2,915 research outputs found
A simple spreadsheet model to incorporate seasonal growth into length-based stock assessment methods
The paper describes a method by which seasonal growth can be incorporated into length-converted catch curves and cohort analyses using a spreadsheet. The method is based on calculating the length of fish using seasonal growth parameters on a daily basis. A LOOKUP function is then used to find the age corresponding to the length
Electronic Transport Spectroscopy of Carbon Nanotubes in a Magnetic Field
We report magnetic field spectroscopy measurements in carbon nanotube quantum
dots exhibiting four-fold shell structure in the energy level spectrum. The
magnetic field induces a large splitting between the two orbital states of each
shell, demonstrating their opposite magnetic moment and determining transitions
in the spin and orbital configuration of the quantum dot ground state. We use
inelastic cotunneling spectroscopy to accurately resolve the spin and orbital
contributions to the magnetic moment. A small coupling is found between
orbitals with opposite magnetic moment leading to anticrossing behavior at zero
field.Comment: 7 pages, 4 figure
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Hubbard ladders in a magnetic field
The behavior of a two leg Hubbard ladder in the presence of a magnetic field is studied by means of Abelian bosonization. We predict the appearance of a new (doping dependent) plateau in the magnetization curve of a doped 2-leg spin ladder in a wide range of couplings. We also discuss the extension to N-leg Hubbard ladders
Numerical Optimization of Underactuated Flexure-Based Grippers
Robotic manipulation in the agri-food industry faces several issues, including object variation, fragility and food safety. Underactuated flexure-based gripper allow passive adaptation to object variation, whilst monolithic flexure joints drive down cost, part-count, hygiene requirements, contamination and wear. However, designing flexure-based grippers presents challenges in achieving sufficient support stiffness, load-bearing capacity and joint deflection. Additionally, modeling the non-linear flexure behavior may become computationally expensive, especially under wide a variety of load cases, limiting the optimization approaches to simple structures and joints. In this work we present an interleaved computational optimization algorithm for underactuated flexure-based grippers, aimed at maximizing the range of graspable circular objects under a given load. This method achieves a superior design faster than state-of-the-art methods that optimize all design parameters simultaneously. A prototype constructed using rapid-prototyping validates the usage of the design method, and experimentally illustrates gripper performance
Dimensional crossover of a boson gas in multilayers
We obtain the thermodynamic properties for a non-interacting Bose gas
constrained on multilayers modeled by a periodic Kronig-Penney delta potential
in one direction and allowed to be free in the other two directions. We report
Bose-Einstein condensation (BEC) critical temperatures, chemical potential,
internal energy, specific heat, and entropy for different values of a
dimensionless impenetrability between layers. The BEC critical
temperature coincides with the ideal gas BEC critical temperature
when and rapidly goes to zero as increases to infinity for
any finite interlayer separation. The specific heat \textit{vs} for
finite and plane separation exhibits one minimum and one or two maxima
in addition to the BEC, for temperatures larger than which highlights
the effects due to particle confinement. Then we discuss a distinctive
dimensional crossover of the system through the specific heat behavior driven
by the magnitude of . For the crossover is revealed by the change
in the slope of and when , it is evidenced by a broad
minimum in .Comment: Ten pages, nine figure
Universal scaling of flow curves: comparison between experiments and simulations
Yield stress materials form an interesting class of materials that behave
like solids at small stresses, but start to flow once a critical stress is
exceeded. It has already been reported both in experimental and simulation work
that flow curves of different yield stress materials can be scaled with the
distance to jamming or with the confining pressure. However, different scaling
exponents are found between experiments and simulations. In this paper we
identify sources of this discrepancy. We numerically relate the volume fraction
with the confining pressure and discuss the similarities and differences
between rotational and oscillatory measurements. Whereas simulations are
performed in the elastic response regime close to the jamming transition and
with very small amplitudes to calculate the scaling exponents, these conditions
are hardly possible to achieve experimentally. Measurements are often performed
far away from the critical volume fraction and at large amplitudes. We show
that these differences are the underlying reason for the different exponents
for rescaling flow curves
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