bluuebunny/crossref_metadata_2025_split huggingface dataset:
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, AlgeriaSemi-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 modelIn 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 inductancesThe 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 frequenciesThe 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 improvementDesign 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

Abstract
- 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.
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.
Interaction of metalloporphyrins with lipid bilayers, a calorimetric study
Authors: Pamin Katarzyna , Połtowicz Jan , Kiełkowicz Joanna , Hendrich Andrzej 
Published: June 2012

Interaction of metalloporphyrins with lipid bilayers, a calorimetric studyThe interaction of three metalloporphyrins, containing manganese, iron and cobalt atoms, with lipid bilayers composed of neutral (DPPC) or charged (DMPG) phospholipids were studied by means of scanning differential calorimetry. We found only minute effects exerted by studied compounds on DPPC, while phase transitions of charged DMPG were seriously affected by porphyrins. Analysis of experimental data revealed that due to the electrostatic interactions DMPG bilayers are perturbed not only in the polar head group region. Putative rearrangements of the polar heads packing affects also the acyl chain region of this lipid bilayer. Perturbation of DMPG polar heads induced by porphyrin in complex with manganese atoms is bigger than that induced by other porphyrins.
Antioxidant potentials of polyphenolic extracts from leaves of trees and fruit bushes
Authors: Cyboran Sylwia , Bonarska-Kujawa Dorota , Kapusta Ireneusz , Oszmiański Jan , Kleszczyńska Halina 
Published: June 2012

Antioxidant potentials of polyphenolic extracts from leaves of trees and fruit bushesThe aim of the work was to determine the antioxidant potential of extracts from leaves of strawberry, blackcurrant and apple in relation to lipids contained in the erythrocyte membrane. The studies performed have shown that the substances used protect membrane lipids against oxidation, clearly reducing the level of free radicals in erythrocyte ghosts suspension. The antioxidant activity of the substances studied follows the sequence: strawberry leaves > apple leaves > blackcurrant leaves. The results of the research on the antioxidant activity when confronted with the contents of polyphenols in the extracts indicates that the antioxidant potentials of the extracts depend both on the quantity and kind of individual polyphenols; in particular, on the kind and quantity of quercetin derivatives that constitute over 60 % of all the phenolic compounds. Moreover, the high antioxidant activity of the extracts may be also due to other, nonphenolic substances that occur in leaves. The extracts exhibit very good properties as free radical scavenges, and can thus be used as cheap, easily available, natural antioxidants in the industries where natural antioxidants in the form of fruit extracts have been used for long.
The effect of aclarubicin (acl) on human erythrocytes
Authors: Witczak Piotr , Marczak Agnieszka 
Published: June 2012

The effect of aclarubicin (acl) on human erythrocytesThe present study examines the influence of aclarubicin (ACL) on human red blood cells with a focus on the generation of reactive oxygen species (ROS). A statistically significant increase in ROS levels was observed for all the tested concentrations of aclarubicin (1-20 nM). The depletion of catalase activity and elevated metHb content were also observed. On the other hand, changes in reduced glutathione (GSH) and total glutathione concentrations were not statistically significant. The presented results confirm important role of ROS in ACL cytotoxic activity.