Internal agent states : experiments using the swarm leader concept

In recent years, an understanding of the operating principles and stability of natural swarms has proven to be a useful tool for the design and control of artificial robotic agents. Many robotic systems, whose design or control principals are inspired by behavioural aspects of real biological systems such as leader-follower relationship, have been developed. We introduced an algorithm which successfully enhances the navigation performance of a swarm of robots using the swarm leader concept. This paper presents some applications based on that work using the simulations and experimental implementation using a swarming behaviour test-bed at the University of Strathclyde. Experimental and simulation results match closely in a way that confirms the efficiency of the algorithm as well as its applicability

Formation Control of Robotic Swarm Using Bounded Artificial Forces

Formation control of multirobot systems has drawn significant attention in the recent years. This paper presents a potential field control algorithm, navigating a swarm of robots into a predefined 2D shape while avoiding intermember collisions. The algorithm applies in both stationary and moving targets formation. We define the bounded artificial forces in the form of exponential functions, so that the behavior of the swarm drove by the forces can be adjusted via selecting proper control parameters. The theoretical analysis of the swarm behavior proves the stability and convergence properties of the algorithm. We further make certain modifications upon the forces to improve the robustness of the swarm behavior in the presence of realistic implementation considerations. The considerations include obstacle avoidance, local minima, and deformation of the shape. Finally, detailed simulation results validate the efficiency of the proposed algorithm, and the direction of possible futrue work is discussed in the conclusions

Novel food grade dispersants : review of recent progress

Many foreseen advances in the design of food structures, suitable for ever demanding nutrient delivery systems, tailored controlled release, microencapsulation and protection of active ingredients, require a generation of superior dispersants than those currently provided by proteins. While the most efficient structure for such dispersants is relatively easy to specify, in foods they cannot simply be synthetically manufactured. The review highlights several possible strategies for realising more efficient food colloid stabilisers and summarises the key recent progress for each approach, both experimentally and theoretically. The emphasis is on those methods that lead to macromolecularly adsorbed layers. Practical aspects apart, we also discuss a number of interesting fundamental questions that each approach raises

Recent Advances in Multi Robot Systems

To design a team of robots which is able to perform given tasks is a great concern of many members of robotics community. There are many problems left to be solved in order to have the fully functional robot team. Robotics community is trying hard to solve such problems (navigation, task allocation, communication, adaptation, control, ...). This book represents the contributions of the top researchers in this field and will serve as a valuable tool for professionals in this interdisciplinary field. It is focused on the challenging issues of team architectures, vehicle learning and adaptation, heterogeneous group control and cooperation, task selection, dynamic autonomy, mixed initiative, and human and robot team interaction. The book consists of 16 chapters introducing both basic research and advanced developments. Topics covered include kinematics, dynamic analysis, accuracy, optimization design, modelling, simulation and control of multi robot systems

Topological Self-Organisation: Using a particle-spring system simulation to generate structural space-filling lattices

The problem being addressed relates to the filling of a certain volume with a structural space frame network lattice consisting of a given number of nodes. A method is proposed that comprises a generative algorithm including a physical dynamic simulation of particle-spring system. The algorithm is able to arrange nodes in space and establish connections among them through local rules of self-organisation, thus producing space frame topologies. In order to determine the appropriateness of the method, an experiment is conducted that involves testing the algorithm in the case of filling the volume of a cube with multiple numbers of nodes. The geometrical, topological and structural aspects of the generated lattices are analysed and discussed. The results indicate that the method is capable of generating efficient space frame topologies that fill spatial envelopes

Forces between agglutinated bacteria

Thesis (M.A.)--Boston University, 1945. This item was digitized by the Internet Archive

Silver nanostructures: chemical synthesis of colloids and composites nanoparticles, plamon resonance properties and silver nanoparticles monolayer films prepared by spin-coating

El presente trabajo tiene como objetivo desarrollar en solución acuosa y a tem-peratura ambiente, rutas de síntesis química coloidal de nanopartículas de plata y nano-partículas compuestas estables. Se obtienen nanopartículas de plata reproducibles, con un control morfológico de tamaño y forma durante el proceso de síntesis. Llevamos a cabo el estudio de las propiedades ópticas (espectros de absorción de las resonancias de plasmones superficiales (SPR)) que caracterizan a una determinada forma y tamaño. El análisis incluye estructuras nanométricas de plata de diferentes tamaños, en ambientes diversos y formas diferentes, como esferas, prolates, y prismas de diferente sección transversal, etc Se ha demostrado que la síntesis química produce coloides de nanopartículas de plata esféricas y anisotrópicas estables. La morfología y estabilidad de las nanopartícu-las coloidales son estudiadas mediante técnicas de espectroscopia y microscopía elec-trónica. El rol y concentración necesaria de cada uno de los reactivos para producir co-loides estables mediante síntesis química son determinadas. Se ha demostrado que, con-trariamente a las opiniones actualmente expresadas en la literatura, es posible controlar el tamaño de las nanopartículas de plata y obtener coloides de nanopartículas de plata esféricas y anisotrópicas estables por largo tiempo, utilizando una ruta de síntesis quí-mica sencilla y una baja concentración de reactivos estabilizadores (PVP). Recubrimientos de nanopartículas esféricas de plata estabilizadas con polivinilpirroli-dona (PVP) sobre substratos de vidrio óptico son preparados mediante el proceso de spin-coating y un posterior tratamiento térmico. Diferentes morfologías tipo core-shell de Ag@SiO2 son preparados mediante un método químico simple y rápido, sin necesidad de adicionar reactivos de acoplamiento o modificadores superficiales de la sílice. Proponemos mecanismos de reacción para la preparación de diferentes nano-estructuras tipo core-shell de plata-sílice. Las nanopartí-culas compuestas de sílice-plata muestran unas propiedades de absorción de resonancia plasmónica muy evidentes. El trabajo de éste capítulo ha sido realizado en colaboración con Juan C. Flores, quien desarrolló la ruta de síntesis como parte de sus estudios de doctorado. Por último, una modificación del método sol-gel es empleada para la prepara-ción de nanopartículas de TiO2, y partículas compuestas de Ag@TiO2, SiO2@TiO2-Ag y SiO2@Ag@TiO2. Diferentes morfologías tipo core-shell son preparadas mediante un método químico simple y rápido sobre un substrato óxido, sin necesidad de adicionar agentes de acoplamiento o modificaciones superficiales. Las evidentes propiedades de absorción plasmónica de las nanopartículas de plata mostradas por las partículas com-puestas han demostrado la presencia de plata metálica sobre la titania, sin la posterior oxidación de la capa de plata por el contacto directo con la titania (TiO2). Esta evidencia es confirmada por la técnica de microscopía electrónica de alta resolución. Las propie-dades de absorción plasmónica de las partículas compuestas hacen a estos materiales muy prometedores para aplicaciones foto-catalíticas.The present work aims to develop chemical synthesis routes of stable colloidal silver nanoparticles and composites nanoparticles in aqueous solution at room tempera-ture. We obtain reproducible morphological control of silver nanoparticles size and shape during synthesis solely by solution chemistry and carry out the study of the opti-cal properties (surface plasmon resonances (RPS) absorption spectra) which character-ize a specific shape and size. The analysis includes silver nanosized bodies of different size, in diverse environments and of various shapes, as spheres, prolates, and prisms of different transversal section, etc. Synthetic wet chemistry routes yielding stable colloids of spherical and aniso-tropic silver nanoparticles are demonstrated, and the morphology and stability of the colloidal nanoparticles studied extensively through spectroscopy and electron micros-copy techniques. The role of each reagent and the concentrations required to obtain sta-ble colloid via these wet chemical routes is determined. It was shown that, contrary to commonly expressed opinions in the literature, it is possible to control the particle size of silver nanoparticles and obtain long-term sable colloids of both spherical and aniso-tropic silver nanoparticles using simple chemical routes and low concentration of stabi-lizing agent (PVP). Films of polyvinylpyrrolidone (PVP) stabilized spherical silver nanoparticles are also prepared, by using spin coating on standard optical glass plates and subsequent thermal processing. Different core-shell type morphologies of Ag@SiO2 are also produced using a simple and rapid chemical method, without using added coupling agents or surface modifications of silica. We propose reaction mechanisms for the formation of the dif-ferent silica-silver core-shell nanostructures. The silica-silver composite nanoparticle display clear plasmonic resonance absorption properties. This chapter work has been done in collaboration with PhD student Juan C. Flores who developed the synthesis route as part of his doctoral studies. Finally, a sol-gel chemistry approach was used to fabricate nanoparticles in the systems TiO2, Ag@TiO2, Ag@TiO2-SiO2 and TiO2@Ag@SiO2. Different core-shell morphologies are produced using a simple and rapid chemical method. without using added coupling agents or surface modifications of the oxide substrate. Clear silver na-noparticle plasmonic absorption properties shown by the composite nanoparticles demonstrate the formation of metallic Ag, without the oxidation of Ag nanoshell in di-rect contact with TiO2, evidence confirmed also by high resolution electron microscopy. The plasmonic absorption properties of the composites nanoparticles make them a promising material for photocatalytic applications

Synthesis and characterization of highly stable functional silica nanoparticles for LbL assembly

Layer by Layer (LbL) assembly is a superior method to create thin films with aqueous based dispersions which include polyelectrolytes and nanoparticles. LbL presents exceptional advantages like conformal coatings with controlled structure and composition by using electrostatic interactions of oppositely charged materials. Nevertheless, these interactions may cause weaker mechanical properties on the thin films. In order to eliminate the drawback, the covalent bond between oppositely charged materials can establish by crosslinking of functional groups. Silica nanoparticles are mostly used in the LbL process due to enhance adhesion of films by creating roughness on the surface. They are also suitable for surface modification which provides surface charge manipulation, stable dispersibility and good mechanical property. Silane alkoxy groups are one of the best choices for functionalization process. These coupling agents promote mechanical robustness of the surface via the formation of physically and chemically stable covalent bonds. In this study, silica nanoparticle was synthesized by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) in surfactant/cyclohexane/ammonia media by microemulsion method. Monodisperse and having around 50 nm diameter silica nanoparticles were achieved to use in further steps. Amino and poly (ethylene glycol)-terminated alkoxy silanes were performed to ensure positive and negative surface charges on the silica nanoparticles surface by crosslinking. The functionalized silica nanoparticles were utilized in LbL process, right after poly allylamine hydrochloride (PAH) and poly (sodium 4-styrenesulfonate) (SPS) were applied in desired number of layers on the silicon wafer substrates. Dynamic light scattering (DLS) is employed to analyze size and surface charge distribution of bare and functionalized silica nanoparticles. The presence of functional groups was examined by Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR). The thickness, surface topography and roughness of thin films are measured by ellipsometry and atomic force microscopy (AFM). Scanning electron microscopy (SEM) was performed to analyze nanostructural morphology of silica nanoparticle and thin films. The obtained results indicated that chemically crosslinked silica nanoparticle containing thin films exhibit better mechanical properties that make them useful for desired applications

Investigation of New Forward Osmosis Draw Agents and Prioritization of Recent Developments of Draw Agents Using Multi-criteria Decision Analysis

Forward osmosis (FO) is an emerging technology for water treatment due to their ability to draw freshwater using an osmotic pressure gradient across a semi-permeable membrane. However, the lack of draw agents that could both produce reasonable flux and be separated from the draw solution at a low cost stand in the way of widespread implementation. This study had two objectives: evaluate the performance of three materials — peptone, carboxymethyl cellulose (CMC), and magnetite nanoparticles (Fe3O4 NPs) — as potential draw agents, and to use multi-criteria decision matrices to systematically prioritize known draw agents from literature for research investigation. Peptone showed water flux and reverse solute flux values comparable to other organic draw agents. CMC’s high viscosity made it impractical to use and is not recommended as a draw agent. Fe3O4 NPs showed average low fluxes (e.g., 2.14 LMH) but discrete occurrences of high flux values (e.g., 14 LMH) were observed during FO tests. This result indicates that these nanoparticles have potential as draw agents but further work is needed to optimize the characteristics of the nanoparticle suspension. Separation of the nanoparticles from the product water using coagulation was shown to be theoretically possible if only electrostatic and van der Waals forces are taken into account, not steric repulsion. If coagulation is to be considered for separation, research efforts on development of nanoparticle suspensions as FO draw agents should focus on development of electrostatically stabilized nanoparticles. A combination of Fe3O4 NP and peptone showed a higher flux than Fe3O4 NPs alone, but did not produce additive or synergistic flux. This warrants further research to investigate more combinations of draw agents to achieve higher flux than that obtained by individual draw agents. Potential draw agents were prioritized by conducting a literature review of draw agents, extracting data on evaluation criteria for draw agents developed over the past five years, using these data to rank the draw agents using the Analytical Hierarchy Process (AHP) and Technique for Order of Preference by Similarity to Ideal Solutions (TOPSIS). The evaluation criteria used in the ranking matrices were water flux, reverse solute flux, replenishment cost, regeneration cost, and regeneration efficacy. The results showed that the top five ranked draw agents were P-2SO3-2Na, TPHMP-Na, PEI-600P-Na, NaCl, and NH4-CO2. The impact of the assumption made during the multi-criteria decision analysis process was evaluated through sensitivity analyses altering criterion weighting and including more criteria. This ranking system provided recommendations for future research and development on draw agents by highlighting research gaps

Rational design and investigation of polypeptide multilayer films and capsules

Three major concerns in the science of materials today are control over structure and function at the molecular level, biodegradability, and scalability of production. Polymeric materials, notably polyelectrolyte multilayer films, have shown considerable promise in all these areas, and for rational development of multifunctionality. Polypeptides constitute an especially interesting class of polyelectrolyte, given their inherent biodegradability, means of control over structure, methods of large-scale synthesis, and ability to encode biological information. Relatively little is known, however, about polypeptide multilayer films, despite recent advances in the general area. In this dissertation, ten heteropolypeptides were designed and synthesized by Fmoc chemistry. These peptides and homopolypeptides available from a commercial source have been used to carry out a systematic study of the physical basis of polypeptide multilayer film assembly, structure, and stability, in order to gain a greater grasp of the roles of different kinds of non-covalent interaction, degree of polymerization, and polydispersity. The data show that amino acid composition, sequence, and specific combination of anionic and cationic polypeptides together determine film growth behavior, secondary structure content, overall density, surface morphology, and susceptibility to environmental perturbations. The peptides are largely unstructured in solution but tend to form β sheets in a multilayer film at neutral pH. Electrostatic interactions dominate polypeptide adsorption and film stability, but hydrophobic interactions and hydrogen bonding have a significant influence on internal structure and surface morphology, decreasing film density and increasing film thickness and roughness. Experimental results of polypeptide multilayer films correlate well with molecular dynamics (MD) simulation results of interpolyelectrolyte complexes (IPECs) of the same polypeptide designs. Microcrystals of pyrene, a hydrophobic model drug, have been encapsulated by the polypeptides used in film study. The drug release kinetics have been found to depend on precoating material, polypeptide structure, and microcapsule architecture. The results of this dissertation will inform materials science, studies of polyelectrolyte multilayer films and micro/nanocapsules, and protein folding. In particular, this work will help to provide a foundation for the engineering of novel peptide-based biomaterials for a variety of purposes, such as enantiomeric separations, antimicrobial films, artificial skin grafts, cell and tissue culture, biodegradable implant coatings, artificial cells and drug delivery systems