Simultaneous scheduling of football games and referees using Turkish league data

Assignment decisions of referees to football (soccer) games are highly debated in sports media. Referee assignments are typically done on a weekly basis as the league progresses. However, this practice ignores important workload constraints on referees. Moreover, referees' skill levels should also be considered in determining their assignments. In this article, we first give a mixed integer linear program formulation for the problem of simultaneously generating a game schedule and assigning main referees to games by incorporating specific rules in the Turkish league. We also approach this problem using a genetic algorithm (GA) because of the computational difficulties in solving the problem. In the GA solution pool, we suggest using templates for referee assignments that follow several referee‐related workload constraints. We explain how these templates can be obtained by solving a mixed integer linear model prior to running the GA. The usage of these templates for referee assignments is conceptually similar to using a basic match schedule for game scheduling such as the one used in the Turkish Football League. We use the Turkish Football League fixtures for 2010–2013 as a case study. Experiments with the GA using real‐world data show a rather modest performance in terms of computation time and objective function value. Our numerical results indicate that the problem is extremely hard to solve.     

Stability and performance improvement of extremum seeking control with sliding mode

Extremum seeking control is an adaptive control strategy for a system to iteratively extremize a function in real-time. In this paper we investigate stability and performance improvement by using sliding mode concepts in extremum seeking controllers.     

Portable PEM fuel cell‐ultracapacitor system: Model and experimental verification

This paper presents a comparative study between a model of portable direct hydrogen‐fed proton exchange membrane fuel cell‐ultracapacitor (PEMFC‐UC) power source and experimental results obtained from an actual PEMFC‐UC system in the authors' laboratory. In the proposed system the UC is directly connected to the PEMFC output terminals. The UC is used to supply the power mismatch during the sudden load variations when the load is higher than the PEMFC maximum capacity. The model is then used to estimate the output voltage and study the transient response of the PEMFC‐UC system when subjected to rapid changes in the load. To validate the model, laboratory experiments are carried out using a 100 W commercially available PEMFC and an UC. The model results are verified against the experimental data using three statistical indices to measure the variations, unbiasedness, and accuracy. The indices indicate a maximum difference of 1.06%, which shows a close agreement between the voltage and power responses of the proposed model and the actual PEMFC‐UC system. Copyright © 2009 John Wiley & Sons, Ltd.     

Dynamic modeling and simulation of air-breathing proton exchange membrane fuel cell

Small fuel cells have shown excellent potential as alternative energy sources for portable applications. One of the most promising fuel cell technologies for portable applications is air-breathing fuel cells. In this paper, a dynamic model of an air-breathing PEM fuel cell (AB-PEMFC) system is presented. The analytical modeling and simulation of the air-breathing PEM fuel cell system are verified using Matlab, Simulink and SimPowerSystems Blockset. To show the effectiveness of the proposed AB-PEMFC model, two case studies are carried out using the Matlab software package. In the first case study, the dynamic behavior of the proposed AB-PEMFC system is compared with that of a planar air-breathing PEM fuel cell model. In the second case study, the validation of the air-breathing PEM fuel cell-based power source is carried out for the portable application. Test results show that the proposed AB-PEMFC system can be considered as a viable alternative energy sources for portable applications.     

Portable direct hydrogen fed PEM fuel cell model and experimental verification

This paper focuses on the experimental verification of an electrochemical model of 100 W portable direct hydrogen fed proton exchange membrane (PEM) fuel cell (FC). The model is built based on the relationship between the FC terminal voltage and the partial pressures of hydrogen and oxygen. The model is then used to predict the output voltage and study the transient response of a PEMFC when subjected to rapid changes in the load. To validate the model, the measurements obtained from a commercially available 100 W FC are compared against the model results. Three different scenarios are considered for testing the model and the actual FC. In the first two scenarios, a step change in the load is used. In the third scenario, the load is replaced by a laptop computer. Results show a close agreement between the voltage and the power responses of the proposed model and the actual PEM FC. Copyright © 2009 John Wiley & Sons, Ltd.     

An educational software package for Thyristor Switched Reactive Power Compensators using Matlab/Simulink

In this paper, an educational software package called TSCOM (Thyristor Switched Reactive Power Compensators) has been developed. The TSCOM software package contains simulation models of Thyristor Switched Capacitor (TSC) and Thyristor Switched Reactor (TSR)-based Static VAr Compensator (SVC) which are two of the shunt Flexible AC Transmission Systems (FACTS) devices. The design and simulations of TSC and TSR-based SVC are proposed using the Matlab/Simulink 7.04® and SimPowerSystems. The TSC and TSR-based SVC devices are demonstrated at two bus, three bus, infinite-bus, single-phase, three-phase, static load, dynamic load and stair-case load conditions. The effects of TSC and TSR-based SVC devices on load voltage are also analyzed. Student feedback indicates that this package is user-friendly and considerably effective for students and researchers to study theory of switched compensators, the reactive power control and voltage regulation. The proposed package will help to design the practical prototypes for students and researchers.     

Use of tuffs from central Turkey as admixture in pozzolanic cements: Assessment of their petrographical properties

Tuffs from Galatean Volcanic Province were studied for their use as admixtures in pozzolanic cements. The effects of petrographical properties on the pozzolanic activity of mortar specimens were investigated by optical microscopy, X-ray powder diffraction (XRD), scanning electron microscope equipped with an energy dispersive X-ray system (SEM-EDX), and chemical analysis. The chemical compositions of tuffs conform well to the requirements of ASTM C 618 and the Turkish Standard TS 25, and SiO₂+Al₂O₃+total Fe₂O₃ exceeds 70%. Pozzolanic activities were determined according to their 7th day flexural and compressive strengths and vary between 1.7 and 3.0 MPa and 7.4 and 16.0 MPa, respectively. The mechanical strength of mortars is affected by alteration of tuffs used in the mixture. Clay minerals and zeolites form by the alteration of volcanic glass, which is the most reactive phase and has a reducing effect on mechanical strength. The alteration also causes the enrichment of tuffs with respect to K₂O+Na₂O. The methods used provided rapid evaluation of tuffs as potential admixtures in cements.     

Synthesis and characterization of lithium calcium phosphate ceramics

The crystal structure, thermal, dielectrical, alternating current conductivity and microstructure properties of lithium calcium phosphate ceramics synthesized by the sol–gel method were investigated. The average crystallite size, crystallinity, activation energy and enthalpy of crystallization of Ca₁₀Li(PO₄)₇ ceramics were determined. The X-ray diffraction (XRD) results indicated that the apatitic structure belonging to HAp was transformed fully to Ca₁₀Li(PO₄)₇ phase with the addition of Li. The Avrami exponents of the samples suggest that the crystallization mechanism is based on the surface nucleation and one-dimensional growth. It was found that the alternating current conductivity mechanism of the ceramics is controlled by the hopping motion involving a translational motion with a sudden hopping. The dielectric constant of the samples shows a small increase with increasing amount of Li.     

Operation of TCSU with Internal Flux-Conserving Rings

The Translation, Confinement, and Sustainment Upgrade (TCSU) device is a facility to form and sustain a field-reversed configuration (FRC) in quasi-steady state using rotating magnetic fields (RMF). Recent campaigns include Ti gettering, the installation of a set of internal flux rings, and RMF frequency scans. The Ti gettering campaign was successful, reduced impurities, and reduced deuterium recycling from the walls allowing density control and hotter FRCs [J.A. Grossnickle et al., Phys. Plasmas 17, 032506 (2010)]. Internal flux rings have been installed to provide a uniform flux surface and minimize plasma-wall contact. Results from the internal flux ring operation and an additional Ti gettering campaign are reported. RMF frequencies of 123 kHz and 170 kHz have been investigated and initial results are reported.     

Section modulus of corner joints in furniture frames as engineering design criteria for their efficient construction

Since joints are often the weakest points in furniture construction a detailed analysis of the factors influencing their load bearing capacity and its effectiveness in utilizing the full strength of the wood is reported here.