Probabilistic and Distributed Control of a Large-Scale Swarm of Autonomous Agents

We present a novel method for guiding a large-scale swarm of autonomous agents into a desired formation shape in a distributed and scalable manner. Our Probabilistic Swarm Guidance using Inhomogeneous Markov Chains (PSG-IMC) algorithm adopts an Eulerian framework, where the physical space is partitioned into bins and the swarm's density distribution over each bin is controlled. Each agent determines its bin transition probabilities using a time-inhomogeneous Markov chain. These time-varying Markov matrices are constructed by each agent in real-time using the feedback from the current swarm distribution, which is estimated in a distributed manner. The PSG-IMC algorithm minimizes the expected cost of the transitions per time instant, required to achieve and maintain the desired formation shape, even when agents are added to or removed from the swarm. The algorithm scales well with a large number of agents and complex formation shapes, and can also be adapted for area exploration applications. We demonstrate the effectiveness of this proposed swarm guidance algorithm by using results of numerical simulations and hardware experiments with multiple quadrotors.Comment: Submitted to IEEE Transactions on Robotic

Tell Me More: A Creative, Fresh Look at Helping Children and Youth Tell Their Story

Tell Me More. This interactive workshop is designed to both refresh and expand the counseling skills necessary for helping children and youth tell their story. Participants will discuss, explore, and engage in creative, therapeutic techniques that promote the following elements: implementing engaging storytelling, increasing client self-awareness; and fostering a client\u27s sense of being seen, heard, and understood. Stories matter, because they belong to a person

Polarization Switching Dynamics Governed by Thermodynamic Nucleation Process in Ultrathin Ferroelectric Films

A long standing problem of domain switching process - how domains nucleate - is examined in ultrathin ferroelectric films. We demonstrate that the large depolarization fields in ultrathin films could significantly lower the nucleation energy barrier (U*) to a level comparable to thermal energy (kBT), resulting in power-law like polarization decay behaviors. The "Landauer's paradox": U* is thermally insurmountable is not a critical issue in the polarization switching of ultrathin ferroelectric films. We empirically find a universal relation between the polarization decay behavior and U*/kBT.Comment: 5 pages, 4 figure

Direct Separation of Short Range Order in Intermixed Nanocrystalline and Amorphous Phases

Diffraction anomalous fine-structure (DAFS) and extended x-ray absorption fine-structure (EXAFS) measurements were combined to determine short range order (SRO) about a single atomic type in a sample of mixed amorphous and nanocrystalline phases of germanium. EXAFS yields information about the SRO of all Ge atoms in the sample, while DAFS determines the SRO of only the ordered fraction. We determine that the first-shell distance distribution is bimodal; the nanocrystalline distance is the same as the bulk crystal, to within 0.01(2)   Å, but the mean amorphous Ge-Ge bond length is expanded by 0.076(19)   Å. This approach can be applied to many systems of mixed amorphous and nanocrystalline phases

Anisotropic Dirac fermions in a Bi square net of SrMnBi2

We report the highly anisotropic Dirac fermions in a Bi square net of SrMnBi2, based on a first principle calculation, angle resolved photoemission spectroscopy, and quantum oscillations for high-quality single crystals. We found that the Dirac dispersion is generally induced in the (SrBi)+ layer containing a double-sized Bi square net. In contrast to the commonly observed isotropic Dirac cone, the Dirac cone in SrMnBi2 is highly anisotropic with a large momentum-dependent disparity of Fermi velocities of ~ 8. These findings demonstrate that a Bi square net, a common building block of various layered pnictides, provide a new platform that hosts highly anisotropic Dirac fermions.Comment: 5 pages, 4 figure

Observation of inhomogeneous domain nucleation in epitaxial Pb(Zr,Ti)O3 capacitors

We investigated domain nucleation process in epitaxial Pb(Zr,Ti)O3 capacitors under a modified piezoresponse force microscope. We obtained domain evolution images during polarization switching process and observed that domain nucleation occurs at particular sites. This inhomogeneous nucleation process should play an important role in an early stage of switching and under a high electric field. We found that the number of nuclei is linearly proportional to log(switching time), suggesting a broad distribution of activation energies for nucleation. The nucleation sites for a positive bias differ from those for a negative bias, indicating that most nucleation sites are located at ferroelectric/electrode interfaces

Interaction of Salmonella typhimurium and Salmonella enteritidis with polystyrene does not correlate with virulence in young chickens

Salmonella typhimurium and Salmonella enteritidis are the most frequently isolated serotypes in human and animal Salmonella infections. The in vitro surface colonization characteristics of S.typhimurium L1388 and S. enteritidis L1225 on hydrophobic surfaces were assessed with a view tounderstanding their surface preference in relation to in vivo virulence. Although both S. typhimurium and S. enteritidis preferentially colonized polystyrene under normal nutrient-rich growth medium, S.typhimurium formed significantly (P < 0.05: P = 0.000008) smaller amounts of biofilm than S.enteritidis. The biofilm formed on polystyrene was optimum at different times, 200 min and 400 min for S. enteritidis and S. typhimurium, respectively. S. typhimurium also formed significantly (P < 0.05)less biofilm than S. enteritidis when the growth medium was supplemented with 100 mM each ofeither D-(+)-mannose (P = 0.0001), D-(+)-glucose (P = 0.0005), D-(-)-mannitol (P = 0.00002) or xylose (P= 00009). Biofilms formed by S. enteritidis following growth in sugar-supplemented medium were not significantly different from that following growth in non-supplemented medium; but significant (