Influence Maximization: Near-Optimal Time Complexity Meets Practical Efficiency

Given a social network G and a constant k, the influence maximization problem asks for k nodes in G that (directly and indirectly) influence the largest number of nodes under a pre-defined diffusion model. This problem finds important applications in viral marketing, and has been extensively studied in the literature. Existing algorithms for influence maximization, however, either trade approximation guarantees for practical efficiency, or vice versa. In particular, among the algorithms that achieve constant factor approximations under the prominent independent cascade (IC) model or linear threshold (LT) model, none can handle a million-node graph without incurring prohibitive overheads. This paper presents TIM, an algorithm that aims to bridge the theory and practice in influence maximization. On the theory side, we show that TIM runs in O((k+\ell) (n+m) \log n / \epsilon^2) expected time and returns a (1-1/e-\epsilon)-approximate solution with at least 1 - n^{-\ell} probability. The time complexity of TIM is near-optimal under the IC model, as it is only a \log n factor larger than the \Omega(m + n) lower-bound established in previous work (for fixed k, \ell, and \epsilon). Moreover, TIM supports the triggering model, which is a general diffusion model that includes both IC and LT as special cases. On the practice side, TIM incorporates novel heuristics that significantly improve its empirical efficiency without compromising its asymptotic performance. We experimentally evaluate TIM with the largest datasets ever tested in the literature, and show that it outperforms the state-of-the-art solutions (with approximation guarantees) by up to four orders of magnitude in terms of running time. In particular, when k = 50, \epsilon = 0.2, and \ell = 1, TIM requires less than one hour on a commodity machine to process a network with 41.6 million nodes and 1.4 billion edges.Comment: Revised Sections 1, 2.3, and 5 to remove incorrect claims about reference [3]. Updated experiments accordingly. A shorter version of the paper will appear in SIGMOD 201

Tim Hamborsky v. Thomas O\u27Barto

USDC for the Western District of Pennsylvani

Work Stress among Professionals in the Building Construction Industry in Nigeria

This study was undertaken to identify key stress factors among professionals in the building construction industry in Nigeria. This is in view of the fact that to date, very little is known about work stress among professionals in the building construction industry in this country. The study involved the administration of a questionnaire to 107 professionals including architects, builders, civil/structural engineers and quantity surveyors randomly selected from 60 ongoing building projects in Anambra, Ogun and Kaduna States, Nigeria. The data were analysed using descriptive statistics, and findings show that the principal sources of stress were high volume of work, uncomfortable site offices, lack of feedback on previous and ongoing building projects, and variations in the scope of work in ongoing building projects. The paper suggests that taking responsibility for work which one has adequate capacity to handle, establishing realistic budgets and time frames for project delivery, provision of spatially adequate, visually and thermally comfortable site offices, adoption of appropriate job design practices and education of professionals in stress management will reduce the incidence of stress among professionals in the building industry in Nigeria

First-principles studies of water adsorption on graphene: The role of the substrate

We investigate the electronic properties of graphene upon water adsorption and study the influence of the SiO2 substrate in this context using density functional calculations. Perfect suspended graphene is rather insensitive to H2O adsorbates, as doping requires highly oriented H2O clusters. For graphene on a defective SiO2 substrate, we find a strongly different behavior: H2O adsorbates can shift the substrate's impurity bands and change their hybridization with the graphene bands. In this way, H2O can lead to doping of graphene for much lower adsorbate concentrations than for free hanged graphene. The effect depends strongly on the microscopic substrate properties.Comment: 4 pages, 3 figure

Time to Raise the Bar: The Real Corporate Social Responsibility Report for the Hershey Company

This document is part of a digital collection provided by the Martin P. Catherwood Library, ILR School, Cornell University, pertaining to the effects of globalization on the workplace worldwide. Special emphasis is placed on labor rights, working conditions, labor market changes, and union organizing.ILRF_Time_to_Raise_the_Bar_Hershey.pdf: 2396 downloads, before Oct. 1, 2020