3,347 research outputs found
Optimal control design for robust fuzzy friction compensation in a robot joint
This paper presents a methodology for the compensation of nonlinear friction in a robot joint structure based on a fuzzy local modeling technique. To enhance the tracking performance of the robot joint, a dynamic model is derived from the local physical properties of friction. The model is the basis of a precompensator taking into account the dynamics of the overall corrected system by means of a minor loop. The proposed structure does not claim to faithfully reproduce complex phenomena driven by friction. However, the linearity of the local models simplifies the design and implementation of the observer, and its estimation capabilities are improved by the nonlinear integral gain. The controller can then be robustly synthesized using linear matrix inequalities to cancel the effects of inexact friction compensation. Experimental tests conducted on a robot joint with a high level of friction demonstrate the effectiveness of the proposed fuzzy observer-based control strategy for tracking system trajectories when operating in zero-velocity regions and during motion reversals
D-brane Categories for Orientifolds -- The Landau-Ginzburg Case
We construct and classify categories of D-branes in orientifolds based on
Landau-Ginzburg models and their orbifolds. Consistency of the worldsheet
parity action on the matrix factorizations plays the key role. This provides
all the requisite data for an orientifold construction after embedding in
string theory. One of our main results is a computation of topological field
theory correlators on unoriented worldsheets, generalizing the formulas of Vafa
and Kapustin-Li for oriented worldsheets, as well as the extension of these
results to orbifolds. We also find a doubling of Knoerrer periodicity in the
orientifold context.Comment: 45 pages, 6 figure
Quiver Theories from D6-branes via Mirror Symmetry
We study N=1 four dimensional quiver theories arising on the worldvolume of
D3-branes at del Pezzo singularities of Calabi-Yau threefolds. We argue that
under local mirror symmetry D3-branes become D6-branes wrapped on a three torus
in the mirror manifold. The type IIB (p,q) 5-brane web description of the local
del Pezzo, being closely related to the geometry of its mirror manifold,
encodes the geometry of 3-cycles and is used to obtain gauge groups, quiver
diagrams and the charges of the fractional branes.Comment: 30 pages, citations adde
Multiobjective control of a vehicle with triple trailers
We consider the backing-up control of a vehicle with triple trailers using a model-based fuzzy-control methodology. First, the vehicle model is represented by a Takagi-Sugeno fuzzy model. Then, we employ the so-called "parallel distributed compensation" design to arrive at a controller that guarantees the stability of the closed-loop system consisted of the fuzzy model and controller. The control-design problem is cast in terms of linear matrix inequalities (LMIs). In addition to stability, the control performance considerations such as decay rate, constraints on input and output, and disturbance rejection are incorporated in the LMI conditions. In application to the vehicle with triple trailers setup, we utilize these LMI conditions to explicitly avoid the saturation of the steering angle and the jackknife phenomenon in the control design. Both simulation and experimental results are presented. Our results demonstrate that the fuzzy controller effectively achieves the backing-up control of the vehicle with triple trailers while avoiding the saturation of the actuator and "jackknife" phenomenon
Automated Model Construction for Seismic Disaster Assessment of Pipeline Network in Wide Urban Area
This chapter is on rational seismic damage assessment over a wide area through the development of a module for the automated model construction of a pipeline network of lifelines using geographic information system (GIS) data. The module is assigned a functionality that can generate a simple one-dimensional line model and a two-dimensional surface model with high fidelity for the pipe shape. The source code of the module is written in object-oriented programming in order to make it easier to extend it to generate other analysis models. The module was applied to the actual GIS, and the shape of the output model was verified. Numerical analysis was performed on the output of the module, and it showed that the automatically constructed model is mechanically valid and can be used for seismic response analysis
Effects of Teaching a Questioning Strategy on Reading Comprehension of Learning Disabled Adolescents
This research was published by the KU Center for Research on Learning, formerly known as the University of Kansas Institute for Research in Learning Disabilities.Nine junior high learning disabled students received a Questioning Treatment and an equivalent Control Group received traditional reading training. The results of this study confirmed the hypothesis that training a questioning strategy is an effective method to increase reading comprehension performance as measured by a formal reading test. No significant relationship was found between questioning frequency levels and reading comprehension performance, and no significant interaction occurred between training conditions and questioning frequency levels
Hemoglobin genotype has minimal influence on the physiological response of juvenile atlantic cod (Gadus morhua) to environmental challenges
Hemoglobin (Hb) polymorphism in cod is associated with temperatureârelated differences in biogeographical distribution, and several authors have suggested that functional characteristics of the various hemoglobin isoforms (HbIs) directly influence phenotypic traits such as growth rate. However, no study has directly examined whether Hb genotype translates into physiological differences at the whole animal level. Thus, we generated a family of juvenile Atlantic cod consisting of all three main Hb genotypes (HbIâ1/1, HbIâ2/2, and HbIâ1/2) by crossing a single pair of heterozygous parents, and we compared their metabolic and cortisol responses to an acute thermal challenge (10°C to their critical thermal maximum [CTM] or 22°C, respectively) and tolerance of graded hypoxia. There were no differences in routine metabolism (at 10°C), maximum metabolic rate, metabolic scope, CTM (overall mean 22.9° ± 0.2°C), or resting and poststress plasma cortisol levels among Hb genotypes. Further, although the HbIâ1/1 fish grew more (by 15%–30% during the first 9 mo) when reared at 10° ± 1°C and had a slightly enhanced hypoxia tolerance at 10°C (e.g., the critical O2 levels for HbIâ1/1, HbIâ2/2, and HbIâ1/2 cod were 35.56% ± 1.24%, and 40.20% ± 1.99% air saturation, respectively), these results are contradictory to expectations based on HbI functional properties. Thus, our findings (1) do not support previous assumptions that growth rate differences among cod Hb genotypes result from a more efficient use of the oxygen supply—that is, reduced standard metabolic rates and/or increased metabolic capacity—and (2) suggest that in juvenile cod, there is no selective advantage to having a particular Hb genotype with regards to the capacity to withstand ecologically relevant environmental challenges.<br /
First observation of two hyperfine transitions in antiprotonic He-3
We report on the first experimental results for microwave spectroscopy of the
hyperfine structure of antiprotonic He-3. Due to the helium nuclear spin,
antiprotonic He-3 has a more complex hyperfine structure than antiprotonic He-4
which has already been studied before. Thus a comparison between theoretical
calculations and the experimental results will provide a more stringent test of
the three-body quantum electrodynamics (QED) theory. Two out of four
super-super-hyperfine (SSHF) transition lines of the (n,L)=(36,34) state were
observed. The measured frequencies of the individual transitions are
11.12559(14) GHz and 11.15839(18) GHz, less than 1 MHz higher than the current
theoretical values, but still within their estimated errors. Although the
experimental uncertainty for the difference of these frequencies is still very
large as compared to that of theory, its measured value agrees with theoretical
calculations. This difference is crucial to be determined because it is
proportional to the magnetic moment of the antiproton.Comment: 8 pages, 6 figures, just published (online so far) in Physics Letters
Orientifolds of Gepner Models
We systematically construct and study Type II Orientifolds based on Gepner
models which have N=1 supersymmetry in 3+1 dimensions. We classify the parity
symmetries and construct the crosscap states. We write down the conditions that
a configuration of rational branes must satisfy for consistency (tadpole
cancellation and rank constraints) and spacetime supersymmetry. For certain
cases, including Type IIB orientifolds of the quintic and a two parameter
model, one can find all solutions in this class. Depending on the parity, the
number of vacua can be large, of the order of 10^{10}-10^{13}. For other
models, it is hard to find all solutions but special solutions can be found --
some of them are chiral. We also make comparison with the large volume regime
and obtain a perfect match. Through this study, we find a number of new
features of Type II orientifolds, including the structure of moduli space and
the change in the type of O-planes under navigation through non-geometric
phases.Comment: 142 page
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