18,934 research outputs found
Decentralized formation control with connectivity maintenance and collision avoidance under limited and intermittent sensing
A decentralized switched controller is developed for dynamic agents to
perform global formation configuration convergence while maintaining network
connectivity and avoiding collision within agents and between stationary
obstacles, using only local feedback under limited and intermittent sensing.
Due to the intermittent sensing, constant position feedback may not be
available for agents all the time. Intermittent sensing can also lead to a
disconnected network or collisions between agents. Using a navigation function
framework, a decentralized switched controller is developed to navigate the
agents to the desired positions while ensuring network maintenance and
collision avoidance.Comment: 8 pages, 2 figures, submitted to ACC 201
The Economics of Mortgage Terminations: Implications for Mortgage Lenders and Mortgage Terms
The paper begins with the development of models explaining the mortgage refinancing and assumption decisions of households Having identified the economic variables influencing these decisions, we then simulate the models for different values to determine under what conditions households will refinance or assume. Finally, we draw some implications of these results for: (1) the impact of a decline in mortgage rates on the asset portfolio yields of mortgage lending institutions and (2) the effect of the observed rise in interest rate volatility, including the optimal terminations response of mortgage borrowers, on the terms of the mortgage contract and the returns to mortgage lenders on recently issued mortgage loans.
Stationary Cycling Induced by Switched Functional Electrical Stimulation Control
Functional electrical stimulation (FES) is used to activate the dysfunctional
lower limb muscles of individuals with neuromuscular disorders to produce
cycling as a means of exercise and rehabilitation. However, FES-cycling is
still metabolically inefficient and yields low power output at the cycle crank
compared to able-bodied cycling. Previous literature suggests that these
problems are symptomatic of poor muscle control and non-physiological muscle
fiber recruitment. The latter is a known problem with FES in general, and the
former motivates investigation of better control methods for FES-cycling.In
this paper, a stimulation pattern for quadriceps femoris-only FES-cycling is
derived based on the effectiveness of knee joint torque in producing forward
pedaling. In addition, a switched sliding-mode controller is designed for the
uncertain, nonlinear cycle-rider system with autonomous state-dependent
switching. The switched controller yields ultimately bounded tracking of a
desired trajectory in the presence of an unknown, time-varying, bounded
disturbance, provided a reverse dwell-time condition is satisfied by
appropriate choice of the control gains and a sufficient desired cadence.
Stability is derived through Lyapunov methods for switched systems, and
experimental results demonstrate the performance of the switched control system
under typical cycling conditions.Comment: 8 pages, 3 figures, submitted to ACC 201
Homologous self-organising scale-invariant properties characterise long range species spread and cancer invasion
The invariance of some system properties over a range of temporal and/or spatial scales is an attribute of many processes in nature1, often characterised by power law functions and fractal geometry2. In particular, there is growing consensus in that fat-tailed functions like the power law adequately describe long-distance dispersal (LDD) spread of organisms 3,4. Here we show that the spatial spread of individuals governed by a power law dispersal function is represented by a clear and unique signature, characterised by two properties: A fractal geometry of the boundaries of patches generated by dispersal with a fractal dimension D displaying universal features, and a disrupted patch size distribution characterised by two different power laws. Analysing patterns obtained by simulations and real patterns from species dispersal and cell spread in cancer invasion we show that both pattern properties are a direct result of LDD and localised dispersal and recruitment, reflecting population self-organisation
SO(5) Superconductors in a Zeeman Magnetic Field
The generic symmetry of a system under a uniform Zeeman magnetic field is
U(1) x U(1). However, we show that SO(5) models in the presence of a finite
chemical potential and a finite Zeeman magnetic field can have a exact SU(2) x
U(1) symmetry. This principle can be used to test SO(5) symmetry at any doping
level
Vortex configurations of bosons in an optical lattice
The single vortex problem in a strongly correlated bosonic system is
investigated self-consistently within the mean-field theory of the Bose-Hubbard
model. Near the superfluid-Mott transition, the vortex core has a tendency
toward the Mott-insulating phase, with the core particle density approaching
the nearest commensurate value. If the nearest neighbor repulsion exists, the
charge density wave order may develop locally in the core. The evolution of the
vortex configuration from the strong to weak coupling regions is studied. This
phenomenon can be observed in systems of rotating ultra-cold atoms in optical
lattices and Josephson junction arraysComment: 4 pages, 4 figs, Accepted by Physics Review
Order picking optimization with order assignment and multiple workstations in KIVA warehouses
We consider the problem of allocating orders and racks to multiple stations
and sequencing their interlinked processing flows at each station in the
robot-assisted KIVA warehouse. The various decisions involved in the problem,
which are closely associated and must be solved in real time, are often tackled
separately for ease of treatment. However, exploiting the synergy between order
assignment and picking station scheduling benefits picking efficiency. We
develop a comprehensive mathematical model that takes the synergy into
consideration to minimize the total number of rack visits. To solve this
intractable problem, we develop an efficient algorithm based on simulated
annealing and dynamic programming. Computational studies show that the proposed
approach outperforms the rule-based policies used in practice in terms of
solution quality. Moreover, the results reveal that ignoring the order
assignment policy leads to considerable optimality gaps for real-world-sized
instances
Dissociation energy of the hydrogen molecule at 10 accuracy
The ionization energy of ortho-H has been determined to be
cm
from measurements of the GK(1,1)--X(0,1) interval by Doppler-free two-photon
spectroscopy using a narrow band 179-nm laser source and the ionization energy
of the GK(1,1) state by continuous-wave near-infrared laser spectroscopy.
(H) was used to derive the dissociation energy of
H, (H), at cm with a
precision that is more than one order of magnitude better than all previous
results. The new result challenges calculations of this quantity and represents
a benchmark value for future relativistic and QED calculations of molecular
energies.Comment: 6 pages, 5 figure
Otopetrin 1 protects mice from obesity-associated metabolic dysfunction through attenuating adipose tissue inflammation.
Chronic low-grade inflammation is emerging as a pathogenic link between obesity and metabolic disease. Persistent immune activation in white adipose tissue (WAT) impairs insulin sensitivity and systemic metabolism, in part, through the actions of proinflammatory cytokines. Whether obesity engages an adaptive mechanism to counteract chronic inflammation in adipose tissues has not been elucidated. Here we identified otopetrin 1 (Otop1) as a component of a counterinflammatory pathway that is induced in WAT during obesity. Otop1 expression is markedly increased in obese mouse WAT and is stimulated by tumor necrosis factor-α in cultured adipocytes. Otop1 mutant mice respond to high-fat diet with pronounced insulin resistance and hepatic steatosis, accompanied by augmented adipose tissue inflammation. Otop1 attenuates interferon-γ (IFN-γ) signaling in adipocytes through selective downregulation of the transcription factor STAT1. Using a tagged vector, we found that Otop1 physically interacts with endogenous STAT1. Thus, Otop1 defines a unique target of cytokine signaling that attenuates obesity-induced adipose tissue inflammation and plays an adaptive role in maintaining metabolic homeostasis in obesity
Quantifying the toroidal flux of preexisting flux ropes of coronal mass ejections
Funding: SOHO is a project of international cooperation between ESA and NASA. C.X., X.C. and M.D.D. are funded by NSFC grants 11722325, 11733003, 11790303, 11790300, Jiangsu NSF grants BK20170011, and "Dengfeng B" program of Nanjing University.In past decades, much progress has been achieved in understanding the origin and evolution of coronal mass ejections (CMEs). In situ observations of the counterparts of CMEs, especially magnetic clouds (MCs) near the Earth, have provided measurements of the structure and total flux of CME flux ropes. However, it has been difficult to measure these properties in an erupting CME flux rope, in particular in a preexisting flux rope. In this work, we propose a model to estimate the toroidal flux of a preexisting flux rope by subtracting the flux contributed by magnetic reconnection during the eruption from the flux measured in the MC. The flux contributed by the reconnection is derived from geometric properties of two-ribbon flares based on a quasi-2D reconnection model. We then apply the model to four CME/flare events and find that the ratio of toroidal flux in the preexisting flux rope to that in the associated MC lies in the range 0.40–0.88. This indicates that the toroidal flux of the preexisting flux rope makes an important contribution to that of the CME flux rope and is usually at least as large as the flux arising from the eruption process for the selected events.Publisher PDFPeer reviewe
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