Towards a smooth design process for static communicative node‐link diagrams

Node‐link infographics are visually very rich and can communicate messages effectively, but can be very difficult to create, often involving a painstaking and artisanal process. In this paper we present an investigation of node‐link visualizations for communication and how to better support their creation. We begin by breaking down these images into their basic elements and analyzing how they are created. We then present a set of techniques aimed at improving the creation workflow by bringing more flexibility and power to users, letting them manipulate all aspects of a node‐link diagram (layout, visual attributes, etc.) while taking into account the context in which it will appear. These techniques were implemented in a proof‐of‐concept prototype called GraphCoiffure, which was designed as an intermediary step between graph drawing/editing software and image authoring applications. We describe how GraphCoiffure improves the workflow and illustrate its benefits through practical examples.     

On matrices, automata, and double counting in constraint programming

Matrix models are ubiquitous for constraint problems. Many such problems have a matrix of variables $\mathcal{M}$ , with the same constraint C defined by a finite-state automaton $\mathcal{A}$ on each row of $\mathcal{M}$ and a global cardinality constraint $\mathit{gcc}$ on each column of $\mathcal{M}$ . We give two methods for deriving, by double counting, necessary conditions on the cardinality variables of the $\mathit{gcc}$ constraints from the automaton $\mathcal{A}$ . The first method yields linear necessary conditions and simple arithmetic constraints. The second method introduces the cardinality automaton, which abstracts the overall behaviour of all the row automata and can be encoded by a set of linear constraints. We also provide a domain consistency filtering algorithm for the conjunction of lexicographic ordering constraints between adjacent rows of $\mathcal{M}$ and (possibly different) automaton constraints on the rows. We evaluate the impact of our methods in terms of runtime and search effort on a large set of nurse rostering problem instances.     

Standardising vulnerability categories

Each vulnerability scanner (VS) represents, identifies and classifies vulnerabilities in its own way, thus making the different scanners difficult to study and compare. Despite numerous efforts by researchers and organisations to solve the disparity in vulnerability names used in the different VSs, vulnerability categories have still not been standardised. This paper highlights the importance of having a standard vulnerability category set. It also outlines an approach towards achieving this goal by generating a standard set of vulnerability categories. A data-clustering algorithm that employs artificial intelligence is used for this purpose. The significance of this research results from having an intelligent technique that aids in the generation of standardised vulnerability categories in a relatively fast way. In addition, the technique is generic in the sense that it allows one to accommodate any VS currently known on the market to create such vulnerability categories. Another benefit is that the approach followed in this paper allows one to also compare various VSs currently available on the market. A prototype is presented to verify the concept.     

Efficient product sampling using hierarchical thresholding

We present an efficient method for importance sampling the product of multiple functions. Our algorithm computes a quick approximation of the product on the fly, based on hierarchical representations of the local maxima and averages of the individual terms. Samples are generated by exploiting the hierarchical properties of many low-discrepancy sequences, and thresholded against the estimated product. We evaluate direct illumination by sampling the triple product of environment map lighting, surface reflectance, and a visibility function estimated per pixel. Our results show considerable noise reduction compared to existing state-of-the-art methods using only the product of lighting and BRDF.     

Monotony properties of connected visible graph searching

Search games are attractive for their correspondence with classical width parameters. For instance, the invisible search number (a.k.a. node search number) of a graph is equal to its pathwidth plus 1, and the visible search number of a graph is equal to its treewidth plus 1. The connected variants of these games ask for search strategies that are connected, i.e., at every step of the strategy, the searched part of the graph induces a connected subgraph. We focus on monotone search strategies, i.e., strategies for which every node is searched exactly once. The monotone connected visible search number of an n-node graph is at most O(logn) times its visible search number. First, we prove that this logarithmic bound is tight. Precisely, we prove that there is an infinite family of graphs for which the ratio monotone connected visible search number over visible search number is Ω(logn). Second, we prove that, as opposed to the non-connected variant of visible graph searching, “recontamination helps” for connected visible search. Precisely, we prove that, for any k4, there exists a graph with connected visible search number at most k, and monotone connected visible search number >k     

Toward a formal specification of multimedia synchronization scenarios

This paper introduces time stream Pétri nets (Ts treamPn), a model for the formal specification of multimedia synchronization scenarios. This new model extends time Pétri nets to formally describe the timed behaviour of multimedia objects and streams in asynchronous distributed systems. The proposed approach uses time intervals to label the arcs exiting from the places of the net, and typed transitions to define different firing rules. This model allows a complete and accurate specification of synchronization constraints between multimedia streams and can be used at different levels of granularity.     

Termination of rewrite systems by elementary interpretations

We focus on termination proofs of rewrite systems, especially of rewrite systems containing associative and commutative operators. We prove their termination by elementary interpretations, more specifically, by functions defined by addition, multiplication and exponentiation. We discuss a method based on polynomial interpretations and propose an implementation of a mechanisation of the comparison of expressions built with polynomials and exponentials.     

碳化硅器件挑战现有封装技术

碳化硅(SiC)器件的新特性和移动应用的功率密度要求给功率器件的封装技术提出了新的挑战。现有功率器件的封装技术主要是在硅基的绝缘栅双极晶体管(Insulated Gate Bipolar Transistor,IGBT)和金属氧化物半导体场效应晶体管(Metal Oxide Semiconductor Field Effect Transistor,MOSFET)等基础上发展起来的,并一直都在演进,但这些渐进改良尚不足以充分发挥SiC器件的性能,因而封装技术需要革命性的进步。在简述现有封装技术及其演进的基础上,主要从功率模块的角度讨论了封装技术的发展方向。同时讨论了功率模块的新型叠层结构以及封装技术的离散化、高温化趋势,并对SiC器件封装技术的发展方向做出了综合评估。     

High Q 2D-length extension mode resonators for potential time–frequency applications

Microsystem Technologies - This paper presents recent advances on two dimensional length-extension mode (2D-LEM) quartz resonators providing high quality (Q) factor on resonances at a few MHz. The...     

CBAC4C: conflict-based VM isolation control for cloud computing

For businesses to benefit from the many opportunities of cloud computing, they must first address a number of security challenges, such as the potential leakage of confidential data to unintended third parties. An inter-VM (where VM is virtual machine) attack, also known as cross-VM attack, is one threat through which cloud-hosted confidential data could be leaked to unintended third parties. An inter-VM attack exploits vulnerabilities between co-resident guest VMs that share the same cloud infrastructure. In an attempt to stop such an attack, this paper uses the principles of logical analysis to model a solution that provides physical separation of VMs belonging to conflicting tenants based on their levels of conflict. The derived mathematical model is founded on scientific principles and implemented using four conflict-aware VM placement algorithms. The resultant algorithms consider a tenant's risk appetite and cost implications. The model offers guidance to VM placement and is validated using a proof of concept. A cloud simulation tool was used to test and evaluate the effectiveness and efficiency of the model. The findings reflect that the introduction of the proposed model introduced a time lag in the time it took to place VM instances. On top of this, it was also discovered that the number and size of the VM instances has an effect on the VM placement performance. The findings further illustrate that the conflict tolerance level of a VM has a direct impact on the time it took to place.