Optimal read/write memory system components

Two holographic data storage and display systems, voltage gradient ionization system, and linear strain manipulation system are discussed in terms of creating fast, high bit density, storage device. Components described include: novel mounting fixture for photoplastic arrays; corona discharge device; and block data composer

Modeling of SAR signatures of shallow water ocean topography

A hydrodynamic/electromagnetic model was developed to explain and quantify the relationship between the SEASAT synthetic aperture radar (SAR) observed signatures and the bottom topography of the ocean in the English Channel region of the North Sea. The model uses environmental data and radar system parameters as inputs and predicts SAR-observed backscatter changes over topographic changes in the ocean floor. The model results compare favorably with the actual SEASAT SAR observed backscatter values. The developed model is valid for only relatively shallow water areas (i.e., less than 50 meters in depth) and suggests that for bottom features to be visible on SAR imagery, a moderate to high velocity current and a moderate wind must be present

Optical read/write memory system components

The optical components of a breadboard holographic read/write memory system have been fabricated and the parameters specified of the major system components: (1) a laser system; (2) an x-y beam deflector; (3) a block data composer; (4) the read/write memory material; (5) an output detector array; and (6) the electronics to drive, synchronize, and control all system components. The objectives of the investigation were divided into three concurrent phases: (1) to supply and fabricate the major components according to the previously established specifications; (2) to prepare computer programs to simulate the entire holographic memory system so that a designer can balance the requirements on the various components; and (3) to conduct a development program to optimize the combined recording and reconstruction process of the high density holographic memory system

Monte-Carlo methods for NLTE spectral synthesis of supernovae

We present JEKYLL, a new code for modelling of supernova (SN) spectra and lightcurves based on Monte-Carlo (MC) techniques for the radiative transfer. The code assumes spherical symmetry, homologous expansion and steady state for the matter, but is otherwise capable of solving the time-dependent radiative transfer problem in non-local-thermodynamic-equilibrium (NLTE). The method used was introduced in a series of papers by Lucy, but the full time-dependent NLTE capabilities of it have never been tested. Here, we have extended the method to include non-thermal excitation and ionization as well as charge-transfer and two-photon processes. Based on earlier work, the non-thermal rates are calculated by solving the Spencer-Fano equation. Using a method previously developed for the SUMO code, macroscopic mixing of the material is taken into account in a statistical sense. In addition, a statistical Markov-chain model is used to sample the emission frequency, and we introduce a method to control the sampling of the radiation field. Except for a description of JEKYLL, we provide comparisons with the ARTIS, SUMO and CMFGEN codes, which show good agreement in the calculated spectra as well as the state of the gas. In particular, the comparison with CMFGEN, which is similar in terms of physics but uses a different technique, shows that the Lucy method does indeed converge in the time-dependent NLTE case. Finally, as an example of the time-dependent NLTE capabilities of JEKYLL, we present a model of a Type IIb SN, taken from a set of models presented and discussed in detail in an accompanying paper. Based on this model we investigate the effects of NLTE, in particular those arising from non-thermal excitation and ionization, and find strong effects even on the bolometric lightcurve. This highlights the need for full NLTE calculations when simulating the spectra and lightcurves of SNe.Comment: Accepted for publication by Astronomy & Astrophysic

Асимптотическое поведение одного класса решений нелинейных неавтономных дифференциальных уравнений второго порядка

For the ordinary differential second-kind equation containing in a right member the sum composed with correctly varying concerning unknown function and its derivative of the first order by nonlinearities, necessary and sufficient existence enough a wide class of monotone solutions, and as exact asymptotic representations of solutions from the given class in a neighborhood of a singular point are established

Асимптотичні зображення роз'язків диференціальних рівнянь другого порядку з правильно мінливими відносно невідомої функції та її похідної першого порядку нелінійностями

автореферат дисертаці

Условия существования и асимптотика одного класса решений существенно нелинейных дифференциальных уравнений второго порядка

We consider the ordinary differential equation of the second order containing in the righthand side the sum of nonlinearities correctly varying concerning unknown function and its derivative of the first order. Necessary and sufficient conditions of existence of a wide class of monotone solutions, and exact asymptotic representations of solutions from the given class in a neighborhood of a singular point are established.Для обыкновенного дифференциального уравнения второго порядка, содержащего в правой части сумму слагаемых с правильно меняющимися относительно неизвестной фун- кции и её производной первого порядка нелинейностями, установлены необходимые и до- статочные условия существования широкого класса монотонных решений, а также точные асимптотические представления для решений из данного класса в окрестности особой точки

Consensus formation on coevolving networks: groups' formation and structure

We study the effect of adaptivity on a social model of opinion dynamics and consensus formation. We analyze how the adaptivity of the network of contacts between agents to the underlying social dynamics affects the size and topological properties of groups and the convergence time to the stable final state. We find that, while on static networks these properties are determined by percolation phenomena, on adaptive networks the rewiring process leads to different behaviors: Adaptive rewiring fosters group formation by enhancing communication between agents of similar opinion, though it also makes possible the division of clusters. We show how the convergence time is determined by the characteristic time of link rearrangement. We finally investigate how the adaptivity yields nontrivial correlations between the internal topology and the size of the groups of agreeing agents.Comment: 10 pages, 3 figures,to appear in a special proceedings issue of J. Phys. A covering the "Complex Networks: from Biology to Information Technology" conference (Pula, Italy, 2007

Evolution equation for a model of surface relaxation in complex networks

In this paper we derive analytically the evolution equation of the interface for a model of surface growth with relaxation to the minimum (SRM) in complex networks. We were inspired by the disagreement between the scaling results of the steady state of the fluctuations between the discrete SRM model and the Edward-Wilkinson process found in scale-free networks with degree distribution $P(k) \sim k^{-\lambda}$ for $\lambda <3$ [Pastore y Piontti {\it et al.}, Phys. Rev. E {\bf 76}, 046117 (2007)]. Even though for Euclidean lattices the evolution equation is linear, we find that in complex heterogeneous networks non-linear terms appear due to the heterogeneity and the lack of symmetry of the network; they produce a logarithmic divergency of the saturation roughness with the system size as found by Pastore y Piontti {\it et al.} for $\lambda <3$.Comment: 9 pages, 2 figure

Асимптотические представления решений дифференциальных уравнений второго порядка с правильно меняющимися относительно неизвестной функции и ее производной первого порядка нелинейностями

диссертацияРабота носит теоретический характер. Результаты диссертации и разработанные в ней методы исследования могут быть использованы при изучении асимптотических свойств решений дифференциальных уравнений более высоких порядков с правильно меняющимися нелинейностями. Кроме того, данные результаты могут быть применены для рассмотрения конкретных нелинейных дифференциальных уравнений второго порядка, возникающих в различных областях естествознания