Demo abstract: towards extracting semantics by visualizing large traceroute datasets

Many Internet mapping projects have used traceroute as a measurement primitive and have generated hundreds of millions of traceroute samples used, among many purposes, for network debugging, troubleshooting and Internet mapping. In this work, we advocate the use of visualization as a means to extract semantics from large sets of traceroute data collected from large-scale traceroute campaigns. Using subsets of these datasets consisting of all traceroutes traversing a particular Internet eXchange Point (IXP), we illustrate how visualization allows us to (1) examine existing large datasets in a different way and (2) present different views of the data that can provide new insights and lead to new questions.     

Behaviour of foam concrete under sulphate environments

This paper reports the effects of variation in density, concentration and type of cation associated with sulphate on the expansion, mass and strength loss of foam concrete produced with two synthetic surfactants. Comparisons are made between behaviour of foam concrete of different densities and that of corresponding base mixes of mortar without foam. The investigations indicated that the expansion in sodium sulphate environment was up to 28% higher than that of magnesium sulphate environment which can be attributed to greater quantum of ettringite formation in sodium sulphate environment. The major deterioration mechanism in magnesium sulphate environment is disintegration of cementing material and this contributed to loss in mass of 1% and higher sulphate deterioration factor of 0.4 for specimens under very severe magnesium sulphate environment. Irrespective of the type of sulphate environment, the deterioration of foam concrete was lower than that of base mix.     

Using OpenFlow to provide cut-through switching in MobilityFirst

Mobile devices are expected to become the Internet’s predominant technology. Current protocols such as TCP/IP were not originally designed with mobility as a key consideration, and therefore underperform under challenging mobile and wireless conditions. MobilityFirst, a clean slate architecture proposal, embraces several key concepts centered around secure identifiers that inherently support mobility and trustworthiness as key requirements of the network architecture. This includes a hop-by-hop segmented data transport based on a globally unique identifier. This allows late and dynamic rebinding of end-point addresses to support mobility. While this provides critical gains in wireless segments, some overheads are incurred even in stable segments such as in the core. Bypassing routing-layer decisions in these cases, with lower layer cut-through forwarding, can improve said gains. In this work, we introduce a general bypass capability within the MobilityFirst architecture that provides better performance and enables both individual and aggregate flow-level traffic control. Furthermore, we present an OpenFlow-based proof-of-concept implementation of the bypass function using layer 2 VLAN tagging. We run experiments on the ORBIT and Global Environment for Network Innovations (GENI) testbeds to evaluate the performance and scalability of the solution. By implementing the bypass functionality, we are able to significantly reduce the number of messages processed by the controller as well as the number of flow rules that need to be pushed into the switches.     

EXPERIMENTAL AND ANALYTICAL ESTIMATES OF FATIGUE CRACK CLOSURE IN AN ALUMINIUM-COPPER ALLOY PART II: A FINITE ELEMENT ANALYSIS

Abstract— A numerical investigation of the fatigue crack closure phenomenon has been performed by an elastic-plastic finite element analysis. Computer software was developed to consider many aspects affecting plasticity-induced crack closure. Linear and power-law hardening models are considered in the finite element analysis. The paper presents results from the study carried out on compact tension (CT) coupons at various crack lengths corresponding to different loading conditions. Finally the results of the analysis are compared with the experimental estimates of fatigue crack closure levels obtained from laser interferometry, scanning-electron and transmission-electron fractography presented in Part I of this paper on identical specimens.     

Effectiveness of visual interactive modeling in the context of multiple-criteria Group decisions

Significant research about the impact of information presentation on decision processes, group-decision support systems, and multicriteria decision making has occurred over the past 10 to 15 years. Advances in hardware and software technologies have significantly reduced costs and enhanced information presentation capability, specifically in the areas of virtual reality and visual interactive modeling (VIM). These visualization technologies can aid in the assimilation of complex qualitative and quantitative information by the decision maker and allow the abstraction of vast information space. Thus, in group-decision situations, visualization has the potential to enhance the decision makers' ability to make appropriate tradeoffs and improve communication between group members resulting in quicker and better consensus decisions. This paper focuses on the study of the effectiveness of advanced information-presentation technologies, such as VIM in complex decision situations involving multiple criteria and groups of decision makers. The effectiveness of VIM is evaluated through a controlled experimental study. The study finds that VIM leads to greater efficiency in decision making and improved group-member attitude and satisfaction with the decision-making process and group-decision solution. However, somewhat contrary to our a priori expectations, the quality of the decision that is made by the groups using visual-interaction modeling is not better than those without this support.     

An iterative system equivalent reduction expansion process for extraction of high frequency response from reduced order finite element model

An iterative system equivalent reduction expansion process (SEREP) is proposed for extraction of high frequency response from a reduced-order model (ROM) under frequency band-limited excitation. Various model order reduction methods are discussed. To alleviate the present drawback of the SEREP, which requires computation of full system modal matrix, an iterative method based on Sturm sequence check is proposed. The method uses eigenvalue separation properties on the excitation frequency band to identify the optimal number of the eigenpairs required to capture the accurate response. The basic steps for numerical implementation are given. Numerical results are presented to validate the predicted response. Comparison is also made to explain the reasons for the instability of the ROM based on dynamic condensation to capture the high frequency dynamics. Case studies are carried out to demonstrate the effect of the chosen frequency band for response extraction. Also, it is shown that accurate results are obtained while using the proposed method when the chosen frequency band encompass the excitation frequency band.     

Optimizing amplifier placements in a multiwavelength opticalLAN/MAN: the equally powered-wavelengths case

Wavelength division multiplexing (WDM) provides the ability to utilize the enormous bandwidth offered by optical networks, using today's electronics. WDM-based optical networks employing passive-star couplers have been proposed for deployment in local and metropolitan areas. Optical amplification is often required in such networks to compensate for the signal attenuation along the fiber links and the splitting and coupling losses in the network. However, an optical amplifier has constraints on the maximum gain and the maximum output power it can supply; thus optical amplifier placement becomes a challenging problem. A simplifying assumption for analytical tractability requires that all wavelengths, present at a particular point in a fiber, be at the same power level, viz, the equally powered-wavelengths case. However, previous studies did not minimize the total number of amplifiers while achieving power equalization. In this paper, we formulate the minimization of amplifiers with power equalization as a mixed integer linear program (MILP) that can be solved by a linear program solver. Illustrative examples on sample networks are presented, which demonstrate the characteristics and the advantages of our optimal amplifier placement algorithm