Structural efficiency of percolation landscapes in flow networks

Complex networks characterized by global transport processes rely on the presence of directed paths from input to output nodes and edges, which organize in characteristic linked components. The analysis of such network-spanning structures in the framework of percolation theory, and in particular the key role of edge interfaces bridging the communication between core and periphery, allow us to shed light on the structural properties of real and theoretical flow networks, and to define criteria and quantities to characterize their efficiency at the interplay between structure and functionality. In particular, it is possible to assess that an optimal flow network should look like a "hairy ball", so to minimize bottleneck effects and the sensitivity to failures. Moreover, the thorough analysis of two real networks, the Internet customer-provider set of relationships at the autonomous system level and the nervous system of the worm Caenorhabditis elegans --that have been shaped by very different dynamics and in very different time-scales--, reveals that whereas biological evolution has selected a structure close to the optimal layout, market competition does not necessarily tend toward the most customer efficient architecture.Comment: 8 pages, 5 figure

Structural Changes in India's Stock Markets' Efficiency

This paper finds evidence that the Indian stock market has become weak-form efficient, off-late. We proceed by, first, locating structural breaks in the index using Bai-Perron's method for endogenous multiple structural changes. Four structural breaks are identified for the period 1991 to 2008 for the S&P CNX Nifty series -- December 1994, July 1999, June 2003 and January 2006. For this period the behaviour of returns approximates a Stable Paretian distribution. This would mean that the market risk will be beyond that can be predicted by measures build on the assumption of normality of returns. The property of infinite population variance of a stable paretian distribution makes variance based estimators redundant. Therefore, using non-parametric methods the paper tests the efficiency of the market across the periods of structural breaks. It is found that the markets have become weak-form efficient only since the second half of 2003, corresponding to the period of the third structural break.Efficient Markets Hypothesis; Indian Stock Market; Structural Break; Bai-Perron; Paretian Distribution; Runs test;

Structural Changes in India's Stock Markets' Efficiency

This paper finds evidence that the Indian stock market has become weak-form efficient, off-late. We proceed by, first, locating structural breaks in the index using Bai-Perron's method for endogenous multiple structural changes. Four structural breaks are identified for the period 1991 to 2008 for the S&P CNX Nifty series -- December 1994, July 1999, June 2003 and January 2006. For this period the behaviour of returns approximates a Stable Paretian distribution. This would mean that the market risk will be beyond that can be predicted by measures build on the assumption of normality of returns. The property of infinite population variance of a stable paretian distribution makes variance based estimators redundant. Therefore, using non-parametric methods the paper tests the efficiency of the market across the periods of structural breaks. It is found that the markets have become weak-form efficient only since the second half of 2003, corresponding to the period of the third structural break.Efficient Markets Hypothesis; Indian Stock Market; Structural Break; Bai-Perron; Paretian Distribution; Runs test;

Active controls technology to maximize structural efficiency

The implication of the dependence on active controls technology during the design phase of transport structures is considered. Critical loading conditions are discussed along with probable ways of alleviating these loads. Why fatigue requirements may be critical and can only be partially alleviated is explained. The significance of certain flutter suppression system criteria is examined

Structural efficiency study of composite wing rib structures

A series of short stiffened panel designs which may be applied to a preliminary design assessment of an aircraft wing rib is presented. The computer program PASCO is used as the primary design and analysis tool to assess the structural efficiency and geometry of a tailored corrugated panel, a corrugated panel with a continuous laminate, a hat stiffened panel, a blade stiffened panel, and an unstiffened flat plate. To correct some of the shortcomings in the PASCO analysis when shear is present, a two step iterative process using the computer program VICON is used. The loadings considered include combinations of axial compression, shear, and lateral pressure. The loading ranges considered are broad enough such that the designs presented may be applied to other stiffened panel applications. An assessment is made of laminate variations, increased spacing, and nonoptimum geometric variations, including a beaded panel, on the design of the panels

The Performance of German Water Utilities: A (Semi)-Parametric Analysis

Germany's water supply industry is characterized by a multitude of utilities and widely diverging prices, possibly resulting from structural differences beyond the control of firms' management, but also from inefficiencies. In this article we use Data Envelopment Analysis and Stochastic Frontier Analysis to determine the utilities' technical efficiency scores based on cross-sectional data from 373 public and private water utilities in 2006. We find large differences in technical efficiency scores even after accounting for significant structural variables like network density, share of groundwater usage and water losses.Water supply, technical efficiency, data envelopment analysis, stochastic frontier analysis, structural variables, bootstrapped truncated regression

Probabilistic structural analysis algorithm development for computational efficiency

The PSAM (Probabilistic Structural Analysis Methods) program is developing a probabilistic structural risk assessment capability for the SSME components. An advanced probabilistic structural analysis software system, NESSUS (Numerical Evaluation of Stochastic Structures Under Stress), is being developed as part of the PSAM effort to accurately simulate stochastic structures operating under severe random loading conditions. One of the challenges in developing the NESSUS system is the development of the probabilistic algorithms that provide both efficiency and accuracy. The main probability algorithms developed and implemented in the NESSUS system are efficient, but approximate in nature. In the last six years, the algorithms have improved very significantly

The collection efficiency of the Value Added Tax: Theory and international evidence

This paper evaluates the political economy and structural factors explaining the collection efficiency of the Value Added Tax (VAT), where the collection efficiency is determined by the probability of audit and by the penalty on underpaying, and implementation lags imply that the present policy maker determines the efficiency of the tax system next period. Theory suggests that the collection efficiency is affected by political economy considerations - greater polarization and political instability would reduce the efficiency of the tax collection, and collection is impacted by structural factors affecting the ease of tax evasion (such as urbanization, agriculture share, openness). We evaluate the VAT collection efficiency (VAT revenue over the aggregate consumption divided by the standard VAT rate) in a panel of 44 countries over 1970-99. A one standard deviation increase in durability of political regime, and in the ease and fluidity of political participation, increases the VAT collection efficiency by 3.1% and 3.6%, respectively. A one standard deviation increase in urbanization, trade openness and the share of agriculture, changes the VAT collection efficiency by 12.7%, 3.9% and -4.8%, respectively. Qualitatively identical results apply for the ratio of VAT revenue to GDP divided by the standard VAT

Measurement of dynamic efficiency, a directional distance function parametric approach

This research proposes a parametric estimation of the structural dynamic efficiency measures proposed by Silva and Oude Lansink (2009). Overall, technical and allocative efficiency measurements are derived based on a directional distance function and the duality between this function and the optimal value function. The applicability of the parametric proposal is illustrated by assessing dynamic efficiency ratings for a sample of Dutch dairy farms observed from 1995 to 2005.structural dynamic efficiency, dairy farms, parametric approach, Agricultural and Food Policy, Farm Management, Land Economics/Use, D21, D24, D61, D92,