Configuration Controllability of Simple Mechanical Control Systems

In this paper we present a definition of "configuration controllability" for mechanical systems whose Lagrangian is kinetic energy with respect to a Riemannian metric minus potential energy. A computable test for this new version of controllability is derived. This condition involves an object which we call the symmetric product. Of particular interest is a definition of "equilibrium controllability" for which we are able to derive computable sufficient conditions. Examples illustrate the theory

Configuration Controllability of Simple Mechanical Control Systems

In this paper we present a definition of 'configuration controllability' for mechanical systems whose Lagrangian is kinetic energy with respect to a Riemannian metric minus potential energy. A computable test for this new version of controllability is derived. This condition involves an object that we call the symmetric product. Of particular interest is a definition of 'equilibrium controllability' for which we are able to derive computable sufficient conditions. Examples illustrate the theory

Microbial diversity in the thermal springs within Hot Springs National Park

The thermal water systems of Hot Springs National Park (HSNP) in Hot Springs, Arkansas exist in relative isolation from other North American thermal systems. The HSNP waters could therefore serve as a unique center of thermophilic microbial biodiversity. However, these springs remain largely unexplored using culture-independent next generation sequencing techniques to classify species of thermophilic organisms. Additionally, HSNP has been the focus of anthropogenic development, capping and diverting the springs for use in recreational bathhouse facilities. Human modification of these springs may have impacted the structure of these bacterial communities compared to springs left in a relative natural state. The goal of this study was to compare the community structure in two capped springs and two uncapped springs in HSNP, as well as broadly survey the microbial diversity of the springs. We used Illumina 16S rRNA sequencing of water samples from each spring, the QIIME workflow for sequence analysis, and generated measures of genera and phyla richness, diversity, and evenness. In total, over 700 genera were detected and most individual samples had more than 100 genera. There were also several uncharacterized sequences that could not be placed in known taxa, indicating the sampled springs contain undescribed bacteria. There was great variation both between sites and within samples, so no significant differences were detected in community structure between sites. Our results suggest that these springs, regardless of their human modification, contain a considerable amount of biodiversity, some of it potentially unique to the study site

A field study of placental and fetal lesions associated with bovine abortion

Abortion episodes in cattle were investigated on 54 dairy farms in Cumbria, North Lancashire, and North Yorkshire from 1984 to 1986. From a breeding" population of approximately 3600 dairy cows 149 abortions were investigated, representing an annual abortion rate of 2%, substantially higher than previously reported national estimates.Visits were made by a Local Veterinary Inspector of the Ministry of Agriculture, Fisheries, and Food to each farm reporting an abortion, under the Brucellosis Order (England and Wales) 1978. The required samples were submitted to a Veterinary Investigation Centre (V.I.C), accompanied by form BS7. In addition, further samples were taken from each case where possible; placentome, fetal placenta, clotted blood (followed by a convalescent sample 28 days later), and fetus. All were examined in the practice laboratory.Routine bacteriology was carried out on fetal stomach contents, lung, and placentome/placenta; cultured bacteria were identified. Fetal thoracic fluid and paired serum samples were sent to a V.I.C. for serological examination against Bovine Viral Diarrhoea virus (B.V.D), Infectious Bovine Rhino-tracheitis virus (I.B.R), and Leptospira hard.jo infections.Pathological studies were made on all fetal and placental material collected. Gross lesions were noted. Eyelid, heart, lungs, liver, and placental tissues were routinely fixed in 10% formalin, sectioned, stained with Haematoxylin and Eosin, and examined.Autolysis was present in 81 of 118 fetuses examined. Gross lesions were seen in 96 fetuses and 66 placental tissues. Except for hepatomegaly (3 cases), they were not considered to be diagnostically significance. Seven fetuses were mummified.Immunoglobulins IgG and IgM were found in 35/129 fetuses, as well as titres to B.V.D (13/35), and L. hard.jo (5/35). Positive titres to B.V.D, I.B.R, and L. hard.jo were present in paired serum from 62 cows.Histological lesions were demonstrated in tissue from 113 abortions; infection was associated with 57 episodes. In 9 cases which remained undiagnosed, consistent lesions of conjunctival hyperplasia with a coexisting placentitis (6/9) and amnionitis (2/9) were recorded, resembling experimental fetal infection with Ureaplasma diversum.Myocarditis was associated with B.V.D (6 cases) and I.B.R (5 cases), which often coexisted with interstitial pneumonia (13 cases). Bronchial pneumonia occurred in 24 fetuses, associated with isolation of pure bacterial cultures from the lung. Erythroblastosis featured in 8 abortuses where L.hardjo infection was present.Placentome was a diagnostically significant tissue; 18/40 presented a necrotic placentitis. Haemorrhagic lesions were found in 20, frequently linked to L.hardjo infection, but accompanied by hypoxic change

Intermittent Connectivity for Exploration in Communication-Constrained Multi-Agent Systems

Motivated by exploration of communication-constrained underground environments using robot teams, we study the problem of planning for intermittent connectivity in multi-agent systems. We propose a novel concept of information-consistency to handle situations where the plan is not initially known by all agents, and suggest an integer linear program for synthesizing information-consistent plans that also achieve auxiliary goals. Furthermore, inspired by network flow problems we propose a novel way to pose connectivity constraints that scales much better than previous methods. In the second part of the paper we apply these results in an exploration setting, and propose a clustering method that separates a large exploration problem into smaller problems that can be solved independently. We demonstrate how the resulting exploration algorithm is able to coordinate a team of ten agents to explore a large environment

Modelling and experimental investigation of carangiform locomotion for control

We propose a model for planar carangiform swimming based on conservative equations for the interaction of a rigid body and an incompressible fluid. We account for the generation of thrust due to vortex shedding through controlled coupling terms. We investigate the correct form of this coupling experimentally with a robotic propulsor, comparing its observed behavior to that predicted by unsteady hydrodynamics. Our analysis of thrust generation by an oscillating hydrofoil allows us to characterize and evaluate certain families of gaits. Our final swimming model takes the form of a control-affine nonlinear system

Geometric control of particle manipulation in a two-dimensional fluid

Manipulation of particles suspended in fluids is crucial for many applications, such as precision machining, chemical processes, bio-engineering, and self-feeding of microorganisms. In this paper, we study the problem of particle manipulation by cyclic fluid boundary excitations from a geometric-control viewpoint. We focus on the simplified problem of manipulating a single particle by generating controlled cyclic motion of a circular rigid body in a two-dimensional perfect fluid. We show that the drift in the particle location after one cyclic motion of the body can be interpreted as the geometric phase of a connection induced by the system's hydrodynamics. We then formulate the problem as a control system, and derive a geometric criterion for its nonlinear controllability. Moreover, by exploiting the geometric structure of the system, we explicitly construct a feedback-based gait that results in attraction of the particle towards the rigid body. We argue that our gait is robust and model-independent, and demonstrate it in both perfect fluid and Stokes fluid

Configuration Controllability of Simple Mechanical Control Systems

In this paper we present a definition of "configuration controllability" for mechanical systems whose Lagrangian is kinetic energy with respect to a Riemannian metric minus potential energy. A computable test for this new version of controllability is also derived. This condition involves a new object which we call the {\em symmetric product}. Of particular interest is a definition of "equilibrium controllability" for which we are able to derive computable sufficient conditions. Examples illustrate the theory