Monotone graph limits and quasimonotone graphs

The recent theory of graph limits gives a powerful framework for understanding the properties of suitable (convergent) sequences $(G_n)$ of graphs in terms of a limiting object which may be represented by a symmetric function $W$ on $[0,1]$, i.e., a kernel or graphon. In this context it is natural to wish to relate specific properties of the sequence to specific properties of the kernel. Here we show that the kernel is monotone (i.e., increasing in both variables) if and only if the sequence satisfies a `quasi-monotonicity' property defined by a certain functional tending to zero. As a tool we prove an inequality relating the cut and $L^1$ norms of kernels of the form $W_1-W_2$ with $W_1$ and $W_2$ monotone that may be of interest in its own right; no such inequality holds for general kernels.Comment: 38 page

Shaking table testing of an existing masonry building: assessment and improvement of the seismic performance

This paper aims to assess and improve the seismic performance of an existing masonry building with flexible floors, representative of a Portuguese building typology—‘gaioleiro’ buildings. The study involved seismic tests and dynamic identification tests of two models (nonstrengthened and strengthened) in the shaking table. Each model was subjected to several seismic tests with increasing amplitude. . Before the first test and after each seismic test, the dynamic identification of the model was carried out, aiming at obtaining their seismic vulnerability curves based on a damage indicator obtained from the decrease of the frequencies of the modes. In the strengthened model, steel elements were used to improve the connection between walls and floors, together with ties in the upper stories. The results show that adopted strengthening technique is effective for reducing the seismic vulnerability of ‘gaioleiro’ buildings, namely for improving the out-of-plane behavior of the facades.The first author acknowledges the financial support from the Portuguese Foundation for Science and Technology (FCT) through grant SFRH/BD/32190/2006. The work was also supported by the project 'New Integrated Knowledge based approaches to the protection of cultural heritage form Earthquake-induced Risk' (NIKER FP7-ENV-2009-1-224123) from the European Commission

Fast matrix computations for pair-wise and column-wise commute times and Katz scores

We first explore methods for approximating the commute time and Katz score between a pair of nodes. These methods are based on the approach of matrices, moments, and quadrature developed in the numerical linear algebra community. They rely on the Lanczos process and provide upper and lower bounds on an estimate of the pair-wise scores. We also explore methods to approximate the commute times and Katz scores from a node to all other nodes in the graph. Here, our approach for the commute times is based on a variation of the conjugate gradient algorithm, and it provides an estimate of all the diagonals of the inverse of a matrix. Our technique for the Katz scores is based on exploiting an empirical localization property of the Katz matrix. We adopt algorithms used for personalized PageRank computing to these Katz scores and theoretically show that this approach is convergent. We evaluate these methods on 17 real world graphs ranging in size from 1000 to 1,000,000 nodes. Our results show that our pair-wise commute time method and column-wise Katz algorithm both have attractive theoretical properties and empirical performance.Comment: 35 pages, journal version of http://dx.doi.org/10.1007/978-3-642-18009-5_13 which has been submitted for publication. Please see http://www.cs.purdue.edu/homes/dgleich/publications/2011/codes/fast-katz/ for supplemental code

Googling the brain: discovering hierarchical and asymmetric network structures, with applications in neuroscience

Hierarchical organisation is a common feature of many directed networks arising in nature and technology. For example, a well-defined message-passing framework based on managerial status typically exists in a business organisation. However, in many real-world networks such patterns of hierarchy are unlikely to be quite so transparent. Due to the nature in which empirical data is collated the nodes will often be ordered so as to obscure any underlying structure. In addition, the possibility of even a small number of links violating any overall “chain of command” makes the determination of such structures extremely challenging. Here we address the issue of how to reorder a directed network in order to reveal this type of hierarchy. In doing so we also look at the task of quantifying the level of hierarchy, given a particular node ordering. We look at a variety of approaches. Using ideas from the graph Laplacian literature, we show that a relevant discrete optimization problem leads to a natural hierarchical node ranking. We also show that this ranking arises via a maximum likelihood problem associated with a new range-dependent hierarchical random graph model. This random graph insight allows us to compute a likelihood ratio that quantifies the overall tendency for a given network to be hierarchical. We also develop a generalization of this node ordering algorithm based on the combinatorics of directed walks. In passing, we note that Google’s PageRank algorithm tackles a closely related problem, and may also be motivated from a combinatoric, walk-counting viewpoint. We illustrate the performance of the resulting algorithms on synthetic network data, and on a real-world network from neuroscience where results may be validated biologically

PELAKSANAAN PROGRAM KEWIRAUSAHAAN DI SMK N 5 PALEMBANG

Penelitian ini mengambil judul “Pelaksanaan Progran Kewirausahaan di SMK Negeri 05 Palembang.” Yang dibahas di dalam skripsi ini adalah pelaksanaan program kewirausahaan dan faktor yang mempengaruhi pelaksanaan program kewirausahaan di SMK Negeri 05 Palembang. Tujuan dari penelitian ini adalah (1) untuk mendeskripsikan bagaimana program kewirausahaan melalui pembelajaran dan praktek di SMK Negeri 05 Palembang, (2) untuk memahami bagaimana Faktor yang mempengaruhi pelaksanaan program kewirausahaan di SMK Negeri 05 palembang. Adapun jenis data dalam penelitian ini menggunakan pendekatan kualitatif dengan jenis penelitian studi kasus, yaitu mengumpulkan data-data yang relevan yang dapat menggambarkan pelaksanaan program kewirausahaan di SMK Negeri 05 Palembang. Subjek yang di teliti adalah para guru dan siswa, untuk memperoleh data yang dibutuhkan, penelitian menggunakan teknik pengumpulan data, melalui observasi, wawancara, dokumentasi. Dari hasil penelitian dapat disimpulkan bahwa dalam pelaksanaan program kewirausahaan di SMK Negeri 05 Palembang, dilakukan melalui 2 tahap, pertama pembelajaran di dalam kelas, yang kedua pembelajaran diluar kelas. Pembelajaran di dalam kelas seperti halnya pembelajaran pada mata pembelajaran yang lainnya, guru menyampaikan materi kemudian siswa memberi tanggapan sesuai dengan kurikulum yang ada saat ini, pembelajaran diluar kelas berupa praktek, prakarya yang dilaksankan pada waktu yang telah di tetapkan. Memanfaatkan kain flannel untuk dibuat kerajinan tangan berupa bunga, hiasan tempat tisu dan hiasan tabungan. Sedangakan faktor yang mempengaruhi program kewirausahaan yaitu ekspektasi pendapatan, keluarga, pendidikan dan kerjasama

Euclidean versus hyperbolic congestion in idealized versus experimental networks

This paper proposes a mathematical justification of the phenomenon of extreme congestion at a very limited number of nodes in very large networks. It is argued that this phenomenon occurs as a combination of the negative curvature property of the network together with minimum length routing. More specifically, it is shown that, in a large n-dimensional hyperbolic ball B of radius R viewed as a roughly similar model of a Gromov hyperbolic network, the proportion of traffic paths transiting through a small ball near the center is independent of the radius R whereas, in a Euclidean ball, the same proportion scales as 1/R^{n-1}. This discrepancy persists for the traffic load, which at the center of the hyperbolic ball scales as the square of the volume, whereas the same traffic load scales as the volume to the power (n+1)/n in the Euclidean ball. This provides a theoretical justification of the experimental exponent discrepancy observed by Narayan and Saniee between traffic loads in Gromov-hyperbolic networks from the Rocketfuel data base and synthetic Euclidean lattice networks. It is further conjectured that for networks that do not enjoy the obvious symmetry of hyperbolic and Euclidean balls, the point of maximum traffic is near the center of mass of the network.Comment: 23 pages, 4 figure

Designing Chatbots for Crises: A Case Study Contrasting Potential and Reality

Chatbots are becoming ubiquitous technologies, and their popularity and adoption are rapidly spreading. The potential of chatbots in engaging people with digital services is fully recognised. However, the reputation of this technology with regards to usefulness and real impact remains rather questionable. Studies that evaluate how people perceive and utilise chatbots are generally lacking. During the last Kenyan elections, we deployed a chatbot on Facebook Messenger to help people submit reports of violence and misconduct experienced in the polling stations. Even though the chatbot was visited by more than 3,000 times, there was a clear mismatch between the users’ perception of the technology and its design. In this paper, we analyse the user interactions and content generated through this application and discuss the challenges and directions for designing more effective chatbots

Effect of geometrical parameters of aluminum-to-steel bolted connections

Abstract : Through experimental and numerical studies, this research work aims to provide directions on the optimal geometric configuration for single-lap and double-lap bolted connection between aluminum alloy 6061-T6 and steel. From experimental test results, the effects of different geometric parameters on the joint strength were discussed. These parameters include the end-distance, the side-distance, the pitch-distance, the plate thickness and the joint eccentricity. Then, the experimental results were compared to predicted results using design references and geometric recommendations proposed by design references were critically examined. The experimental study was complemented by finite element (FE) analysis to extend the study to a larger range of parameters. In addition to the analysis of the geometric parameters listed above, the effects of the gage-distance on the joint strength were studied in the FE analysis. The experimental and finite element results show that a careful selection of geometric parameters can result in the high improvement of the connection strength and failure mode. Limiting the side-distance to the minimum recommended value was found to limit the strength of a connection with two bolts in a column to that of the one-bolt connection. In most cases, bearing was found to govern the strength of the connections. The calculated bearing strengths were found to underestimate significantly the connection strength. Based on these analyses, maximum geometric parameters beyond which there is no further increase of the joint capacity were evaluated and optimum geometric parameters were proposed