7,463 research outputs found
Mechanical Characterization of Torsional Micropaddles Using Atomic Force Microscopy
The reference cantilever method is shown to act as a direct and simple method for determination of torsional spring constant. It has been applied to the characterization of micropaddle structures similar to those proposed for resonant functionalized chemical sensors and resonant thermal detectors. It is shown that this method can be used as an effective procedure to characterize a key parameter of these devices and would be applicable to characterization of other similar MEMS/NEMS devices such as micromirrors. In this study, two sets of micropaddles are manufactured (beams at centre and offset by 2.5 μm) by using LPCVD silicon nitride as a substrate. The patterning is made by direct milling using focused ion beam. The torsional spring constant is achieved through micromechanical analysis via atomic force microscopy. To obtain the gradient of force curve, the area of the micropaddle is scanned and the behaviour of each pixel is investigated through an automated developed code. The experimental results are in a good agreement with theoretical results
Transition from small to large world in growing networks
We examine the global organization of growing networks in which a new vertex
is attached to already existing ones with a probability depending on their age.
We find that the network is infinite- or finite-dimensional depending on
whether the attachment probability decays slower or faster than .
The network becomes one-dimensional when the attachment probability decays
faster than . We describe structural characteristics of these
phases and transitions between them.Comment: 5 page
Compact parity conserving percolation in one-dimension
Compact directed percolation is known to appear at the endpoint of the
directed percolation critical line of the Domany-Kinzel cellular automaton in
1+1 dimension. Equivalently, such transition occurs at zero temperature in a
magnetic field H, upon changing the sign of H, in the one-dimensional
Glauber-Ising model with well known exponents characterising spin-cluster
growth. We have investigated here numerically these exponents in the
non-equilibrium generalization (NEKIM) of the Glauber model in the vicinity of
the parity-conserving phase transition point of the kinks. Critical
fluctuations on the level of kinks are found to affect drastically the
characteristic exponents of spreading of spins while the hyperscaling relation
holds in its form appropriate for compact clusters.Comment: 7 pages, 7 figures embedded in the latex, final form before J.Phys.A
publicatio
Laplacian spectra of complex networks and random walks on them: Are scale-free architectures really important?
We study the Laplacian operator of an uncorrelated random network and, as an
application, consider hopping processes (diffusion, random walks, signal
propagation, etc.) on networks. We develop a strict approach to these problems.
We derive an exact closed set of integral equations, which provide the averages
of the Laplacian operator's resolvent. This enables us to describe the
propagation of a signal and random walks on the network. We show that the
determining parameter in this problem is the minimum degree of vertices
in the network and that the high-degree part of the degree distribution is not
that essential. The position of the lower edge of the Laplacian spectrum
appears to be the same as in the regular Bethe lattice with the
coordination number . Namely, if , and
if . In both these cases the density of eigenvalues
as , but the limiting behaviors near
are very different. In terms of a distance from a starting vertex,
the hopping propagator is a steady moving Gaussian, broadening with time. This
picture qualitatively coincides with that for a regular Bethe lattice. Our
analytical results include the spectral density near
and the long-time asymptotics of the autocorrelator and the
propagator.Comment: 25 pages, 4 figure
Organization of complex networks without multiple connections
We find a new structural feature of equilibrium complex random networks
without multiple and self-connections. We show that if the number of
connections is sufficiently high, these networks contain a core of highly
interconnected vertices. The number of vertices in this core varies in the
range between and , where is the number of
vertices in a network. At the birth point of the core, we obtain the
size-dependent cut-off of the distribution of the number of connections and
find that its position differs from earlier estimates.Comment: 5 pages, 2 figure
Adubação nitrogenada no cultivo do feijoeiro comum irrigado sob plantio direto.
Este trabalho tem por objetivo apresentar os principais resultados de pesquisa sobre adubação nitrogenada de cobertura para o feijoeiro irrigado, realizada na região Noroeste de Minas Gerais, e discutir, à luz dos conhecimentos atuais, alguns conceitos de adubação nitrogenada visando ao desenvolvimento de sistemas agrícolas que sejam econômicos e com sustentabilidade ambiental.bitstream/CNPAF/23536/1/circ_70.pd
Utilização do medidor do teor de clorofila para recomendação da adubação nitrogenada de cobertura do feijoeiro irrigado.
O objetivo deste estudo foi encontrar uma alternativa ao método convencional de adubação de cobertura que indique a necessidade de suplementação de N na época de maior demanda da cultura do feijoeiro irrigado, mediante o uso do clorofilômetro.bitstream/CNPAF/26602/1/comt_142.pd
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