and Schumann [5] on coalescence. The model is solved by the exponential distribution, but agreement with experiment is limited by the assumption that neighboring facet lengths are uncorrelated. However, the method concisely describes the essential processes operating in the scaling state, illuminates a clear path for future refinement, and offers a framework for the investigation of faceted surfaces evolving under arbitrary dynamics. [1] I. Lifshitz, V. Slezov, Soviet Physics JETP 38 (1959) 331-339. [2] I. Lifshitz, V. Slyozov, J. Phys. Chem. Solids 19 (1961) 35-50. [3] C. Wagner, Elektrochemie 65 (1961) 581-591. [4] M. von Smoluchowski, Physikalische Zeitschrift 17 (1916) 557-571. [5] T. Schumann, J. Roy. Met. Soc. 66 (1940) 195-207

Nonlinear evolution of surface morphology in InAs/AlAs superlattices via surface diffusion

Continuum simulations of self-organized lateral compositional modulation growth in InAs/AlAs short-period superlattices on InP substrate are presented. Results of the simulations correspond quantitatively to the results of synchrotron x-ray diffraction experiments. The time evolution of the compositional modulation during epitaxial growth can be explained only including a nonlinear dependence of the elastic energy of the growing epitaxial layer on its thickness. From the fit of the experimental data to the growth simulations we have determined the parameters of this nonlinear dependence. It was found that the modulation amplitude don't depend on the values of the surface diffusion constants of particular elements.Comment: 4 pages, 3 figures, published in Phys. Rev. Lett. http://link.aps.org/abstract/PRL/v96/e13610

Utilizing Surface Area to Volume ratios and Thermal Tolerance of Various Bee Species to Predict their Performance under Rising Global Temperatures

The purpose of this research project is to investigate how rising temperatures, for instance climate change, can affect bees of various body sizes given their essential role in the global food supply through pollination of agricultural crops. To achieve this I utilized 3D imaging and 3D modeling techniques to calculate surface area-to-volume (SA/V) ratios of the bees that otherwise cannot be obtained using conventional methods. SA/V ratios were calculated for 4 different families (Halictidae, Colletidae, Apidae, and Megachilidae) in the order Hymenoptera and were analyzed alongside the bee’s Critical Thermal Maximum (CT Max) data, the maximum heat a bee can withstand before losing mobility, to gain insight on the bee's ability to survive in extreme hot temperatures. It is evident from the data that larger bees, characterized by smaller SA/V ratios, presented a higher CT Max suggesting their greater chance of survival in higher temperatures than smaller bees due to less heat exchange relative to their body size. This data implies that with earth’s rising global temperatures larger bees will likely perform better than smaller bees.This poster was presented at the UCSB Center for Science and Engineering Partnerships (CSEP) summer colloquium in 2023

Elastic buckling and optimization of asymmetric i-cross sections of cold-formed thin-walled beams

Subject of the paper includes two open asymmetric I-cross sections of cold-formed thin-walled beams. The both beams are simply supported and are subjects to pure bending. Every I-section is separately described by dimensionless parameters. Geometric properties with warping functions and inertia moments are determined. The strength, global and local stability conditions are defined for both beams. Mathematical solution of elastic local buckling problem for the flange of I-thin-walled beam is experimentally verified. Optimal open cross section shapes of both beams are determined. The optimization criterion is formulated on the basis of a dimensionless objective function. Optimal open cross sections of both beams are compared with a classical I-section beam.У роботі розглядаються холодноформовані тонкостінні двотаврові балки з відкритими асиметричними поперечними перерізами двох типів. Балки вільно оперті та перебувають в умовах чистого згинання. Переріз кожної з балок описують безрозмірними параметрами, що враховують їх геометрію, моменти інерції та деформацію. Визначені умови міцності, локальної та глобальної стійкості для обох типів балок. Проведено експериментальну перевірку отриманого розв’язку задачі про локальну втрату стійкості полиці двотавра. На основі сформульованого критерію оптимізації, з використанням безрозмірної цільової функції, визначено оптимальні форми поперечних перерізів для обох балок. Отримані оптимальні параметри поперечних перерізів порівняно з класичним двотавровим перерізом.В работе рассматриваются холодноформированные тонкостенные двухтавровые балки открытых асимметричных сечений двух типов. Принимается, что балки свободно опертые и находятся в условиях чистого изгиба. Сечения балок описывают безразмерными параметрами, которые учитывают их геометрию, моменты инерции и деформацию. Исследуются параметры прочности, условия локальной и глобальной устойчивости балок. Проведена экспериментальная проверка полученного математического решения задачи о локальной потере устойчивости полки двухтавра. На основании сформулированного критерия оптимизации, с использованием безразмерной функции цели, определены оптимальные формы поперечных сечений балок. Проведено сравнение полученных оптимальных параметров поперечных сечений с классическим двухтавровым сечением