946 research outputs found

    Pose consensus based on dual quaternion algebra with application to decentralized formation control of mobile manipulators

    Full text link
    This paper presents a solution based on dual quaternion algebra to the general problem of pose (i.e., position and orientation) consensus for systems composed of multiple rigid-bodies. The dual quaternion algebra is used to model the agents' poses and also in the distributed control laws, making the proposed technique easily applicable to time-varying formation control of general robotic systems. The proposed pose consensus protocol has guaranteed convergence when the interaction among the agents is represented by directed graphs with directed spanning trees, which is a more general result when compared to the literature on formation control. In order to illustrate the proposed pose consensus protocol and its extension to the problem of formation control, we present a numerical simulation with a large number of free-flying agents and also an application of cooperative manipulation by using real mobile manipulators

    Viroids of grapevines in Italy

    Get PDF
    Rebviroide in ItalienEs wird über das Vorkommen niedermolekularer RNAs bei 48 Vitis-vinifera-Stämmen und 15 amerikanischen Vitis-Arten und Kreuzungen aus Italien, Osteuropa, Mittelmeer- und Nahost-Ländern berichtet. In den Sämlingen zweier Sorten wurden keine derartigen RNAs gefunden. Aufgrund ihres elektrophoretischen Verhaltens wurden diese RNAs vorläufig identifiziert als Grapevine yellow speckle-Viroid (GYSVd), Grapeivine-Viroid 2 (GVd2) und Hop stunt-Viroid (HSVd). Das letztere Viroid löste bei künstlich infizierten Pflanzen von Tomate cv. Rutgers und Gurke cv. Suyo Befallssymptome aus. HSVd, GYSVd und GVd2 wurden in 97, 92 bzw. 11 % der untersuchten Proben wiedergefunden. In der Regel lagen Mischinfektionen vor, wobei die Kombination von HSVd mit GYSVd überwog. Diese beiden Viroide kamen regelmäßig in Reben mit den Symptomen von Yellow speckle oder Vein banding vor. Es wurde keine eindeutige Beziehung zwischen dem Vorkommen eines der Viroide und Rebkrankheiten mit unklarer Ätiologie, wie Vein necrosis oder Fleck, gefunden

    Identification of the agent of grapevine fleck disease

    Get PDF
    An antiserum against an Italian isolate of grapevine phloem-limited isometric virus (GPLIV) was used in an ELISA survey carried out for assessing the natural distribution of the virus and its association with fleck disease. A total of 591 vines of Vitis rupestris were checked for the presence of GPLIV. Of 150 plants with fleck symptoms, 138 (92 %) were ELISA-positive and 12 (8 %) negative. Of 441 symptomless V. rupestris, 435 (98,6 %) were ELISA-negative and 6 (1,4 %) positive for GPLIV. The virus was detected in about 30 % of 694 vines of different origin grown in Apulia (Southern Italy). The highest infection (53 %) was in a commercial vineyard of cv. Italia and the lowest (8 %) in a plot of certified and visually selected rootstocks. Fleck-infected, but not fleck-free V. rupestris contained virus particles and vesiculated inclusion bodies in phloem tissues. LN 33 plantlets derived from in vitro culture of meristem tips from ELISA-positive fleck-infected mother plants were found to be free from GPLIV, as ascertained by ELISA and thin-sectioning. These vines failed to induce fleck symptoms when grafted on V. rupestris. It is concluded that GPLIV is the agent of fleck and, therefore, it should be renamed grapevine fleck virus (GFKV)

    Serological detection of Grapevine rupestris stem pitting-associated virus (GRSPa V) by a polyclonal antiserum to recombinant virus coat protein

    Get PDF
    The coat protein gene of Grapevine rupestris stem pitting-associated virus (GRSPaV) was amplified with primers based on the completely sequenced Californian GRSPaV isolate, The protein expressed in Escherichia coli was used to raise an antiserum in rabbit. This antiserum was successfully used to detect virus coat protein in infected grapevine extracts either spotted on polyvinyl difluoride membranes (dot immunobinding) or blotted on membranes after gel separation (Western blot). The antiserum titre was 1:5,000 in Western blot. GRSPaV was detected in leaf petioles and cortical scrapings from dormant canes during the whole vegetative season. Several accessions of Vitis rupestris, currently used as presumptive virus-free indicators of Rupestris stem pitting, were found to be infected by this virus. While the application of the antiserum in ELISA was ineffective, the availability of similarly simple and effective serological tools, such as dot immunobinding, may allow a wide survey for GRSPaV

    Changing the approach to sustainable constructions: An adaptive mix-design calibration process for earth composite materials

    Get PDF
    One major drawback of excavation earth-based composite construction materials is the variability in excavation earth characteristics from site to site. This variability can affect certain physical properties, and, in turn, the design models used to create a structure. To solve this problem, a methodology has been developed to predict the physical properties of earth-based composites for any mix-design variation, which enables a robust structural design process. This new methodology has been tested for Shot-earth, a new class of earth-based composite material made using high rates of excavation earth, aggregates, and a low rate of stabilization if needed. Shot-earth is placed using a high-speed dry-mix process. The methodology was tested by preparing small, inexpensive specimens through a process that simulates the dry-process used to fabricate Shot-earth in the field. An adaptive technique, used in conjunction with the experimental methodology, allows for the identification of the variant of possible Shot-earth mix-designs that provides optimal physical properties for a specific project. This technique is potentially applicable to any type of earth-based composite. The proposed methodology’s reliability enables a fast and cost-effective detailing of Shot-earth constructions
    corecore