4,901 research outputs found
The low noise phase of a 2d active nematic
We consider a collection of self-driven apolar particles on a substrate that
organize into an active nematic phase at sufficiently high density or low
noise. Using the dynamical renormalization group, we systematically study the
2d fluctuating ordered phase in a coarse-grained hydrodynamic description
involving both the nematic director and the conserved density field. In the
presence of noise, we show that the system always displays only quasi-long
ranged orientational order beyond a crossover scale. A careful analysis of the
nonlinearities permitted by symmetry reveals that activity is dangerously
irrelevant over the linearized description, allowing giant number fluctuations
to persist though now with strong finite-size effects and a non-universal
scaling exponent. Nonlinear effects from the active currents lead to power law
correlations in the density field thereby preventing macroscopic phase
separation in the thermodynamic limit.Comment: 17 pages, 5 figure
THE SCOPE OF CISG IN CHINA AND BRAZIL AND FACILITATION OF TRADE WITH PORTUGUESE SPEAKING COUNTRIES
Trade facilitation achieved through harmonization of private law governing international trade is well recognized. The CISG, albeit being a hall mark of a successful harmonization attracted a limited interest from the Portuguese speaking (Lusophone) countries except Brazil. In the light of China’s trading interest with the Lusophone Countries, the question of relevance of the CISG to promote Sino-Lusophone trade gains significance. To address the above question, this paper seeks to examine the scope and limitations of the CISG application to China and Brazil and adopts a case law method to examine the jurisprudence resulting from judicial interpretations and arbitration awards. The paper examines the reception of the CISG in both countries, before enquiring the significance of the CISG in facilitating their bilateral trade. The paper briefly refers to the implications arising from the lack of formal extension of the CISG by China to Macau SAR, which has been designated as a jurisdiction to facilitate trade between China and Lusophone Countries. In conclusion, the paper underscores the importance of the CISG based on the findings of its scope of application in China and Brazil and calls for the need to study the phenomenon further in the light of the experience of post Brazilian accession to the CISG. 
Defect unbinding in active nematics
We formulate the statistical dynamics of topological defects in the active
nematic phase, formed in two dimensions by a collection of self-driven
particles on a substrate. An important consequence of the non-equilibrium drive
is the spontaneous motility of strength +1/2 disclinations. Starting from the
hydrodynamic equations of active nematics, we derive an interacting particle
description of defects that includes active torques. We show that activity,
within perturbation theory, lowers the defect-unbinding transition temperature,
determining a critical line in the temperature-activity plane that separates
the quasi-long-range ordered (nematic) and disordered (isotropic) phases. Below
a critical activity, defects remain bound as rotational noise decorrelates the
directed dynamics of +1/2 defects, stabilizing the quasi-long-range ordered
nematic state. This activity threshold vanishes at low temperature, leading to
a re-entrant transition. At large enough activity, active forces always exceed
thermal ones and the perturbative result fails, suggesting that in this regime
activity will always disorder the system. Crucially, rotational diffusion being
a two-dimensional phenomenon, defect unbinding cannot be described by a
simplified one-dimensional model.Comment: 15 pages (including SI), 4 figures. Significant technical
improvements without changing the result
Do current-density nonlinearities cut off the glass transition?
Extended mode coupling theories for dense fluids predict that nonlinear
current-density couplings cut off the singular `ideal glass transition',
present in the standard mode coupling theory where such couplings are ignored.
We suggest here that, rather than allowing for activated processes as sometimes
supposed, contributions from current-density couplings are always negligible
close to a glass transition. We discuss in schematic terms how activated
processes can nonetheless cut off the transition, by causing the memory
function to become linear in correlators at late times.Comment: 4 page
An efficient reconfigurable geographic routing congestion control algorithm for wireless sensor networks
In recent times, huge data is transferred from source to destination through multi path in wireless sensor networks (WSNs). Due to this more congestion occurs in the communication path. Hence, original data will be lost and delay problems arise at receiver end. The above-mentioned drawbacks can be overcome by the proposed efficient reconfigurable geographic routing congestion control (RgRCC) algorithm for wireless sensor networks. the proposed algorithm efficiently finds the node’s congestion status with the help queue length’s threshold level along with its change rate. Apart from this, the proposed algorithm re-routes the communication path to avoid congestion and enhances the strength of scalability of data communication in WSNs. The proposed algorithm frequently updates the distance between the nodes and by-pass routing holes, common for geographical routing. when the nodes are at the edge of the hole, it will create congestion between the nodes in WSNs. Apart from this, more nodes sink due to congestion. it can be reduced with the help of the proposed RgRCC algorithm. As per the simulation analysis, the proposed work indicates improved performance in comparison to conventional algorithm. By effectively identifying the data congestion in WSNs with high scalability rate as compared to conventional method
Local module identification in dynamic networks with correlated noise: the full input case
The identification of local modules in dynamic networks with known topology
has recently been addressed by formulating conditions for arriving at
consistent estimates of the module dynamics, typically under the assumption of
having disturbances that are uncorrelated over the different nodes. The
conditions typically reflect the selection of a set of node signals that are
taken as predictor inputs in a MISO identification setup. In this paper an
extension is made to arrive at an identification setup for the situation that
process noises on the different node signals can be correlated with each other.
In this situation the local module may need to be embedded in a MIMO
identification setup for arriving at a consistent estimate with maximum
likelihood properties. This requires the proper treatment of confounding
variables. The result is an algorithm that, based on the given network topology
and disturbance correlation structure, selects an appropriate set of node
signals as predictor inputs and outputs in a MISO or MIMO identification setup.
As a first step in the analysis, we restrict attention to the (slightly
conservative) situation where the selected output node signals are predicted
based on all of their in-neighbor node signals in the network.Comment: Extended version of paper submitted to the 58th IEEE Conf. Decision
and Control, Nice, 201
- …