bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser hole sealing of commercially pure grade 1 titanium
Authors: Huang Y. D. , Pequegnat A. , Khan M. I. , Feng J. C. , Zhou Y.
Published: June 2012

Hermetically sealed Ti capsules filled with electrolyte solutions are required in many medical device applications. The laser hole sealing process is well suited for this type of application. There is, however, a lack of understanding of the laser hole sealing mechanism, especially in the presence of an electrolyte medium. In this study, the mechanism of the laser hole sealing process was investigated by characterizing the surface morphology and cross-sections of welds made both with and without electrolyte. It was shown that the laser sealing mechanism transitions from (i) no sealing due to insufficient energy; (ii) the coalescence of the weld pool and the onset of sealing; (iii) increasing penetration depth up to full penetration; and (iv) laser ablation and drilling. Laser hole sealing in the presence of electrolyte decreases the size of the process window for suitable laser energies and affects the microstructure of the sealed hole.
Evaluation of Anaplasma phagocytophilum infection in experimentally inoculated sheep and determination of Anaplasma spp seroprevalence in 8 free-ranging sheep flocks in California and Oregon
Authors: Gorman Jennifer K. , Hoar Bruce R. , Nieto Nathan C. , Foley Janet E.
Published: June 2012

Objective—To evaluate disease progression in sheep experimentally inoculated with Anaplasma phagocytophilum and determine the Anaplasma spp seroprevalence in sheep in free-ranging flocks in the Sierra Nevada foothills and Oregon Coast Range.

Animals—10 mature ewes seronegative for Anaplasma spp and 251 sheep from 8 flocks.

Procedures—10 ewes received 1 of 3 treatments: A phagocytophilum Webster strain (n = 4), A phagocytophilum MRK strain (4), or human promyelocytic leukemia cells (control treatment [2]). Sheep were monitored for signs of clinical disease, and blood samples were obtained for serologic and PCR assay evaluation intermittently for 48 days. From a subsample of sheep from each of 8 free-ranging flocks, blood samples were obtained to determine Anaplasma spp seroprevalence.

Results—Sheep inoculated with A phagocytophilum developed subclinical or mild disease, whereas sheep inoculated with the control treatment did not develop any signs of disease. Only 2 ewes seroconverted; both had received the MRK strain. Anaplasma-specific DNA was detected in blood samples from 1 sheep in the Webster strain–inoculated group and 3 sheep in the MRK strain–inoculated group. Sheep seropositive for Anaplasma spp were detected in 5 of 8 flocks, and flocks in the Sierra Nevada foothills had higher within-flock seroprevalence (22%) than did flocks in the Oregon Coast Range (6.4%).

Conclusions and Clinical Relevance—Infection with A phagocytophilum in mature sheep generally resulted in subclinical disease. Higher Anaplasma spp seroprevalence in sheep in the Sierra Nevada foothills corresponded to the geographic distribution of anaplasmosis reported for dogs, horses, and humans.
Optimization of Satellite Combination in Kinematic Positioning Mode with the Aid of Genetic Algorithm
Authors: Srinuandee Panithan , Satirapod Chalermchon , Ogaja Clement , Lee Hung-Kyu
Published: June 2012

Optimization of Satellite Combination in Kinematic Positioning Mode with the Aid of Genetic Algorithm

The basis of high precision relative positioning is the use of carrier phase measurements. Data differencing techniques are one of the keys to achieving high precision positioning results as they can significantly reduce a variety of errors or biases in the observations and models. Since GPS observations are usually contaminated by many errors such as the atmospheric biases, the receiver clock bias, the satellite clock bias, and so on, it is impossible to model all systematic errors in the functional model. Although the data differencing techniques are widely used for constructing the functional model, some un-modeled systematic biases still remain in the GPS observations following such differencing. Another key to achieving high precision positioning results is to fix the initial carrier phase ambiguities to their theoretical integer values. To obtain a high percentage of successful ambiguity-fixed rates, noisy GPS satellites have to be identified and removed from the data processing step. This paper introduces a new method using genetic algorithm (GA) to optimize the best combination of GPS satellites which yields the highest number of successful ambiguity-fixed solutions in kinematic positioning mode. The results indicate that the use of GA can produce higher number of ambiguity-fixed solutions than the standard data processing technique.
Sensitivity of Lageos Orbits to Global Gravity Field Models
Authors: Sośnica K. , Thaller D. , Jäggi A. , Dach R. , Beutler G.
Published: June 2012

Sensitivity of Lageos Orbits to Global Gravity Field Models

Precise orbit determination is an essential task when analyzing SLR data. The quality of the satellite orbits strongly depends on the models used for dynamic orbit determination. The global gravity field model used is one of the crucial elements, which has a significant influence on the satellite orbit and its accuracy. We study the impact of different gravity field models on the determination of the LAGEOS-1 and -2 orbits for data of the year 2008. Eleven gravity field models are compared, namely JGM3 and EGM96 based mainly on SLR, terrestrial and altimetry data, AIUB-CHAMP03S based uniquely on GPS-measurements made by CHAMP, AIUB-GRACE03S, ITG-GRACE2010 based on GRACE data, and the combined gravity field models based on different measurement techniques, such as EGM2008, EIGEN-GL04C, EIGEN51C, GOCO02S, GO-CONS-2-DIR-R2, AIUB-SST. The gravity field models are validated using the RMS of the observation residuals of 7-day LAGEOS solutions. The study reveals that GRACE-based models have the smallest RMS values (i.e., about 7.15 mm), despite the fact that no SLR data were used to determine them. The coefficient C20is not always well estimated in GRACE-only models. There is a significant improvement of the gravity field models based on CHAMP, GRACE and GOCE w.r.t. models of the pre-CHAMP era. The LAGEOS orbits are particularly sensitive to the long wavelength part of the gravity fields. Differences of the estimated orbits due to different gravity field models are noticeable up to degree and order of about 30. The RMS of residuals improves from about 40 mm for degree 8, to about 7 mm for the solutions up to degrees 14 and higher. The quality of the predicted orbits is studied, as well.
Towards Understanding Collaborative Learning in the Social Media Environment
Authors: Kljajić Borštnar Mirjana
Published: June 2012

Towards Understanding Collaborative Learning in the Social Media Environment

‘Social media’, ‘Web 2.0’, ‘collaborative learning’ and user co-creation are just some of the terms that describe changes in the role of information and communication technology (ICT) in business, private life and society. The changing face of ICT has finally brought about the fulfilment of the term ‘Information Society’ and made an important impact on many fields of research, including collaborative learning. The effective use of ICT in support of group collaboration has been researched and discussed. The effectiveness was attributed to systematically organized and facilitated processes. Nevertheless, the results are not always better when group support systems (GSS) are used in comparison to face-to-face work. In contrast to the well-organized GSS-supported learning process, the social media environment is non-structured, rule-free and even chaotic. In this paper, we research the possibilities of eliciting group knowledge in the group-learning process in a social media environment. A total of 24 students assigned into three groups participated in the three-week long study. Their task was to solve a given research topic by solely using an unfamiliar social media environment and to present their findings after three weeks. Students were observed in their natural learning environment (school, home, the Flowr virtual environment), and their attitudes on collaborative work using social media tools were measured with a questionnaire at the end of the study. The results suggest that non-structured social media environment stimulates self-management of the group. Some insights into trust, motivation and conflicts in the collaborative problem solving are discussed.
Virtual Laboratory in Chemistry - Experimental Study of Understanding, Reproduction and Application of Acquired Knowledge of Subject's Chemical Content
Authors: Herga Nataša , Dinevski Dejan
Published: June 2012

Virtual Laboratory in Chemistry - Experimental Study of Understanding, Reproduction and Application of Acquired Knowledge of Subject's Chemical Content

Traditional teaching does not often allow very active involvement of pupils in class. In chemistry and natural sciences in general experimental and laboratory work is one of the most effective methods for acquiring knowledge. Experimental work can also be exercised using virtual world. Virtual laboratory offers some important advantages. Understanding chemistry involves the ability of cognitive comprehension on three levels: the macroscopic level, the symbolic level and the level of particles where the virtual laboratory can be an effective tool. On this basis a didactic experiment was performed in order to verify the effectiveness of virtual laboratory from pupils' knowledge point of view. The experiment involved seventh grade pupils (N = 38). Furthermore, we tried to answer the question whether the learning results of pupils, according to the experimental design of classes using a virtual laboratory, are better than results gained through teaching classical science classes without visualization tools. The research of the didactic experiment carried out on a relatively small, pilot sample of pupils has shown that acquiring knowledge is more effective when using the virtual laboratory instead of classical teaching (in the case when classical approach does not include visualization elements crucial for learning and understanding chemistry).
Solving Complex Problems with Help of Experiential Learning
Authors: Bernik Mojca , Žnidaršič Jasmina
Published: June 2012

Solving Complex Problems with Help of Experiential Learning

This paper presents the impact of experiential learning on solving complex problems. Analyzed are methods and techniques of experiential learning as an active form of learning. Presented are the results of research in which we examine whether the systematic approach of problem solving differs between the genders, if the perception of experience as a source of knowledge depends on the level of education, and examine a correlation between searching of all possible ways for successful problems solving and perception of experience as a source of knowledge.
Using the 3D Virtual Environments for Teaching: Report from the Field
Authors: Pivec Maja
Published: June 2012

Using the 3D Virtual Environments for Teaching: Report from the Field

Virtual worlds represent a powerful media for instruction, offering a wide scope of tools for social interaction and innovation in learning that encourages student participation. Supported by the AVATAR course, teachers were able to productively create teaching and learning environments that support the needs of learners of diverse linguistic, cultural and economic backgrounds, all within a safe virtual environment. This paper outlines the AVATAR course structure, delivery, experiences, and post course reflections on teaching within a 3D virtual world.
Trends in ICT and Multimedia Supported Education
Authors: Papić Marko , Bešter Janez
Published: June 2012

Trends in ICT and Multimedia Supported Education

The formal educational system is facing different problems regarding adaptation towards the needs of a modern knowledge society. In the article, two important and comprehensive challenges to today's formal educational system are discussed and commented upon. The first problem is the incoherence between the needs of the labor market and formal education system outcomes in terms of graduated students. Another problem is the distancing between the prevailing traditional pedagogical methods within formal educational institutions and the ways in which students acquire information and knowledge outside of the schools as they are becoming less and less interested in traditional lectures. It is argued that specific information and communication system technologies (ICT) supported mechanisms, such as social learning and virtual communities may address these challenges. Theories of communities and social learning that may be useful for implementation in the education system are explained and practical implementation is proposed.
The Conceptual Learning of Physics in Slovenian Secondary Schools
Authors: Ülen Simon , Gerlič Ivan
Published: June 2012

The Conceptual Learning of Physics in Slovenian Secondary Schools

In the last decade, educational researchers have been intensively searching for new, innovative teaching approaches. Information and Communication Technology (ICT) has a great didactic potential and project COLOS (Conceptual Learning of Science) encourages the use of ICT in the contemporary educational process. In this paper we present the conceptual learning of Physics. With experimental research we investigated the effectiveness of such learning in Slovenian secondary school. Two groups of third-year students who were enrolled in an introductory Physics course participated in the study. In the experimental group students were taught through the conceptual learning and in the control group a traditional expository instruction was used. We examined the knowledge of students after carrying out lessons specifically on the topic of Electricity. Five thinking processes were assessed - Knowledge (Recall), Analysis, Comparison, Inference and Evaluation. We found that the conceptual learning was more effective than the traditional instruction.
The Influence of Roughness on the Discharge Coefficient of a Broad-Crested Weir
Authors: Pařílková Jana , Říha Jaromír , Zachoval Zbyněk
Published: June 2012

The Influence of Roughness on the Discharge Coefficient of a Broad-Crested Weir

The use of environmentally-friendly materials in hydraulic engineering (e.g. the stone lining of weirs at levees) calls for the more accurate estimation of the discharge coefficient for broad-crested weirs with a rough crest surface. However, in the available literature sources the discharge coefficient of broad-crested weirs is usually expressed for a smooth crest. The authors of this paper have summarized the theoretical knowledge related to the effect of weir crest surface roughness on the discharge coefficient. The method of determination of the head-discharge relation for broad-crested weirs with a rough crest surface is proposed based on known discharge coefficient values for smooth surfaces and on the roughness parameters of the weir. For selected scenarios the theoretical results were compared with experimental research carried out at the Laboratory of Water Management Research, Faculty of Civil Engineering (FCE), Brno University of Technology (BUT).
Flow Structure of Coarse-Grained Slurry in A Horizontal Pipe
Authors: Vlasak Pavel , Kysela Bohus , Chara Zdenek
Published: June 2012

Flow Structure of Coarse-Grained Slurry in A Horizontal Pipe

The flow behaviour of coarse-grained slurry depends on particle size, shape, density and concentration, and on the density and rheological properties of the carrier liquid. The present paper describes the results of an experimental investigation and flow visualisation of model coarse-grained particle-water mixtures in a closed pipe loop with smooth stainless steel pipes of inner diameter 36 mm. Glass balls and washed graded pebble gravel of mean diameter d50= 6 mm were used as model coarse-grained material. The effect of slurry velocity and particle concentration on the slurry flow behaviour and pressure drop in the turbulent regime was evaluated. Particle distribution in the pipe cross-section and motion of particles along the pipe invert, particle saltation and particle conveying in the carrier liquid were investigated in a transparent pipe viewing section and motion of individual particles was described. Velocity profiles of the carrier liquid and conveyed particles were determined.
Hydrodynamic Investigation and Numerical Simulation of Intermittent and Ephemeral Flows in Semi-Arid Regions: Wadi Mekerra, Algeria
Authors: Korichi Khaled , Hazzab Abdelkrim
Published: June 2012

Hydrodynamic Investigation and Numerical Simulation of Intermittent and Ephemeral Flows in Semi-Arid Regions: Wadi Mekerra, Algeria

Semi-arid regions are characterized by important infrequent rainfall. They often occur in early autumn and give rise to devastating floods. Flooding problems at Wadi Mekerra, located in the Sidi Bel Abbes town (Northwest Algeria), was traditionally the main concern of researchers and government officials. In this work, the magnitude of raging flood wave in the studied catchment and the principal causes are discussed. After this, we present the main hydromorphometric features and the results of numerical simulations of flood wave. This simulation is done by using finite volume shock capturing schemes. It concerns applying the first order Godunov scheme and the second order Monotonic Central scheme. The Manning roughness coefficient was used as a calibration parameter. The comparison of numerical results with observed data confirms more stability and accuracy of applied numerical schemes in rising limb phase than in the falling limb phase. These results provide information on flood forecasting and monitoring of changes in the magnitude of the flow in Wadi Mekerra.
Experimental measurements of shape memory alloys wires
Authors: Kłapyta Grzegorz , Kciuk Marek
Published: June 2012

Experimental measurements of shape memory alloys wires

Paper deals with examinations of properties of shape memory alloy actuators. Authors describe design of own laboratory stand for obtaining electro-thermo-mechanical characteristics of SMA wires (maximum length 900 mm). The stand allows for semi-automatic measurements of voltage and current (supplying the actuator), temperature of wire and its extension. Data acquisition and control signals are realized by PC computer. All elements of the measuring system are connected by GPIB network (IEEE 488.2 standard). Control program for static measurements was written in G language (LabVIEW environment). Temperature is measured using infrared camera Flir A325. Displacement measurement system contains optical sensor (converting piston movement into series of pulses), pulses counter, PWM signal generator (PWM signal fulfillment is proportional to number of pulses), lowpass filter and buffer conditioning external signal. For dynamic measurements data recording is performed using digital oscilloscope Tektronix MSO 2024 equipped with four separated channels and digital filter. Wide range of examinations of several SMA wires allowed for drawing its exploitative characteristic helpful for practical use. It shows length change of actuator as a function of mechanical load (Fig. 10). Finally some example static as well as dynamic characteristics are presented and short discussion is carried out.
Application of a PSO algorithm for identification of the parameters of Jiles-Atherton hysteresis model
Authors: Knypiński Łukasz , Nowak Lech , Sujka Piotr , Radziuk Kazimierz
Published: June 2012

Application of a PSO algorithm for identification of the parameters of Jiles-Atherton hysteresis model

In the paper an algorithm and computer code for the identification of the hysteresis parameters of the Jiles-Atherton model have been presented. For the identification the particle swarm optimization method (PSO) has been applied. In the optimization procedure five design variables has been assumed. The computer code has been elaborated using Delphi environment. Three types of material have been examined. The results of optimization have been compared to experimental ones. Selected results of the calculation for different material are presented and discussed.
Vector operation of one-cycle controlled matrix rectifier
Authors: Yang Xinghua , Jiang Jianguo , Yang Xijun
Published: June 2012

Vector operation of one-cycle controlled matrix rectifier

A novel vector operated one-cycle control matrix rectifier (OCC-MR) is proposed in this paper. Matrix rectifier (MR) is a generalized buck three-phase AC-DC converter with four-quadrant operation capability. MR can also be the front-stage circuit of AC-DC-AC equivalent structure of MC. One-cycle control (OCC) is a nonlinear control technique, which integrates modulation algorithm and control strategy. By applying OCC to current control loop, the OCC-MR achieves balance only in a switching cycle, and realizes unitary input power factor. Furthermore, vector operation of OCC results in minimum switching losses. In order to make up for the insufficiency of OCC on load disturbance suppression, a PID controller is added onto output voltage control to improve load regulation. The OCC-MR features great simplicity, fast dynamic response and good immunity on input disturbance. On the basis of theoretical analysis, a systematic simulation of OCC-MR is implemented by means of Matlab/Simulink. Both static state performance and dynamic state performance of OCC-MR are discussed deeply. The simulation results have proved theoretical analysis of the vector operation of OCC-MR, and the control effects are satisfactory.
Observer-based fault diagnosis and field oriented fault tolerant control of induction motor with stator inter-turn fault
Authors: Toumi Djilali , Boucherit Mohamed , Tadjine Mohamed
Published: June 2012

Observer-based fault diagnosis and field oriented fault tolerant control of induction motor with stator inter-turn fault

This paper describes a fault-tolerant controller (FTC) of induction motor (IM) with inter-turn short circuit in stator phase winding. The fault-tolerant controller is based on the indirect rotor field oriented control (IRFOC) and an observer to estimate the motor states, the amount of turns involved in short circuit and the current in the short circuit. The proposed fault controller switches between the control of the two components of measured stator current in the synchronously rotating reference frame and the control of the two components of estimated current in the case of faulty condition when the estimated current in the short circuit is not destructive of motor winding. This technique is used to eliminate the speed and the rotor flux harmonics and to assure the decoupling between the rotor flux and torque controls. The results of the simulation for controlling the speed and rotor flux of the IM demonstrate the applicability of the proposed FTC.
The applications of fixed-point theorem in optimisation problems
Authors: Chwastek Krzysztof
Published: June 2012

The applications of fixed-point theorem in optimisation problems

The fixed-point theorem is widely used in different engineering applications. The present paper focuses on its applications in optimisation. A Matlab toolbox, which implements the branch-and-bound optimisation method based on the fixed-point theorem, is used for solving different real-life test problems, including estimation of model parameters for the Jiles-Atherton model.
Influence of constructional turbo-generator end region design on end winding inductances
Authors: Freese Michael , Kulig Stefan
Published: June 2012

Influence of constructional turbo-generator end region design on end winding inductances

The paper introduces a comprehensive investigation in end winding inductances of large two-pole turbo-generators. With the aid of an analytic-numeric approach, where Neumann's formula is applied, the influence of geometric characteristics of double-layer stator end windings with involute shape is analysed. This parameter study results in approximation formulas for the stator self and mutual inductances at strand level as well as for the common used end winding leakage inductance. In order to consider field affecting components as pressure plate, flux shield, rotor shaft and rotor retaining ring, finite elements models for two machines (250 MVA and 1150 MVA) are created and computed. The results are integrated in the developed approximation formulas. Finally the simulation results of machine 1 are compared to the data of two different measurements. All approaches introduced in this paper show good correlation. The high speed of the analytic-numeric calculation is combined with the accuracy and opportunity to consider field affecting components within the extensive finite element computation successfully.
Conformal mapping approach for permanent magnet synchronous machines: on the modeling of saturation
Authors: Hafner Martin , Franck David , Hameyer Kay
Published: June 2012

Conformal mapping approach for permanent magnet synchronous machines: on the modeling of saturation

In the electromagnetic field simulation of modern servo drives, the computation of higher time and space harmonics is essential to predict torque pulsations, radial forces, ripple torques and cogging torque. Field computation by conformal mapping (CM) techniques is a time-effective method to compute the radial and tangential field components. In the standard CM approach, computational results of cogging torque simulations as well as overload operations observe deviations to nonlinear finite element (FE) simulations due to the neglection of slot leakage and saturation effects. This paper presents an extension of the classical CM. Additional CM parameters are computed from single finite element computations so as to consider both effects listed above in the model over a wide operation range of the electrical drive. The proposed approach is applied to a surface permanent magnet synchronous machine (SM-PMSM), and compared to numerical results obtained by finite element analysis (FEA). An accuracy similar to that of FE simulations is obtained with however the low computation time that is characteristic for analytical models.
An improved calculation method of inductance and capacitances in π1 circuits for resonant power amplifiers
Authors: Modzelewski Juliusz , Kulma Katarzyna
Published: June 2012

An improved calculation method of inductance and capacitances in π1 circuits for resonant power amplifiers

In the paper an improved method of calculation of the inductance and capacitances in the π1 circuit for Class A, AB, B, and C resonant power amplifiers is presented. This method is based on an assumption that the quality factor of the inductor is finite and the capacitors are lossless. The input parameters for calculations are the amplifier load resistance, the transistor load resistance, the quality factor of the inductor, the loaded quality factor of the designed circuit, and the operating frequency. The presented method allows reducing the required regulation range of π1 circuits elements in built resonant amplifiers as compared to the traditional calculation methods assuming lossless capacitors and inductor. This advantage is important, in particular, for long- and medium-wave transistor power amplifiers, where capacitances in π1 circuits are high comparing to typical trimming capacitors.
Application of UPFC for enhancement of voltage profile and minimization of losses using Fast Voltage Stability Index (FVSI)
Authors: Kumar M. , Renuga P.
Published: June 2012

Application of UPFC for enhancement of voltage profile and minimization of losses using Fast Voltage Stability Index (FVSI)

Transmission line loss minimization in a power system is an important research issue and it can be achieved by means of reactive power compensation. The unscheduled increment of load in a power system has driven the system to experience stressed conditions. This phenomenon has also led to voltage profile depreciation below the acceptable secure limit. The significance and use of Flexible AC Transmission System (FACTS) devices and capacitor placement is in order to alleviate the voltage profile decay problem. The optimal value of compensating devices requires proper optimization technique, able to search the optimal solution with less computational burden. This paper presents a technique to provide simultaneous or individual controls of basic system parameter like transmission voltage, impedance and phase angle, thereby controlling the transmitted power using Unified Power Flow Controller (UPFC) based on Bacterial Foraging (BF) algorithm. Voltage stability level of the system is defined on the Fast Voltage Stability Index (FVSI) of the lines. The IEEE 14-bus system is used as the test system to demonstrate the applicability and efficiency of the proposed system. The test result showed that the location of UPFC improves the voltage profile and also minimize the real power loss.
Analysis of a single-phase capacitor induction motor operating at two power line frequencies
Authors: Leicht Aleksander , Makowski Krzysztof
Published: June 2012

Analysis of a single-phase capacitor induction motor operating at two power line frequencies

The paper presents a modelling mathematical tool for prediction of dynamic and steady-states operation of the single-phase capacitor induction motor for different values of the capacitor capacitance and different frequency of voltage supply at no-load and rated load conditions. Developed mathematical model of the capacitor induction motor was implemented for calculation using Matlab/Simulink software. Presented simulation results may be utilized to achieve better starting quality of single-phase capacitor induction motors.
Determination of best rotor length in solid-rotor induction motor with axial slitting
Authors: Jagiela Mariusz , Garbiec Tomasz
Published: June 2012

Determination of best rotor length in solid-rotor induction motor with axial slitting

The efficiency of the solid-rotor induction machines depends on axial length of rotor (including the end-regions). Determination of the best axial length is problematic because of current density distribution in the end-regions and also because of absence of dedicated methods and models. This work proposes a method that circumvents this difficulty. It is based on the numerical determination of a dimensionless rotor-end factor using a combination of three- and two-dimensional finite element models restricted to the motor rotor. Such the end factor can be used in both analytical and numerical model of the machine in order to determine the typical performance characteristics. In this work, using this method, we determined an optimal length of the slitted solid rotor of a motor operating at 12 000 rpm, that maximizes the motor efficiency. The results of computations and measurements, carried out on the laboratory test-stand, are presented.
Study of delta/polygon-connected transformer-based 36-pulse ac-dc converter for power quality improvement
Authors: Abdollahi Rohollah
Published: June 2012

Study of delta/polygon-connected transformer-based 36-pulse ac-dc converter for power quality improvement

Design of a delta/polygon-connected autotransformer based 36-pulse ac-dc converter is presented in this paper. The 36-pulse topology is obtained via two paralleled eighteen-pulse ac-dc converters each of them consisting of a nine-phase (nine-leg) diode bridge rectifier. For independent operation of paralleled diode-bridge rectifiers, two interphase transformers (IPT) is designed and implemented. A transformer is designed to supply the rectifier. The design procedure of magnetics is in a way such that makes it suitable for retrofit applications where a six-pulse diode bridge rectifier is being utilized. The proposed structure has been implemented and simulated using Matlab/Simulink software under different load conditions. Simulation results confirmed the significant improvement of the power quality indices (consistent with the IEEE-519 standard requirements) at the point of common coupling. Furthermore, near unity power factor is obtained for a wide range of DTCIMD operation. A comparison is made between 6-pulse and proposed converters from view point of power quality indices. Results show that input current total harmonic distortion (THD) is less than 4% for the proposed topology at variable loads.
Host range and host choice of Cuscuta species in Hungary
Authors: Baráth Kornél , Csiky János
Published: June 2012

- Extensive field studies were carried out in Hungary to get a picture of the host range and host choice of the Cuscuta species under natural conditions.We examined both parasitised and unparasitised plant species and found some aspects in which they are different. Compiling the host spectra of the various Cuscuta species based on herbaria, literature and our own observations, we can say that dodders infest at least 26% of the vascular flora of the country. In our study, the Hungarian Cuscuta species parasitised all plants that had a coverage of more than 25% in the sampling sites.We prepared a list of the most frequent host species for the parasites and revealed the importance of exclusive hosts. The results suggest that the habitat differences of the Cuscuta species can be responsible for the different host ranges. Furthermore, it was found that the reason why dodders parasitise plants from various life-forms in different proportions is not (only) the active host choice, but the characteristic features of the habitats.
Squat - Rules of Performing and Most Common Mistakes
Authors: Czaprowski Dariusz , Biernat Ryszard , Kędra Agnieszka
Published: June 2012

Squat - Rules of Performing and Most Common Mistakes

The squat is an exercise which is commonly applied in sport, recreation and while performing numerous everyday activities [1, 2, 3]. The improper performance of the squat leads to the shaping of an improper movement pattern.

In this work the methodology of teaching the squat, which has to be learnt to constitute a significant element in the prophylaxis of the musculoskeletal system overloads, is described.
Strength in Young Italian Students: Results from Eurofit Test and Comparison Among European Data
Authors: Lovecchio Nicola , Casolo Francesco , Invernizzi Pietro , Eid Luca
Published: June 2012

Strength in Young Italian Students: Results from Eurofit Test and Comparison Among European Data

Introduction.
The health-related benefits of physical activity are well known. Participation in a physical activity could improve social well-being, as well as physical and mental health, among children and adolescents.
Material and methods.
Thus, during Physical Education lessons, over 1500 students were tested with the Bent Arm Hung and the Standing Broad Jump test; according to the instructions given by Eurofit battery. All phases of the test had been run by teachers that collected data relative to lower limb power and upper limbs isometric endurance strength.
Results.
Females jumped 150 cm (on average) while in Bent Arm Hung scored scantly results. The variability was high in both test. Males jumped over their own height with a variation smaller than females'. About isometric endurance strength the best group was the 16 years (male).
Conclusion.
These two tests showed in both genders a similar pattern to that of other young Europeans but future research are necessary to separate the correlation about country, rural area of origin and socioeconomic status. It may be concluded that the level of physical activity (and the possibility to play it) was a decisive factor on the level of performance.
Mood Changes in Physically Active Men in Situations of Imagined Discontinuation of Physical Exercises as an Indication of the Risk of Addiction to Physical Exercises
Authors: Guszkowska Monika , Rudnicki Paweł
Published: June 2012

Mood Changes in Physically Active Men in Situations of Imagined Discontinuation of Physical Exercises as an Indication of the Risk of Addiction to Physical Exercises

Introduction.
The phenomenon of addiction to exercise is one of the risks of systematically undertaken recreational physical activity. It is more common in men, especially those undertaking intense aerobic workout. The diagnostic criteria include the so called withdrawal symptoms expressed by deterioration of mood in the situation of discontinuation of exercise. The aim of this study was to determine mood changes in regularly exercising men in the situation of imagined discontinuation of exercise compared to the neutral situation, and their relation to the length of involvement in sports, the frequency and duration of exercise and the risk of addiction to exercise.
Material and methods.
The study involved 45 men aged 20-33 years who practice recreational jogging, combat sports, and exercising at the gym. Standard scales were used to test the mood: Profile of Mood States (POMS) and the Mood Adjective Check List (UMACL), measuring the emotional states in neutral situation and the imaginary discontinuation of exercise and the scale to assess the risk of dependence on exercise developed for the study.
Results.
The results show a significant deterioration of mood in the situation imagined discontinuation of exercise, as compared to the neutral situation. Its magnitude grows along with the length of the men's involvement in sports, but there were no significant associations with the frequency or duration of exercise. The risk of addiction to exercise is positively correlated to the mood deterioration and the length of involvement in sports. Young men who systematically exercise regularly expect a significant deterioration in their mood in a situation of discontinuation of exercise, which suggests that there is a risk of addiction to physical exercise.
Special Fitness Level and Sports Achievements of 15-16-Year-Old Pole Vaulters
Authors: Kochanowicz Kazimierz , Klimczyk Mariusz
Published: June 2012

Special Fitness Level and Sports Achievements of 15-16-Year-Old Pole Vaulters

Introduction.
Control of specific performance indicators makes it possible to obtain the necessary information for determining dominant characteristics to program sports training taking into account the stage of advancement of sports and athletic performance prediction. Therefore, the aim of the study was to determine the most relevant specific performance indicators in athletes aged 15-16 years practicing the pole vault.
Material and methods.
The study involved 10 athletes at the first stage at the age of 15 and at the second at the age of 16 practicing pole vault, in the following clubs S.L. WKS, "Zawisza" Bydgoszcz, "Gwardia" Piła, "Śląsk" Wrocław. The study was conducted under training conditions and athletic competition in 2008-2009. The study utilized the method of pedagogical observation and case study. The research tools used involved evaluation of physical fitness and athletic fitness and sporting achievements, conducted during the competition period. To analyze the research results basic statistical methods were used.
Conclusions.
Special fitness growth dynamics indicators were determined, and analysis of the correlation of these indicators with the sporting achievement was performed. The highest correlation with the pole vault of 0.92 was recorded in an attempt to "fly" over the bar with rollover backwards while doing a handstand. A similar correlation of results was also shown by the special fitness analysis of three competitors with the best results in pole vault. However, in trials of running speed and muscle strength, each of the tested pole vaulters was characterized by an individual development profile.
Variants of Development of Sports Career of 11-Year-Old Female Swimmers
Authors: Bielec Grzegorz
Published: June 2012

Variants of Development of Sports Career of 11-Year-Old Female Swimmers

Introduction.
The development of a sporting career takes a course within a phased manner, the various stages are characterized by different goals and tasks. In competitive swimming there are many cases of athletes who achieved high sporting results in the category of children and youths and who soon after abandoned their interest in training. The aim of this study was to find the association between the sports achievements of 11-year-old girls competing in the 200 m backstroke events and their sports level in the subsequent years of their career.
Material and methods.
The results of the sporting careers of girls who ranked from 1st to 20th in the 200 m backstroke event in the Polish Correspondence Championships for 10 and 11-Year-Old Children in 2003 were presented. Their positions taken in subsequent editions of the summer Polish championship till 2009 were the criterion of their career development. An analysis of documents was used as a scientific method. The basis for the analysis were post-competition protocols listed on the official website of the Polish Swimming Federation.
Results.
Only 30% of the examined athletes took part in all main events intended for their age. Less than half of them participated in the Polish 17-18-Year-Old Junior Championships organized within the Nationwide Juvenile Olympics. 40% of the girls from the studied group ended their careers before the age of 15. Four basic variants of development of a sporting career were observed in the group.
Conclusions.
After analyzing the athletes' careers it can be stated that a high position in the national ranking of 11-year-olds does not guarantee significant sporting achievements in later years. In the studied group of girls the stroke and distance specialization had changed in most cases (80%).
Emotional Intelligence and the Sense of Efficiency of Coaching and Instructing in Wrestling
Authors: Rutkowska Katarzyna , Gierczuk Dariusz
Published: June 2012

Emotional Intelligence and the Sense of Efficiency of Coaching and Instructing in Wrestling

Introduction.
The aim of this study was to diagnose the level of emotional intelligence and sense of efficiency among the occupational group of coaches and instructors in wrestling.
Material and methods.
The study involved 27 participants of a training course for coaches and instructors in training (25 men and 2 women). The basic methods of research involved the Emotional Intelligence Questionnaire INTE and the GSES scale for measurement of the sense of efficacy. Their use allowed us to diagnose the average level of emotional intelligence and the sense of self-efficacy.
Results.
Coaches and instructors are characterised by average level of emotional intelligence and the sense of self-efficacy. First class coaches are characterized by significantly higher levels of emotional intelligence, and the belonging to the group of trainers has no influence on the sense of efficacy.
Conclusions.
The results of the study can provide guidance to create/modify training programs for sports coaches. Developing mental toughness and improving emotional intelligence should occupy a special place in the training process wrestlers.
Own Business Enterprise in the Professional Plans of Tourism and Recreation Students
Authors: Skiert Małgorzata , Buchta Krystyna
Published: June 2012

Own Business Enterprise in the Professional Plans of Tourism and Recreation Students

Introduction.
This study deals with the issue of career plans of tourism and recreation students. The aim of this study was to determine the degree of willingness of the respondents to take on business proprietorship, and to identify determinants of their behaviour in this regard. The research focused on the preparation of students in the course of their education to take on business initiatives their own.
Material and methods.
The study was conducted in the 2010/2011 academic year, using the method of diagnostic poll and the auditorium survey technique. It included 167 first-year full time students majoring in Tourism and Recreation of the University of Physical Education in Warsaw (Faculty of Physical Education and Sport in Biała Podlaska).
Results.
The results of studies have showed that students express a great deal of interest in business proprietorship. They are primarily motivated by desire to maintain independence of decision-making, the need to develop their own interests and the expected high incomes. The main obstacle in this respect appears to be the lack of necessary funds to run own company. The assessed their professional business entrepreneurship skills relatively low, pointing to the lack of proper preparation in the course of the studies. Particularly low assessment was given to their skills regarding the raising funds necessary to start and run a business.
Sport-Tourism Interests in the Light of all the Interests of Physical Education Students in the Selected Academies in Poland
Authors: Brojek Anna , Bochenek Anna
Published: June 2012

Sport-Tourism Interests in the Light of all the Interests of Physical Education Students in the Selected Academies in Poland

Introduction.
Children's and youth's interests are of great importance in the view of pedagogical science. It is an element of a human's personality which makes people take action and for endeavours to achieve particular aims.
Material and methods.
The method applied in the research was the diagnostic survey based on a questionnaire. The questionnaire used in the research was the Springer's Interests Questionnaire adopted by Cekiera and an open question like ‘What are your interests?’. The survey was conducted in Academic Year 2008/2009 among 667 first-year physical education students of the first level of full-time studies in eight academies in Poland.
Results.
The conducted survey indicates that, among all the first-year physical education students' interests, there is a clear tendency for students to be interested in sport and tourism. The majority of respondents tends to be interested only in sport and tourism, they are defined as one-track mind students, and this can be proven through their deep and extensive knowledge in these subjects. The factors that significantly influence and differentiate the statistics of the survey were: sex, social background and place of residence. However, the type of school finished does not have an impact on the result of the survey since there is no connection between the finished school and interests.
Conclusion.
Owing to the fact that the majority of respondents definitely show a one-track mind interest in sport-tourism and care-education, it can be suggested that they tend to have the right qualities to be teachers of physical education.
A comparison of the activation energy of viscous flow for hen egg-white lysozyme obtained on the basis of different models of viscosity for glass-forming liquids
Authors: Monkos Karol
Published: June 2012

A comparison of the activation energy of viscous flow for hen egg-white lysozyme obtained on the basis of different models of viscosity for glass-forming liquids

The paper presents the results of viscosity determinations on aqueous solutions of hen egg-white lysozyme at a wide range of concentrations and at temperatures ranging from 5°C to 55°C. On the basis of these measurements and different models of viscosity for glass-forming liquids, the activation energy of viscous flow for solutions and the studied protein, at different temperatures, was calculated. The analysis of the results obtained shows that the activation energy monotonically decreases with increasing temperature both for solutions and the studied protein. The numerical values of the activation energy for lysozyme, calculated on the basis of discussed models, are very similar in the range of temperatures from 5°C to 35°C.