Controlling a random population

Bertrand et al. introduced a model of parameterised systems, where each agent is represented by a finite state system, and studied the following control problem: for any number of agents, does there exist a controller able to bring all agents to a target state? They showed that the problem is decidable and EXPTIME-complete in the adversarial setting, and posed as an open problem the stochastic setting, where the agent is represented by a Markov decision process. In this paper, we show that the stochastic control problem is decidable. Our solution makes significant uses of well quasi orders, of the max-flow min-cut theorem, and of the theory of regular cost functions. We introduce an intermediate problem of independence interest called the sequential flow problem and study its complexity.

Balkan Migration Crisis and its Impact on Tourism

This paper attempts to quantify, understand and analyse the effect of the migrant flows upon tourism destinations, considering the funnel theory, as a system, focusing on the beginning (inputs), through (throughput) and at the end of the funnel (outputs). Empirically, the research examines three key questions: 1. Importance of tourism economically to countries in the West Balkan Migrant Corridor; 2. Intensive nature of tourism for these countries; 3. Socio-economic consequences of the migrant flows. The crisis and its effects on tourism looks at a funnel that transmits migrants from the Aegean Sea through the West Balkans to North-West Europe. Importantly, the funnel crisis points are in Greece (beginning) and in Germany (end); the intermediate problem areas (Macedonia, Serbia, Croatia, Slovenia) have been in the throughput of the migrants through the funnel. It must also take account of the security situation in Turkey as well as the difficulty of EU member states in assimilating migrants on the route. Based on the results of the research conducted to date, with the sectional sample data from 2014-2017, it is possible to affirm that the migration crisis in West Balkans countries and countries connected to the migrant corridor has impacted only marginally on tourism. However, This problem is socioeconomic yet deeply humanitarian; whilst unfortunate to reduce a deeply disturbing human issue, such an analysis of “people-flows through the funnel” allows an attempt to quantify, understand and analyse the effect of the migrant flows upon tourism destinations.

Treatment of yellow water by membrane separations and advanced oxidation methods

Comparative experimental study is performed on purification of yellow wastewaters separated and collected in solarCity, Linz, Austria. Three membrane methods (micro-, ultra-, and nano-filtration), and two advanced oxidations (gamma radiation and electrochemical oxidation) were applied. Best results concerning the removal of pharmaceuticals and hormones from urine by membrane separation were achieved using the membrane NF-200 (FilmTecTM). Pharmaceuticals (ibuprofen and diclofenac), and hormones (oestrone, β-oestradiol, ethenyloestradiol, oestriol) were removed completely from urine. NF-separation also has some disadvantages: losses of urea, and lowering the conductivity in the product (permeate). The retentates (concentrates) received have to be treated further by oxidation to destroy the “problem” compounds. The results showed that electrochemical oxidation is more suitable than gamma radiation. Gamma-radiation with intensities higher than 10 kGy has to be applied for efficiently destroying of ibuprofen, and especially diclofenac. A high quantity of intermediate “problem” substances with oestrone structure was formed during the gamma oxidation of hormone containing urine samples. The electrochemical oxidation can be successfully applied for elimination of pharmaceuticals such as diclofenac, and hormones (oestrone, β-oestradiol) from yellow wastewater without loss of urea (nitrogen fertiliser).

Hereditary History Preserving Bisimilarity is Undecidable

We show undecidability of hereditary history preserving bisimilarity<br />for finite asynchronous transition systems by a reduction from the halting<br />problem of deterministic 2-counter machines. To make the proof more<br />transparent we introduce an intermediate problem of checking domino<br />bisimilarity for origin constrained tiling systems. First we reduce the<br />halting problem of deterministic 2-counter machines to origin constrained<br />domino bisimilarity. Then we show how to model domino bisimulations as<br />hereditary history preserving bisimulations for finite asynchronous transitions<br />systems. We also argue that the undecidability result holds for<br />finite 1-safe Petri nets, which can be seen as a proper subclass of finite<br />asynchronous transition systems.

Hereditary History Preserving Simulation is Undecidable

We show undecidability of hereditary history preserving simulation<br />for finite asynchronous transition systems by a reduction from the halting<br />problem of deterministic Turing machines. To make the proof more<br />transparent we introduce an intermediate problem of deciding the winner<br />in domino snake games. First we reduce the halting problem of deterministic<br />Turing machines to domino snake games. Then we show how to<br />model a domino snake game by a hereditary history simulation game on<br />a pair of finite asynchronous transition systems.

Component Modal Synthesis Methods Based on Hybrid Models, Part I: Theory of Hybrid Models and Modal Truncation Methods

The assembly of structures along continuous boundaries poses great difficulties for expressing generalized boundary coordinates in modal synthesis, especially in the context of experiments. In order to solve such problems, a hybrid modal synthesis method is proposed in this study. This approach is based on the intermediate problem theory of Weinstein and brings out the duality between the formulation in displacement and the formulation in force. Generalized boundary coordinates are defined by introducing static deformations resulting from force distribution or displacement distribution along the boundaries depending on which formulation is to be used. By introducing integral operators associated with intermediate problems, two new methods of modal truncation can be proposed.

Using Data Tables to Represent and Solve Multiplicative Story Problems

This study tested the effectiveness of an experimental instructional strategy for writing arithmetic sentences for simple multiplication and division story problems involving nonintegral factors. The experimental strategy consisted of building an intermediate problem representation to display the problem quantities in the form of a data table and using multiplicative reasoning. This strategy was compared with a traditional strategy of solving an analogous problem with simpler numbers. Five intact seventh-grade classes participated in the study. Significant effects in favor of the experimental group were found on an intermediate test and a posttest.

Choosing the best of the current crop

A best choice problem is presented which is intermediate between the constraints of the ‘no-information’ problem (observe only the sequence of relative ranks) and the demands of the ‘full-information’ problem (observations from a known continuous distribution). In the intermediate problem prior information is available in the form of a ‘training sample’ of size m and observations are the successive ranks of the n current items relative to their predecessors in both the current and training samples.Optimal stopping rules for this problem depend on m and n essentially only through m + n; and, as m/(m + n) → t, their success probabilities, P*(m, n), converge rapidly to explicitly derived limits p*(t) which are the optimal success probabilities in an infinite version of the problem. For fixed n, P*(m, n) increases with m from the ‘no-information’ optimal success probability to the ‘full-information’ value for sample size n. And as t increases from 0 to 1, p*(t) increases from the ‘no-information’ limit e–1 ≍ 0·37 to the ‘full-information’ limit ≍0·58. In particular p*(0·5) ≍ 0·50.