Mine maintenance analysis through Markov chain schemes

ABSTRACT

This paper shows how Markov chain schemes can be used for analyzing equipment availability problems, forecasting the number of dozer engines replacements, studying hoist traffic pattern between various levels in an underground mine and modelling the occurence of good and defective idlers along a conveyor.     

The Stratosphere platform for big data analytics

We present Stratosphere, an open-source software stack for parallel data analysis. Stratosphere brings together a unique set of features that allow the expressive, easy, and efficient programming of analytical applications at very large scale. Stratosphere’s features include “in situ” data processing, a declarative query language, treatment of user-defined functions as first-class citizens, automatic program parallelization and optimization, support for iterative programs, and a scalable and efficient execution engine. Stratosphere covers a variety of “Big Data” use cases, such as data warehousing, information extraction and integration, data cleansing, graph analysis, and statistical analysis applications. In this paper, we present the overall system architecture design decisions, introduce Stratosphere through example queries, and then dive into the internal workings of the system’s components that relate to extensibility, programming model, optimization, and query execution. We experimentally compare Stratosphere against popular open-source alternatives, and we conclude with a research outlook for the next years.     

A Monte-Carlo code for the detailed simulation of electron and light-ion tracks in condensed matter

In an effort to understand the basic mechanism of the action of charged particles in solid radiation dosimeters, we extend our Monte-Carlo code (MC4) to condensed media (liquids/solids) and present new track-structure calculations for electrons and protons. Modeling the energy dissipation process is based on a model dielectric function, which accounts in a semi-empirical and self-consistent way for condensed-phase effects which are computationally intractable. Importantly, these effects mostly influence track-structure characteristics at the nanometer scale, which is the focus of radiation action models. Since the event-by-event scheme for electron transport is impractical above several kilo-electron volts, a condensed-history random-walk scheme has been implemented to transport the energetic delta rays produced by energetic ions. Based on the above developments, new track-structure calculations are presented for two representative dosimetric materials, namely, liquid water and silicon. Results include radial dose distributions in cylindrical and spherical geometries, as well as, clustering distributions, which, among other things, are important in predicting irreparable damage in biological systems and prompt electric-fields in microelectronics.     

Development of an FPGA-based system for real-time simulation of photovoltaic modules

Photovoltaic (PV) simulators are indispensable for the operational evaluation of PV energy production system components (e.g. battery chargers, DC/AC inverters, etc.), in order to avoid the time-consuming and expensive field-testing process. In this paper, the development of a novel real-time PV simulator based on Field Programmable Gate Arrays (FPGAs), is presented. The proposed system consists of a Buck-type DC/DC power converter, which is controlled by an FPGA-based unit using the Pulse Width Modulation (PWM) principle. The system operator is able to define both the PV module type to be simulated and the environmental conditions under which the selected PV module operates. The proposed design method enhances the rapid system prototyping capability and enables the reduction of the power converter size and cost due to the high clock speed feature of the FPGA-based control unit. The experimental results indicate that, using the proposed method, the PV module current-voltage characteristics examined are reproduced with an average accuracy of 1.03%.     

Efficiency of Bauxsol™ in Permeable Reactive Barriers to Treat Acid Rock Drainage

Abstract  Permeable reactive barriers (PRBs) and flow-through reaction cells are fairly new passive treatment alternatives to conventional lime treatment of acidic rock drainage (ARD). They are ideal for the treatment of flowing ARD and are particularly useful when contaminants are likely to persist for several years. This paper describes column tests performed to simulate a PRB constructed using Bauxsol™, a chemically and physically treated bauxite refinery residue, as a reactive material. This experimentation shows promising results for the Bauxsol™ PRB method in neutralizing pH and removing metals from acidic mine effluents.     

On optimal cell planning: Case study for a DCS 1800 system

Micro and pico cell planning strategies are adopted in personal communication systems (PCS) in order to increase their capacity. The usage of the upper UHF band in combination with greater bandwidth is already proposed by telecom engineers in order to achieve the promised service quality and data rates. These strategies are characterized by an increased number of cells in specific geographical areas with the corresponding operating base transceiving stations (BTS) located at relatively low heights above the street level. In this case, the cell planning procedure in linear streets under line‐of‐sight (LOS) conditions needs further study concerning the technical characteristics of the PCS. In this paper, the propagation characteristics of a DCS 1800 system are investigated on a theoretical and experimental basis in a specific geographical area (center of Patras City in Northern Pelloponesse). An improved RF propagation model is proposed in order to determine the propagation path losses occurring under certain multipath fading conditions. Hence an optimum determination of a system's cellular area can be achieved. Copyright © 2001 John Wiley & Sons, Ltd.     

Second-gradient plane deformations of ideal fibre-reinforced materials: implications of hyper-elasticity theory

The influence that some new, second-gradient, effects introduced in a recent publication (Spencer and Soldatos, Int J Non-linear Mech 42:355-368, 2007) have on finite plane deformations of ideal fibre-reinforced hyper-elastic solids is investigated. The second-gradient effects are due to the ability of the fibres to resist bending but, in the present case, the constraints of material incompressibility and fibre inextensibility associated with this ideal class of materials offer considerable theoretical simplification. In agreement with its conventional counterpart, where inextensible fibres are perfectly flexible, the present new theoretical development is still associated with kinematics and reaction stresses that are largely independent of the specific type of material behaviour considered. Static equilibrium considerations reveal therefore a manner in which relevant, non-symmetric stress distributions can be determined by solving two simultaneous, first-order linear differential equations. However, the principal interest of this investigation remains within the class of hyper-elastic materials for which two sets of relatively simple constitutive equations are obtained. At this stage of early theoretical development, immediate interest is directed towards the simplest of those sets, namely the set associated with problems where only gradients relevant to the change of the deformed fibre direction are of principal importance. These developments are applied (i) to the classical problem of plane-strain bending of a rectangular block reinforced by a family of straight fibres running parallel to one of its sides; and (ii) to the problem of “area-preserving” azimuthal shear strain of a circular cylindrical tube having its cross-section reinforced by a family of strong fibres. In the particular case in which the fibres are initially straight and aligned with the radii of the tube cross-section, the solution of the latter problem, which is new in the literature, reveals that fibres resist local bending completely. Instead, they remain straight during deformation and force the tube cross-section to undergo area-preserving azimuthal shear by changing their direction.     

The Human In Vivo Biomolecule Corona onto PEGylated Liposomes: A Proof‐of‐Concept Clinical Study

The self‐assembled layered adsorption of proteins onto nanoparticle (NP) surfaces, once in contact with biological fluids, is termed the “protein corona” and it is gradually seen as a determinant factor for the overall biological behavior of NPs. Here, the previously unreported in vivo protein corona formed in human systemic circulation is described. The human‐derived protein corona formed onto PEGylated doxorubicin‐encapsulated liposomes (Caelyx) is thoroughly characterized following the recovery of liposomes from the blood circulation of ovarian carcinoma patients. In agreement with previous investigations in mice, the in vivo corona is found to be molecularly richer in comparison to its counterpart ex vivo corona. The intravenously infused liposomes are able to scavenge the blood pool and surface‐capture low‐molecular‐weight, low‐abundance plasma proteins that cannot be detected by conventional plasma proteomic analysis. This study describes the previously elusive or postulated formation of protein corona around nanoparticles in vivo in humans and illustrates that it can potentially be used as a novel tool to analyze the blood circulation proteome.