7,125 research outputs found
An Algorithm for Computing Four-Ramond Vertices at Arbitrary Level
We perform the sewing of two (dual) Ramond reggeon vertices and derive an
algorithm by means of which the so obtained four-Ramond reggeon vertex may be
explicitly computed at arbitrary oscillator (mass) level. A closed form of the
four-vertex is then deduced on the basis of a comparison to all terms obtained
by sewing that contain only level zero and one oscillators. Results are
presented for both complex fermions and for the previously studied case of real
fermions.Comment: 31 pages, Latex, Goteborg ITP 92-5
The Twisted String Vertex Algorithm Applied to the -Twisted Scalar String Four Vertex
Recently an algorithm was found by means of which one can calculate terms at
arbitrary oscillator level in the four-Ramond vertex obtained by sewing. Here
we show that this algorithm is applicable also to the case of -twisted scalars and derive the full propagator for scalars on the Riemann
sphere with two branch cuts. The relation to similar results previously derived
in the literature by other means is discussed briefly.Comment: 18 pages (LaTeX), G\"oteborg ITP 94-
Connected component identification and cluster update on GPU
Cluster identification tasks occur in a multitude of contexts in physics and
engineering such as, for instance, cluster algorithms for simulating spin
models, percolation simulations, segmentation problems in image processing, or
network analysis. While it has been shown that graphics processing units (GPUs)
can result in speedups of two to three orders of magnitude as compared to
serial codes on CPUs for the case of local and thus naturally parallelized
problems such as single-spin flip update simulations of spin models, the
situation is considerably more complicated for the non-local problem of cluster
or connected component identification. I discuss the suitability of different
approaches of parallelization of cluster labeling and cluster update algorithms
for calculations on GPU and compare to the performance of serial
implementations.Comment: 15 pages, 14 figures, one table, submitted to PR
A Multi-Robot Cooperation Framework for Sewing Personalized Stent Grafts
This paper presents a multi-robot system for manufacturing personalized
medical stent grafts. The proposed system adopts a modular design, which
includes: a (personalized) mandrel module, a bimanual sewing module, and a
vision module. The mandrel module incorporates the personalized geometry of
patients, while the bimanual sewing module adopts a learning-by-demonstration
approach to transfer human hand-sewing skills to the robots. The human
demonstrations were firstly observed by the vision module and then encoded
using a statistical model to generate the reference motion trajectories. During
autonomous robot sewing, the vision module plays the role of coordinating
multi-robot collaboration. Experiment results show that the robots can adapt to
generalized stent designs. The proposed system can also be used for other
manipulation tasks, especially for flexible production of customized products
and where bimanual or multi-robot cooperation is required.Comment: 10 pages, 12 figures, accepted by IEEE Transactions on Industrial
Informatics, Key words: modularity, medical device customization, multi-robot
system, robot learning, visual servoing, robot sewin
A Multi-Robot Cooperation Framework for Sewing Personalized Stent Grafts
This paper presents a multi-robot system for manufacturing personalized
medical stent grafts. The proposed system adopts a modular design, which
includes: a (personalized) mandrel module, a bimanual sewing module, and a
vision module. The mandrel module incorporates the personalized geometry of
patients, while the bimanual sewing module adopts a learning-by-demonstration
approach to transfer human hand-sewing skills to the robots. The human
demonstrations were firstly observed by the vision module and then encoded
using a statistical model to generate the reference motion trajectories. During
autonomous robot sewing, the vision module plays the role of coordinating
multi-robot collaboration. Experiment results show that the robots can adapt to
generalized stent designs. The proposed system can also be used for other
manipulation tasks, especially for flexible production of customized products
and where bimanual or multi-robot cooperation is required.Comment: 10 pages, 12 figures, accepted by IEEE Transactions on Industrial
Informatics, Key words: modularity, medical device customization, multi-robot
system, robot learning, visual servoing, robot sewin
Simplicial Nonlinear Principal Component Analysis
We present a new manifold learning algorithm that takes a set of data points
lying on or near a lower dimensional manifold as input, possibly with noise,
and outputs a simplicial complex that fits the data and the manifold. We have
implemented the algorithm in the case where the input data can be triangulated.
We provide triangulations of data sets that fall on the surface of a torus,
sphere, swiss roll, and creased sheet embedded in a fifty dimensional space. We
also discuss the theoretical justification of our algorithm.Comment: 21 pages, 6 figure
Fuzzy logic based control strategies for an electromagnetic actuated sewing machine presser foot
Comunicação apresentada na International Conference on Industrial Technology, Hammamet, Tunisia, 8 - 10 Dezembro 2004.Industrial sewing machines have been significantly improved in recent years and especially electronic sewing control is now being introduced. This study concerns the development of a controller for an electromagnetically actuated presser foot. The controller is responsible for controlling the vertical movement of the presser foot. This is an important point since the presser foot tends to bounce at high sewing speeds, resulting in irregular seams. In this study a fuzzy logic controller was used. The reference displacement value is set up by an adaptive method in order to respect changes on the number of plies. The tested fuzzy logic controller allows a better performance of the control especially in relation with different fabrics. During this study another control strategy was considered. This control strategy combines a PI-algorithm with a fuzzy logic controller. Yet, the controller restricts the use of new fabrics, which have not been defined in advance. This aspect will be a major point in the future development in order to recognize the fabrics during sewing and to adapt the controller adequately.(undefined
- …