Learning multifractal structure in large networks

Generating random graphs to model networks has a rich history. In this paper, we analyze and improve upon the multifractal network generator (MFNG) introduced by Palla et al. We provide a new result on the probability of subgraphs existing in graphs generated with MFNG. From this result it follows that we can quickly compute moments of an important set of graph properties, such as the expected number of edges, stars, and cliques. Specifically, we show how to compute these moments in time complexity independent of the size of the graph and the number of recursive levels in the generative model. We leverage this theory to a new method of moments algorithm for fitting large networks to MFNG. Empirically, this new approach effectively simulates properties of several social and information networks. In terms of matching subgraph counts, our method outperforms similar algorithms used with the Stochastic Kronecker Graph model. Furthermore, we present a fast approximation algorithm to generate graph instances following the multi- fractal structure. The approximation scheme is an improvement over previous methods, which ran in time complexity quadratic in the number of vertices. Combined, our method of moments and fast sampling scheme provide the first scalable framework for effectively modeling large networks with MFNG

Behavior sensitivities for control augmented structures

During the past few years it has been recognized that combining passive structural design methods with active control techniques offers the prospect of being able to find substantially improved designs. These developments have stimulated interest in augmenting structural synthesis by adding active control system design variables to those usually considered in structural optimization. An essential step in extending the approximation concepts approach to control augmented structural synthesis is the development of a behavior sensitivity analysis capability for determining rates of change of dynamic response quantities with respect to changes in structural and control system design variables. Behavior sensitivity information is also useful for man-machine interactive design as well as in the context of system identification studies. Behavior sensitivity formulations for both steady state and transient response are presented and the quality of the resulting derivative information is evaluated

Influence of Visual Feedback On Dynamic Balance Control in Chronic Stroke Survivors

Chronic stroke survivors have an increased incidence of falls during walking, suggesting changes in dynamic balance control post-stroke. Despite this increased incidence of falls during walking, balance control is often studied only in standing. The purpose of this study was to quantify deficits in dynamic balance control during walking, and to evaluate the influence of visual feedback on this control in stroke survivors. Ten individuals with chronic stroke, and ten neurologically intact individuals participated in this study. Walking performance was assessed while participants walked on an instrumented split-belt treadmill with different types of visual feedback. Dynamic balance control was quantified using both the extent of center of mass (COM) movement in the frontal plane over a gait cycle (COM sway), and base of support (step width). Stroke survivors walked with larger COM sway and wider step widths compared to controls. Despite these baseline differences, both groups walked with a similar ratio of step width to COM sway (SW/COM). Providing a stationary target with a laser reference of body movement reduced COM sway only in the stroke group, indicating that visual feedback of sway alters dynamic balance control post-stroke. These results demonstrate that stroke survivors attempt to maintain a similar ratio of step width to COM movement, and visual cues can be used to help control COM movement during walking post-stroke

The Description and Interpretation of a Tertiary Siliceous Rock in Western North Dakota

In southeastern North Dakota, northwestern South Dakota and southeastern Montana, a previously poorly studied tertiary siliceous rock occurs in place, as residual boulders and as a gravel constituent. This rock is found associated with outcrops of all formations from the Cretaceous Hell Creek Formation to the Eocene Golden Valley Formation, though it can only be definitely attributed to the latter. It varies from an arenaceous chert to a sandy chert-cemented siltstone, the defining factor being the chert to detrital grain ratio. Macroscopically, it is typically dense, hard and dark gray in addition to containing numerous plant fossils. Exceptional occurrences are concretion-like. The detrital grains are generally moderately well sorted, subangular and silt-size. Some exhibit secondary overgrowths. Chert and plant matter, replaced and unreplaced, compose the rest of the rock. The siliceous rock seems to have been formed in a marsh or pond environment characterized by an extensive shallow basin with local depressions. Sediments deposited in these depressions were silicifed by the precipitation of ground water-transported silica. Precipitation of this silica, in the form of chert and secondary overgrowths, was facilitated by an acidic environment at the site of precipitation, a result of the introduction of CO2 and/or humic acids due to the decomposition of organic matter. Limited evidence suggests a multiple-horizon source for the siliceous rock

Manganese bismuth thin film for large capacity digital memories

Material and system research defines accurate memory characteristics in regard to write, read, erase and data operations of manganese bismuth materials

Influence of analysis and design models on minimum weight design

The results of numerical experiments designed to illustrate how the minimum weight design, accuracy, and cost can be influenced by: (1) refinement of the finite element analysis model and associated load path problems, and (2) refinement of the design variable linking model are examined. The numerical experiments range from simple structures where the modelling decisions are relatively obvious and less costly to the more complex structures where such decisions are less obvious and more costly. All numerical experiments used employ the dual formulation in ACCESS-3 computer program. Guidelines are suggested for creating analysis and design models that predict a minimum weight structure with greater accuracy and less cost. These guidelines can be useful in an interactive optimization environment and in the design of heuristic rules for the development of knowledge-based expert optimization systems

In situ changes in enzyme activity during Neurospora conidial germination

In situ changes in enzyme activity during Neurospora conidial germinatio

Trace formula for dieletric cavities : I. General properties

The construction of the trace formula for open dielectric cavities is examined in detail. Using the Krein formula it is shown that the sum over cavity resonances can be written as a sum over classical periodic orbits for the motion inside the cavity. The contribution of each periodic orbit is the product of the two factors. The first is the same as in the standard trace formula and the second is connected with the product of reflection coefficients for all points of reflection with the cavity boundary. Two asymptotic terms of the smooth resonance counting function related with the area and the perimeter of the cavity are derived. The coefficient of the perimeter term differs from the one for closed cavities due to unusual high-energy asymptotics of the $\mathbf{S}$-matrix for the scattering on the cavity. Corrections to the leading semi-classical formula are briefly discussed. Obtained formulas agree well with numerical calculations for circular dielectric cavities.Comment: 13 pages, 10 figure