On the distribution function of the complexity of finite sequences

Investigations of complexity of sequences lead to important applications such as effective data compression, testing of randomness, discriminating between information sources and many others. In this paper we establish formulae describing the distribution functions of random variables representing the complexity of finite sequences introduced by Lempel and Ziv in 1976. It is known that this quantity can be used as an estimator of entropy. We show that the distribution functions depend affinely on the probabilities of the so-called “exact” sequences.     

Integrated Data Management for a Fleet of Search‐and‐rescue Robots

Search‐and‐rescue operations have recently been confronted with the introduction of robotic tools that assist the human search‐and‐rescue workers in their dangerous but life‐saving job of searching for human survivors after major catastrophes. However, the world of search and rescue is highly reliant on strict procedures for the transfer of messages, alarms, data, and command and control over the deployed assets. The introduction of robotic tools into this world causes an important structural change in this procedural toolchain. Moreover, the introduction of search‐and‐rescue robots acting as data gatherers could potentially lead to an information overload toward the human search‐and‐rescue workers, if the data acquired by these robotic tools are not managed in an intelligent way. With that in mind, we present in this paper an integrated data combination and data management architecture that is able to accommodate real‐time data gathered by a fleet of robotic vehicles on a crisis site, and we present and publish these data in a way that is easy to understand by end‐users. In the scope of this paper, a fleet of unmanned ground and aerial search‐and‐rescue vehicles is considered, developed within the scope of the European ICARUS project. As a first step toward the integrated data‐management methodology, the different robotic systems require an interoperable framework in order to pass data from one to another and toward the unified command and control station. As a second step, a data fusion methodology will be presented, combining the data acquired by the different heterogenic robotic systems. The computation needed for this process is done in a novel mobile data center and then (as a third step) published in a software as a service (SaaS) model. The SaaS model helps in providing access to robotic data over ubiquitous Ethernet connections. As a final step, we show how the presented data‐management architecture allows for reusing recorded exercises with real robots and rescue teams for training purposes and teaching search‐and‐rescue personnel how to handle the different robotic tools. The system was validated in two experiments. First, in the controlled environment of a military testing base, a fleet of unmanned ground and aerial vehicles was deployed in an earthquake‐response scenario. The data gathered by the different interoperable robotic systems were combined by a novel mobile data center and presented to the end‐user public. Second, an unmanned aerial system was deployed on an actual mission with an international relief team to help with the relief operations after major flooding in Bosnia in the spring of 2014. Due to the nature of the event (floods), no ground vehicles were deployed here, but all data acquired by the aerial system (mainly three‐dimensional maps) were stored in the ICARUS data center, where they were securely published for authorized personnel all over the world. This mission (which is, to our knowledge, the first recorded deployment of an unmanned aerial system by an official governmental international search‐and‐rescue team in another country) proved also the concept of the procedural integration of the ICARUS data management system into the existing procedural toolchain of the search and rescue workers, and this in an international context (deployment from Belgium to Bosnia). The feedback received from the search‐and‐rescue personnel on both validation exercises was highly positive, proving that the ICARUS data management system can efficiently increase the situational awareness of the search‐and‐rescue personnel.     

Neural Network Based Algorithm for Dynamic System Optimization

A class of artificial neural networks with a two‐layer feedback topology to solve nonlinear discrete dynamic optimization problems is developed. Generalized recurrent neuron models are introduced. A direct method to assign the weights of neural networks is presented. The method is based on Bellmann's Optimality Principle and on the interchange of information which occurs during the synaptic chemical processing among neurons. A comparative analysis of the computational requirements is made. The analysis shows advantages of this approach as compared to the standard dynamic programming algorithm. The technique has been applied to several important optimization problems, such as shortest path and control optimal problems.     

Wireless link prediction and triggering using modified Ornstein–Uhlenbeck jump diffusion process

Through time domain observation, typical wireless signal strength values seems to exhibit some forms of mean-reverting and discontinuous “jumps” behaviour. Motivated by this fact, we propose a wireless link prediction and triggering (LPT) technique using a modified mean-reverting Ornstein–Uhlenbeck (OU) jump diffusion process. The proposed technique which we refer as OU-LPT is an integral component of wireless mesh network monitoring system developed by ICT FP7 CARrier grade wireless MEsh Network project. In particular, we demonstrate how this technique can be applied in the context of wireless mesh networks to support link switching or handover in the event of predicted link degradation or failure. The proposed technique has also been implemented and evaluated in a real-time experimental testbed. The results show that OU-LPT technique can significantly enhance the reliability of wireless links by reducing the rate of false triggers compared to a conventional linear prediction technique and therefore offers a new direction on how wireless link prediction, triggering and switching process can be conducted in the future.     

Rheological characteristics of oligomeric semiproducts gained via chemical degradation of polyurethane foam using crude glycerin in the presence of different catalysts

Polyurethane (PU) recycling is a topic of growing interest due to the increasing amount of polyurethane waste. The main purpose of polyurethane chemical recycling is to recover the starting polyol. In this study, a method of polyurethane thermochemical recycling, glycerolysis by means of crude glycerin, is proposed. This work presents a comparative study of commercial catalysts used in order to accelerate the decomposition process, namely triethylamine (TEA), potassium acetate (KAc), 1,4‐diazabicyclo[2.2.2]octane (DABCO), sodium hydroxide (NaOH), dibutyltin dilaurate (DbDl), and stannous octoate (StOc).The effect of used catalyst on the chemical structure and rheological properties was studied. The type of catalyst does not have significant influence on the chemical structure, but causes different course of reaction: split‐ and single‐phase in applied conditions. Glycerolysates were measured by Brookfield Rheometer. It was found that repolyols can be described by the Herschel–Bulkely mathematical model in the best accuracy. The investigation showed that the rheological behavior of glycerolysates depended on the catalyst used in glycerolysis process. POLYM. ENG. SCI., 57:891–900, 2017. © 2016 Society of Plastics Engineers     

A Two-Stage Method for an Approximate Calculation of Statically Indeterminate Trusses

The paper presents the principles of a method, which in two simple stages makes possible to carry out the statically calculation of values of forces acting in the fiat static indeterminate trusses. In each stage, it is considered the static determinate truss, scheme of which is obtained after remove the suitable number of members from the basic static indeterminate truss. The both intermediate statically determinate trusses are of the same clear span and they are loaded by forces of half values applied to the corresponding truss nodes. The method applies one of the typical procedures of calculation of the statically determinate trusses and then it is applied in an appropriate way the rule of superposition for obtaining the final values of forces acting in particular members of the basic truss. The values of forces calculated in this way are of a very close approximation to the force values determined in the special and complex ways being considered as the exact calculation methods. The proposed method can be useful mostly but not only for the initial structural design of such systems. The simplicity of the two-stage method justifies an assumption that it can be relatively easy and worthy to adjust to the requirements of the computer aided technology of statically calculation of the complex forms of trusses.     

Towards the improvement of thermal efficiency in lignite‐fired power generation: Concerning the utilization of Polish lignite deposits in state‐of‐the‐art IGCC technology

Integrated coal Gasification Combined Cycle (IGCC) is the most advanced technology for coal‐fired power generation. The two‐stage entrained flow gasification process allows for the use of a wide range of coal, as long as the gasification temperature is above the ash melting point of a used fuel. In this gasification technology, lignite, which often has a low ash melting point, can be preferably utilized. However, ash fluidity is also another importance, because the behaviour of molten slag can diminish a stable ash discharge from a gasifier. As the eligibility of coal ash properties is a considerable factor, water physically and chemically kept in lignite (30 – 60% in mass) attributes to deteriorating gasification efficiency, because it causes significant heat loss and increasing oxygen consumption. Developing a thermal evaporative lignite drying method will be a necessary attempt to apply lignite to the coal gasification process. For those preceded objectives, coal and ash properties and drying characteristics of several grades of Polish lignite, extracted from Belchatow and Turow deposits, have been experimentally investigated in a preliminary study evaluating the applicability and consideration for its utilization in state‐of‐the‐art clean coal technology, IGCC. This paper particularly discusses the eligibility of Polish lignite from the perspective of the fusibility and fluidity of ash melts and the fundamental drying kinetics of lignite in superheated steam in the light of water removal. The viscosity of ash melts is measured at high temperature up to 1700 °C. In the drying tests, the significant influence of structural issues, because of the provenance and origin of lignite on the drying characteristics, was found by applying the method of sensitivity analysis of physical propensity. This paper concludes that the investigated Polish lignite has characteristics favourable for utilization in IGCC technology, once the precautions related to its high moisture have been carefully addressed. Copyright © 2016 John Wiley & Sons, Ltd.     

A three-dimensional heterogeneity analysis of electrochemical energy conversion in SOFC anodes using electron nanotomography and mathematical modeling

In this paper a fully three dimensional, multiphase, micro-scale solid oxide fuel cell anode transport phenomena numerical model is proposed and verified. The Butler-Volmer model was combined with empirical relations for conductivity and diffusivity - notably the Fuller-Shetler-Giddings equation, and the Fickian model for transport of gas reagents. FIB-SEM tomography of a commercial SOFC stack anode was performed and the resulting images were processed to acquire input data. A novel method for estimating local values of Triple Phase Boundary length density for use in a three-phase, three-dimensional numerical mesh was proposed. The model equations are solved using an in-house code and the results were verified by comparison to an analytical solution within the range of its applicability. A limited parametric study was performed to qualitatively assess simulation performance and impact of heterogeneity. Despite the high dependence of the SOFC anode performance on the geometry of its anisotropic, three-phase microstructure there are very few micro-scale numerical models simulating transport phenomena within these electrodes.