Interplay between function and structure in complex networks

We show that abrupt structural transitions can arise in functionally optimal networks, driven by small changes in the level of transport congestion. Our results offer an explanation as to why so many diverse species of network structure arise in Nature (e.g. fungal systems) under essentially the same environmental conditions. Our findings are based on an exactly solvable model system which mimics a variety of biological and social networks. We then extend our analysis by introducing a novel renormalization scheme involving cost motifs, to describe analytically the average shortest path across multiple-ring-and-hub networks. As a consequence, we uncover a 'skin effect' whereby the structure of the inner multi-ring core can cease to play any role in terms of determining the average shortest path across the network.Comment: Expanded version of physics/0508228 with additional new result

Updated Methods for Traffic Impact Analysis, Including Evaluation of Innovative Intersection Designs: Volume I—Technical Report

In 1992, an Applicant’s Guide and a Reviewer’s Guide to Traffic Impact Analyses to standardize the methodologies for conducting traffic impact analyses (TIAs) in Indiana were developed for the Indiana Department of Transportation (INDOT). The methodologies were meant to help streamline the process of preparing and reviewing TIAs. The methodology is applicable for other transportation and government entities as well. Because 20 years have passed since the publication of the guides, INDOT wished to evaluate how effective the guides have been, determine what in the guides has worked well, revise parts of the guides that have not worked well, and add improvements and changes that have occurred since the guides’ publication. Brief explanations of innovative intersection alternatives such as roundabouts, median U-turns (MUT), restricted-crossing U-turns (RCUT), displaced left-turns (DLT), and quadrant roadways (QR) are provided to increase awareness of these possible designs. Some of the innovative designs were compared against a two-way stop-controlled intersection and a conventional signalized intersection for varying volumes on minor street approaches. The median U-turn design seemed to perform better at higher, more balanced flows whereas the roundabout performed better for unbalanced flows. At times, a development affects roads in more than one jurisdiction. Ideas are presented that may facilitate the inclusion of all affected parties early in the development process to improve communication, address all possible effects of the development and better satisfy all affected parties

Updated Methods for Traffic Impact Analysis, Including Evaluation of Innovative Intersection Designs: Volume II—Applicant’s Guide

The INDOT Applicant’s Guide to Traffic Impact Analysis (TIA) is a product of SPR-3605 Updated Methods for Traffic Impact Analysis . The purpose of this study was to review the Applicant’s and Reviewer’s Guides that were published in 1992 and make changes that would bring them in line with the methods and conditions that have emerged since then. This guide is intended to establish a standard framework for traffic impact analysis within Indiana, increasing consistency in study requests, preparation and review. A standardized procedure will enable the TIA study preparer to present the study findings and recommendations in a systematic manner consistent with the reviewer\u27s expectations. The guide is not intended to make things more complicated and time-consuming. On the contrary, with a standard framework, the time involved in the process will decrease for both parties. The Applicant\u27s Guide allows enough flexibility to the study preparer to use innovative methods based on sound engineering judgment and the conditions at a specific site. However, this should be done with the prior consent of the study reviewer(s)

Updated Methods for Traffic Impact Analysis, Including Evaluation of Innovative Intersection Designs: Volume III—Reviewer’s Guide

The INDOT Reviewer’s Guide to Traffic Impact Analysis (TIA) is a product of SPR-3605 Updated Methods for Traffic Impact Analysis. It is intended to provide guidance to individuals who are charged with the responsibility to evaluate the Traffic Impact Analysis (TIA) reports submitted to INDOT (or other public agencies). This guide replaces the 1992 Reviewer\u27s Guide for Traffic Impact Studies. The 1992 Guide was essentially an extended version of the 1992 Applicant\u27s Guide to Traffic Impact Studies. This time, the Reviewer’s Guide is written with the knowledge that the Applicant’s Guide is available to both applicants and reviewers. The 2013 Reviewer’s Guide focuses on added information that may help the reviewer assess the TIA report contents

Fluid and Diffusion Limits for Bike Sharing Systems

Bike sharing systems have rapidly developed around the world, and they are served as a promising strategy to improve urban traffic congestion and to decrease polluting gas emissions. So far performance analysis of bike sharing systems always exists many difficulties and challenges under some more general factors. In this paper, a more general large-scale bike sharing system is discussed by means of heavy traffic approximation of multiclass closed queueing networks with non-exponential factors. Based on this, the fluid scaled equations and the diffusion scaled equations are established by means of the numbers of bikes both at the stations and on the roads, respectively. Furthermore, the scaling processes for the numbers of bikes both at the stations and on the roads are proved to converge in distribution to a semimartingale reflecting Brownian motion (SRBM) in a $N^{2}$-dimensional box, and also the fluid and diffusion limit theorems are obtained. Furthermore, performance analysis of the bike sharing system is provided. Thus the results and methodology of this paper provide new highlight in the study of more general large-scale bike sharing systems.Comment: 34 pages, 1 figure

The Mobility Enterprise - Improving Auto Productivity

The Mobility Enterprise is a particular version of a shared vehicle fleet, aimed at solving the problem of low automobile productivity. The automobile consumes a large portion of America’s transportation energy supply. It also operates much of the time with unused capacity: vacant seats and empty cargo space. Since programs to fill those vacant seats —ride sharing and high occupancy vehicle incentives —have fallen so far short of their objectives, a new approach is warranted. The enterprise’s central concept is matching vehicle attributes to travel needs. Generally, a household purchases vehicles for those few trips that require a large capacity, rather than for the majority of trips (usually to work) that have minimal vehicular needs. If a household could tailor its “immediate access” fleet to these frequent trips and still retain reasonable access to larger-capacity special purpose vehicles (SPV’s), considerable economies could be achieved. The household is relieved of owning seldom-used excess capacity, and automobile productivity and efficiency are greatly improved. Having easy access to a shared fleet of SPV’s also affords a household an increase in the quality and economy of its travel experiences. This paper describes a research project recently begun at Purdue that involves a comprehensive investigation of the Mobility Enterprise concept. Questions of institutional barriers, consumer response, and organization and management are discussed here as keys to the fate of the enterprise in the transportation climate of the foreseeable future

Gene induction during differentiation of human monocytes into dendritic cells: an integrated study at the RNA and protein levels

Changes in gene expression occurring during differentiation of human monocytes into dendritic cells were studied at the RNA and protein levels. These studies showed the induction of several gene classes corresponding to various biological functions. These functions encompass antigen processing and presentation, cytoskeleton, cell signalling and signal transduction, but also an increase in mitochondrial function and in the protein synthesis machinery, including some, but not all, chaperones. These changes put in perspective the events occurring during this differentiation process. On a more technical point, it appears that the studies carried out at the RNA and protein levels are highly complementary.Comment: website publisher: http://www.springerlink.com/content/ha0d2c351qhjhjdm