Justification of binder material selection for carbon particles incorporation into fibrous electromagnetic radiation absorber

The paper presents justification of a binder material for incorporating carbon particles into the interfiber space of electromagnetic radiation absorber. A method for carbon particles incorporation into a fibrous material has been developed. It is based on applying a carbon-containing nanocomposite to the fibrous material’s surface. Previously, the research of carbon particles incorporation into a synthetic material by using an aqueous solution were carried out, which ensured a uniform distribution of carbon particles in the material structure. However, the properties of the material have changed significantly upon mechanical deformation. Therefore, the carbon particles incorporation process was investigated using various nanocomposites obtained on the basis of mixtures of vinyl acetate polymer, or epoxy polymer, or surface-active substance with carbon black. Based on the results of electron microscopic analysis and the reflection and transmission coefficients frequency dependences in the frequency range 0.7–17 GHz, the efficiency of using a nanocomposite based on a mixture of surface-active substance and carbon black to create electromagnetic radiation absorbers was justified. Such electromagnetic radiation absorbers have the transmission coefficient value about –18 dB and reflection coefficient value about –12 dB in the frequency range 7–13 GHz. Carbon-containing electromagnetic radiation absorbers based on fibrous material have thickness less than 3 mm, properties of flexibility and resistance to mechanical deformation. It can be used in various fields, in particular for hiding objects from radio frequency reconnaissance or protecting equipment from external interference.The paper presents justification of a binder material for incorporating carbon particles into the interfiber space of electromagnetic radiation absorber. A method for carbon particles incorporation into a fibrous material has been developed. It is based on applying a carbon-containing nanocomposite to the fibrous material’s surface. Previously, the research of carbon particles incorporation into a synthetic material by using an aqueous solution were carried out, which ensured a uniform distribution of carbon particles in the material structure. However, the properties of the material have changed significantly upon mechanical deformation. Therefore, the carbon particles incorporation process was investigated using various nanocomposites obtained on the basis of mixtures of vinyl acetate polymer, or epoxy polymer, or surface-active substance with carbon black. Based on the results of electron microscopic analysis and the reflection and transmission coefficients frequency dependences in the frequency range 0.7–17 GHz, the efficiency of using a nanocomposite based on a mixture of surface-active substance and carbon black to create electromagnetic radiation absorbers was justified. Such electromagnetic radiation absorbers have the transmission coefficient value about –18 dB and reflection coefficient value about –12 dB in the frequency range 7–13 GHz. Carbon-containing electromagnetic radiation absorbers based on fibrous material have thickness less than 3 mm, properties of flexibility and resistance to mechanical deformation. It can be used in various fields, in particular for hiding objects from radio frequency reconnaissance or protecting equipment from external interference

Possible Quantum Spin Liquid States on the Triangular and Kagome Lattices

The frustrated spin-one-half Heisenberg model on triangualr and Kagome Lattices is mapped onto a single specis of fermion carrying statistical flux. The corresponding Chern-Simons gauge theory is analyzed at the Gaussian level and found to be massive. This provides a new motivation for the spin-liquid Kalmeyer-Laughlin wave function. Good overlap of this wave function with the numerical ground state is found for small clusters.Comment: 13 pages, revtex. IUCM-920

Comparison of Fermi-LAT and CTA in the region between 10-100 GeV

The past decade has seen a dramatic improvement in the quality of data available at both high (HE: 100 MeV to 100 GeV) and very high (VHE: 100 GeV to 100 TeV) gamma-ray energies. With three years of data from the Fermi Large Area Telescope (LAT) and deep pointed observations with arrays of Cherenkov telescope, continuous spectral coverage from 100 MeV to $\sim10$ TeV exists for the first time for the brightest gamma-ray sources. The Fermi-LAT is likely to continue for several years, resulting in significant improvements in high energy sensitivity. On the same timescale, the Cherenkov Telescope Array (CTA) will be constructed providing unprecedented VHE capabilities. The optimisation of CTA must take into account competition and complementarity with Fermi, in particularly in the overlapping energy range 10$-$100 GeV. Here we compare the performance of Fermi-LAT and the current baseline CTA design for steady and transient, point-like and extended sources.Comment: Accepted for Publication in Astroparticle Physic

Predicting Intermediate Storage Performance for Workflow Applications

Configuring a storage system to better serve an application is a challenging task complicated by a multidimensional, discrete configuration space and the high cost of space exploration (e.g., by running the application with different storage configurations). To enable selecting the best configuration in a reasonable time, we design an end-to-end performance prediction mechanism that estimates the turn-around time of an application using storage system under a given configuration. This approach focuses on a generic object-based storage system design, supports exploring the impact of optimizations targeting workflow applications (e.g., various data placement schemes) in addition to other, more traditional, configuration knobs (e.g., stripe size or replication level), and models the system operation at data-chunk and control message level. This paper presents our experience to date with designing and using this prediction mechanism. We evaluate this mechanism using micro- as well as synthetic benchmarks mimicking real workflow applications, and a real application.. A preliminary evaluation shows that we are on a good track to meet our objectives: it can scale to model a workflow application run on an entire cluster while offering an over 200x speedup factor (normalized by resource) compared to running the actual application, and can achieve, in the limited number of scenarios we study, a prediction accuracy that enables identifying the best storage system configuration

Quadrupole collective modes in trapped finite-temperature Bose-Einstein condensates

Finite temperature simulations are used to study quadrupole excitations of a trapped Bose-Einstein condensate. We focus specifically on the m=0 mode, where a long-standing theoretical problem has been to account for an anomalous variation of the mode frequency with temperature. We explain this behavior in terms of the excitation of two separate modes, corresponding to coupled motion of the condensate and thermal cloud. The relative amplitudes of the modes depends sensitively on the temperature and on the frequency of the harmonic drive used to excite them. Good agreement with experiment is found for appropriate drive frequencies.Comment: 4 pages, 3 figure

Role of the potential landscape on the single-file diffusion through channels.

Transport of colloid particles through narrow channels is ubiquitous in cell biology as well as becoming increasingly important for microfluidic applications or targeted drug delivery. Membrane channels in cells are useful models for artificial designs because of their high efficiency, selectivity, and robustness to external fluctuations. Here, we model the passive channels that let cargo simply diffuse through them, affected by a potential profile along the way. Passive transporters achieve high levels of efficiency and specificity from binding interactions with the cargo inside the channel. This however leads to a paradox: why should channels which are so narrow that they are blocked by their cargo evolve to have binding regions for their cargo if that will effectively block them? Using Brownian dynamics simulations, we show that different potentials, notably symmetric, increase the flux through narrow passive channels - and investigate how shape and depth of potentials influence the flux. We find that there exist optimal depths for certain potential shapes and that it is most efficient to apply a small force over an extended region of the channel. On the other hand, having several spatially discrete binding pockets will not alter the flux significantly. We also explore the role of many-particle effects arising from pairwise particle interactions with their neighbours and demonstrate that the relative changes in flux can be accounted for by the kinetics of the absorption reaction at the end of the channel.Simulations were funded by the Cavendish Laboratory teaching committee and per- formed using the Darwin Supercomputer of the Univer- sity of Cambridge High Performance Computing Service (http://www.hpc.cam.ac.uk/), provided by Dell Inc. us- ing Strategic Research Infrastructure Funding from the Higher Education Funding Council for England.This is the accepted manuscript. The final version is available from AIP at http://scitation.aip.org/content/aip/journal/jcp/141/22/10.1063/1.490317

A remark on the three approaches to 2D Quantum gravity

The one-matrix model is considered. The generating function of the correlation numbers is defined in such a way that this function coincide with the generating function of the Liouville gravity. Using the Kontsevich theorem we explain that this generating function is an analytic continuation of the generating function of the Topological gravity. We check the topological recursion relations for the correlation functions in the $p$-critical Matrix model.Comment: 11 pages. Title changed, presentation improve

Swift J164449.3+573451 event: generation in the collapsing star cluster?

We discuss the multiband energy release in a model of a collapsing galactic nucleus, and we try to interpret the unique super-long cosmic gamma-ray event Swift J164449.3+573451 (GRB 110328A by early classification) in this scenario. Neutron stars and stellar-mass black holes can form evolutionary a compact self-gravitating subsystem in the galactic center. Collisions and merges of these stellar remnants during an avalanche contraction and collapse of the cluster core can produce powerful events in different bands due to several mechanisms. Collisions of neutron stars and stellar-mass black holes can generate gamma-ray bursts (GRBs) similar to the ordinary models of short GRB origin. The bright peaks during the first two days may also be a consequence of multiple matter supply (due to matter release in the collisions) and accretion onto the forming supermassive black hole. Numerous smaller peaks and later quasi-steady radiation can arise from gravitational lensing, late accretion of gas onto the supermassive black hole, and from particle acceleration by shock waves. Even if this model will not reproduce exactly all the Swift J164449.3+573451 properties in future observations, such collapses of galactic nuclei can be available for detection in other events.Comment: 7 pages, replaced by the final versio