Sublinear Algorithms for Approximating String Compressibility

We raise the question of approximating the compressibility of a string with respect to a fixed compression scheme, in sublinear time. We study this question in detail for two popular lossless compression schemes: run-length encoding (RLE) and a variant of Lempel-Ziv (LZ77), and present sublinear algorithms for approximating compressibility with respect to both schemes. We also give several lower bounds that show that our algorithms for both schemes cannot be improved significantly. Our investigation of LZ77 yields results whose interest goes beyond the initial questions we set out to study. In particular, we prove combinatorial structural lemmas that relate the compressibility of a string with respect to LZ77 to the number of distinct short substrings contained in it (its ?th subword complexity , for small ?). In addition, we show that approximating the compressibility with respect to LZ77 is related to approximating the support size of a distribution.     

联合国城

正协调如一在联合国哥本哈根地区总部的诸多机构和功能,均整合进了这座联合国新城,它就坐落在哥本哈根市中心以北的Marmormolen(大理石墩)。3XN的方案,回应了联合国对建筑图腾的诉求,表达出这一组织的价值观和权威性。更值得一提的是,每个团队独立、高效而专业的品质清晰呈现的同时,它们所植根而共荣的价值观也呼之欲出——协调如一。建筑选址在人工岛上,自然同周边环境     

Ants work harder during consensus decision-making in small groups

Individuals derive many benefits from being social, one of which is improved accuracy of decision-making, the so-called ‘wisdom of the crowds’ effect. This advantage arises because larger groups can pool information from more individuals. At present, limited empirical data indicate that larger groups outperform smaller ones during consensus decision-making in human and non-human animals. Inaccurate decisions can lead to significant costs, and we might therefore expect individuals in small groups to employ mechanisms to compensate for the lack of numbers. Small groups may be able to maintain decision accuracy if individuals are better informed than those in larger groups and/or by increasing the proportion of the group involved in collective decision-making relative to larger groups. In this study, we use interactive computer vision software to investigate individual contributions to consensus decision-making during house-hunting in different sized groups of the ant Myrmecina nipponica. We show that individuals in small colonies invest greater effort in the consensus decision process than those in large colonies and should be better informed as a result. This may act to ameliorate the limitations of group size, but could leave smaller groups more susceptible to additional stresses.     

Optimal control of distributed hyperbolic systems with deviating arguments

In this paper optimal control problems for hyperbolic systems in which deviating arguments appear in the integral form both in the state equations and in the boundary conditions are considered. Making use of Lion's scheme, necessary and sufficient conditions of optimality for the Neumann problem are derived. A simple example of application is also provided.     

Decision rules extraction from data stream in the presence of changing context for diabetes treatment

The knowledge extraction is an important element of the e-Health system. In this paper, we introduce a new method for decision rules extraction called Graph-based Rules Inducer to support the medical interview in the diabetes treatment. The emphasis is put on the capability of hidden context change tracking. The context is understood as a set of all factors affecting patient condition. In order to follow context changes, a forgetting mechanism with a forgetting factor is implemented in the proposed algorithm. Moreover, to aggregate data, a graph representation is used and a limitation of the search space is proposed to protect from overfitting. We demonstrate the advantages of our approach in comparison with other methods through an empirical study on the Electricity benchmark data set in the classification task. Subsequently, our method is applied in the diabetes treatment as a tool supporting medical interviews.     

To boldly go: an occam-π mission to engineer emergence

Future systems will be too complex to design and implement explicitly. Instead, we will have to learn to engineer complex behaviours indirectly: through the discovery and application of local rules of behaviour, applied to simple process components, from which desired behaviours predictably emerge through dynamic interactions between massive numbers of instances. This paper describes a process-oriented architecture for fine-grained concurrent systems that enables experiments with such indirect engineering. Examples are presented showing the differing complex behaviours that can arise from minor (non-linear) adjustments to low-level parameters, the difficulties in suppressing the emergence of unwanted (bad) behaviour, the unexpected relationships between apparently unrelated physical phenomena (shown up by their separate emergence from the same primordial process swamp) and the ability to explore and engineer completely new physics (such as force fields) by their emergence from low-level process interactions whose mechanisms can only be imagined, but not built, at the current time.     

Numerical Study of a Thermal Energy Storage Device Utilizing Graphite Foam Infiltrated with a Phase Change Material

Phase change materials (PCM) utilized for energy storage have notoriously low thermal conductivities. As a result, systems based only on a PCM have large internal thermal gradients and slow reaction times making them impractical for most applications. To overcome these issues, various approaches have been utilized to increase the conductivity of the PCM systems. One approach includes the utilization of porous, high thermal conductivity graphite foam infiltrated with a PCM. Here, a numerical approach was employed in order to study the graphite foam/PCM thermal energy storage system (TES). The numerical model was constructed to emulate an experimental set-up allowing for comparisons between the two. The numerical simulation results exhibited accurate time-dependent temperatures at various locations as well as a history of the melt-front’s progression when compared to the experimental data. Due to the model’s successful capture of the transient response of the TES, it is feasible to employ the numerical procedure for designing subsequent thermal energy storage systems.