Showing papers by "Wrocław University of Technology published in 2010"
TL;DR: The paper discusses the possibilities which offer research on pollutants-biomass interactions, pointing out that the key to elaborate an efficient method working for the nature would be to understand the mechanisms governing the processes, parameters which influence both equilibrium and kinetics, through the observation of naturally occurring phenomena.
651 citations
12 Sep 2010
TL;DR: The results of this work makes next step towards defining formal methods of reuse defect prediction models by identifying groups of projects within which the same defect prediction model may be used.
Abstract: Background: This paper describes an analysis that was conducted on newly collected repository with 92 versions of 38 proprietary, open-source and academic projects. A preliminary study perfomed before showed the need for a further in-depth analysis in order to identify project clusters.Aims: The goal of this research is to perform clustering on software projects in order to identify groups of software projects with similar characteristic from the defect prediction point of view. One defect prediction model should work well for all projects that belong to such group. The existence of those groups was investigated with statistical tests and by comparing the mean value of prediction efficiency.Method: Hierarchical and k-means clustering, as well as Kohonen's neural network was used to find groups of similar projects. The obtained clusters were investigated with the discriminant analysis. For each of the identified group a statistical analysis has been conducted in order to distinguish whether this group really exists. Two defect prediction models were created for each of the identified groups. The first one was based on the projects that belong to a given group, and the second one - on all the projects. Then, both models were applied to all versions of projects from the investigated group. If the predictions from the model based on projects that belong to the identified group are significantly better than the all-projects model (the mean values were compared and statistical tests were used), we conclude that the group really exists.Results: Six different clusters were identified and the existence of two of them was statistically proven: 1) cluster proprietary B -- T=19, p=0.035, r=0.40; 2) cluster proprietary/open - t(17)=3.18, p=0.05, r=0.59. The obtained effect sizes (r) represent large effects according to Cohen's benchmark, which is a substantial finding.Conclusions: The two identified clusters were described and compared with results obtained by other researchers. The results of this work makes next step towards defining formal methods of reuse defect prediction models by identifying groups of projects within which the same defect prediction model may be used. Furthermore, a method of clustering was suggested and applied.
471 citations
TL;DR: The allowable range of motor-parameter changes is determined, which guarantees the stable operation of the sensorless field-oriented IM drive with this speed and flux estimator, and the stability of the whole drive system is guaranteed.
Abstract: This paper deals with an analysis of the vector-controlled induction-motor (IM) drive with a novel model reference adaptive system (MRAS)-type rotor speed estimator. A stability-analysis method of this novel MRAS estimator is shown. The influence of equivalent-circuit parameter changes of the IM on the pole placement of the estimator transfer function and the stability of the whole drive system are analyzed and tested. The influence of the adaptation-algorithm coefficients of the MRAS-estimator scheme is also tested. The allowable range of motor-parameter changes is determined, which guarantees the stable operation of the sensorless field-oriented IM drive with this speed and flux estimator. Dynamical performances of the vector-control system with the current-type MRAS estimator are tested in a laboratory setup.
387 citations
TL;DR: Oxidation with Chiral Oxaziridines 4309 1.2.1.
Abstract: 1.2.2. Davis Oxaziridines 4305 1.2.3. Metal Complexes in Enantioselective Oxidation 4305 1.3. New Applications 4307 1.3.1. Chiral Sulfinate Method 4307 1.3.2. Oxidation with Chiral Oxaziridines 4309 1.3.3. Oxidation Using Metal Complexes 4310 1.4. New Systems 4313 1.4.1. C-S Bond Formation 4314 1.4.2. Organic Oxidants 4315 1.4.3. Oxidations Catalyzed by Metal Complexes 4316 1.5. Diastereoselective Oxidations 4330 1.6. Heterogenized Systems 4332 1.7. Summary 4335 2. Biological Oxidations 4336 2.
368 citations
Book•
29 Apr 2010TL;DR: Boundary potential theory for Schr#x00F6 dinger operators based on fractional Laplacian is proposed in this article, where the potential theory of subordinate Brownian motion is applied to the potential potential theory.
Abstract: Boundary Potential Theory for Schr#x00F6 dinger Operators Based on Fractional Laplacian.- Nontangential Convergence for #x03B1 -harmonic Functions.- Eigenvalues and Eigenfunctions for Stable Processes.- Potential Theory of Subordinate Brownian Motion.
244 citations
TL;DR: A survey of state-of-the-art non-destructive diagnostic techniques of testing building structures and examples of their applications can be found in this article, where the authors focus on techniques suitable for: detecting defects invisible on the surface, estimating the depth of cracks, determining the dimensions of elements accessible from one side only and 2D and 3D imaging of reinforcement distribution in such elements.
201 citations
TL;DR: It is shown that torsional oscillations can be successfully suppressed in the proposed control structure, using only one basic feedback from the motor speed given by the proposed speed estimator.
Abstract: In this paper, the concept of a model reference adaptive control of a sensorless induction motor (IM) drive with elastic joint is proposed. An adaptive speed controller uses fuzzy neural network equipped with an additional option for online tuning of its chosen parameters. A sliding-mode neuro-fuzzy controller is used as the speed controller, whose connective weights are trained online according to the error between the estimated motor speed and the speed given by the reference model. The speed of the vector-controlled IM is estimated using the MRASCC rotor speed and a flux estimator. Such a control structure is proposed to damp torsional vibrations in a two-mass system in an effective way. It is shown that torsional oscillations can be successfully suppressed in the proposed control structure, using only one basic feedback from the motor speed given by the proposed speed estimator. Simulation results are verified by experimental tests over a wide range of motor speed and drive parameter changes.
201 citations
TL;DR: In this paper, the authors calibrate and test a range of MRS models in an attempt to find parsimonious specifications that not only address the main characteristics of electricity prices but are statistically sound as well.
180 citations
TL;DR: In this paper, the authors reviewed the extensive published literature on separation methods of boron removal from seawater and reported that this limit is rarely reached for conventional reverse osmosis desalination plants equipped with commercially available membranes.
178 citations
TL;DR: A review of the literature on solvent-impregnated resins can be found in this article, where the authors attempt to stabilize hybrid polymeric adsorbent material and various applications of SIRs.
Abstract: Interest in the development of solvent-impregnated resins (SIRs) and their applications for the separation of metal ions and organic compounds from water in the form of a hybrid polymeric adsorbent material has intensified over the past thirty years. SIRs are particulate adsorbers that possess a combination of the advantageous features of both liquid–liquid extraction and ion exchange and this renders them applicable to a wide range of potential liquid–solid separation and recovery processes. This paper reviews the extensive published literature on methods of synthesis of SIRs, attempts to stabilize hybrid solvent-impregnated resins and various applications of SIRs.
156 citations
TL;DR: In this paper, two models of gearboxes (a fixed-axis two-stage gearbox and a planetary gearbox) operating under varying load conditions are proposed, and an original transmission error function expressing changes in technical condition and load variation is presented.
Abstract: Fault detection and diagnosis in mechanical systems during their time-varying nonstationary operation is one of the most challenging issues. In the last two decades or so researches have noticed that machines work in nonstationary load/speed conditions during their normal operation. Diagnostic features for gearboxes were found to be load dependent. This was experimentally confirmed by a smearing effect in the spectrum. In order to better understand the involved phenomena and to ensure agreement between simulation and experimental results, two models of gearboxes (a fixed-axis two-stage gearbox and a planetary gearbox) operating under varying load conditions are proposed. The models are based on two mechanical systems used in the mining industry, i.e. the belt conveyor and the bucket wheel excavator. An original transmission error function expressing changes in technical condition and load variation is presented. Energy based parameters (the signal RMS value or the arithmetic sum of the amplitudes of spectral gearmesh components) are adopted as the diagnostic features. Simulation results show a strong correlation between load values, changes in condition and the diagnostic features. The findings are key to condition monitoring. Thanks to the use of the models one can better understand the phenomena identified through an analysis of vibration signals captured from real machines.
TL;DR: The fabrication and characterization of the first guiding chalcogenide As(2)S(3) microstructured optical fibers with a suspended core with a zero dispersion wavelength (ZDW) is reported.
Abstract: We report the fabrication and characterization of the first guiding chalcogenide As2S3 microstructured optical fibers (MOFs) with a suspended core. At 1.55 µm, the measured losses are approximately 0.7 dB/m or 0.35 dB/m according to the MOF core size. The fibers have been designed to present a zero dispersion wavelength (ZDW) around 2 µm. By pumping the fibers at 1.55 µm, strong spectral broadenings are obtained in both 1.8 and 45-m-long fibers by using a picosecond fiber laser.
TL;DR: Forster resonance energy transfer between nanoparticles of up-conversion lanthanide phosphor as donors and quantum dots as acceptors is demonstrated in this paper, where the green erbium upconversion emission at 540 nm is efficiently quenched by quantum dots (QDs) leading to color change of the mixture for different relative concentrations.
Abstract: Forster resonance energy transfer (FRET) between nanoparticles of up-conversion lanthanide phosphor as donors and quantum dots as acceptors is demonstrated. Fluoride (NaYF4) nanocrystals (ca. 30 nm size) codoped with the Er3+ and Yb3+ ions were synthesized with a high-pressure solvothermal microwave assisted technique and dispersed in organic solvent. Up-converted luminescence from the rare-earth ions doped into fluoride nanomatrix was achieved with optical pumping in NIR (976 nm) region. The green erbium upconversion emission at 540 nm is efficiently quenched by quantum dots (QDs) leading to color change of the mixture for different relative concentrations. Simultaneously, orange emission from quantum dots appears due to energy transfer from Er3+/Yb3+:NPs donors to QDs acceptors. The concomitant decrease of the average lifetime of donor emission at 540 nm (from ∼153 to ∼130 μs) indicates that the excitation of CdSe QDs occurs not only through reabsorption but also through Forster Resonance Energy Transfe...
TL;DR: Two birefringent microstructuring fibers are designed, manufactured and characterized that feature a 5-fold increase in polarimetric sensitivity to hydrostatic pressure compared to the earlier reported values for microstructured fibers.
Abstract: We designed, manufactured and characterized two birefringent microstructured fibers that feature a 5-fold increase in polarimetric sensitivity to hydrostatic pressure compared to the earlier reported values for microstructured fibers. We demonstrate a good agreement between the finite element simulations and the experimental values for the polarimetric sensitivity to pressure and to temperature. The sensitivity to hydrostatic pressure has a negative sign and exceeds −43 rad/MPa × m at 1.55 μm for both fibers. In combination with the very low sensitivity to temperature, this makes our fibers the candidates of choice for the development of microstructured fiber based hydrostatic pressure measurement systems.
TL;DR: The presented data indicates that waste composition strongly depends on the type of housing and its heating system, and it is necessary to standardise methodology for such analyses in Europe, taking into account local variability, to allow comparison of results.
TL;DR: It is demonstrated that this probiotic yeast secreted by S. boulardii secretes into the medium active compounds reducing candidal virulence factors, which is responsible for inhibition of C. albicans filamentation and partially also adhesion and biofilm formation.
Abstract: Candidiasis are life-threatening systemic fungal diseases, especially of gastro intestinal track, skin and mucous membranes lining various body cavities like the nostrils, the mouth, the lips, the eyelids, the ears or the genital area. Due to increasing resistance of candidiasis to existing drugs, it is very important to look for new strategies helping the treatment of such fungal diseases. One promising strategy is the use of the probiotic microorganisms, which when administered in adequate amounts confer a health benefit. Such a probiotic microorganism is yeast Saccharomyces boulardii, a close relative of baker yeast. Saccharomyces boulardii cells and their extract affect the virulence factors of the important human fungal pathogen C. albicans, its hyphae formation, adhesion and biofilm development. Extract prepared from S. boulardii culture filtrate was fractionated and GC-MS analysis showed that the active fraction contained, apart from 2-phenylethanol, caproic, caprylic and capric acid whose presence was confirmed by ESI-MS analysis. Biological activity was tested on C. albicans using extract and pure identified compounds. Our study demonstrated that this probiotic yeast secretes into the medium active compounds reducing candidal virulence factors. The chief compound inhibiting filamentous C. albicans growth comparably to S. boulardii extract was capric acid, which is thus responsible for inhibition of hyphae formation. It also reduced candidal adhesion and biofilm formation, though three times less than the extract, which thus contains other factors suppressing C. albicans adherence. The expression profile of selected genes associated with C. albicans virulence by real-time PCR showed a reduced expression of HWP1, INO1 and CSH1 genes in C. albicans cells treated with capric acid and S. boulardii extract. Hence capric acid secreted by S. boulardii is responsible for inhibition of C. albicans filamentation and partially also adhesion and biofilm formation.
TL;DR: In this paper, a two-terminal impedance-based fault-location algorithm is presented, which takes into account the distributed parameter line model and utilizes unsynchronized measurements of voltages and currents from two ends of a line and is formulated in terms of the fundamental frequency phasors of symmetrical components of the measured signals.
Abstract: This paper presents a new two-terminal impedance-based fault-location algorithm, which takes into account the distributed parameter line model. The algorithm utilizes unsynchronized measurements of voltages and currents from two ends of a line and is formulated in terms of the fundamental frequency phasors of symmetrical components of the measured signals. First, an analytical synchronization of the unsynchronized measurements is performed with use of the determined synchronization operator. Then, the distance to fault is calculated as for the synchronized measurements. Simultaneous usage of two kinds of symmetrical components for determining the synchronization operator makes that the calculations are simple, noniterative, and at the same time highly accurate. The developed fault-location algorithm has been thoroughly tested using signals of Alternate Transients Program-Electromagnetic Transients Program versatile simulations of faults on a transmission line. The presented evaluation shows the validity of the developed fault-location algorithm and its high accuracy.
TL;DR: Recent biochemical, structural and functional studies provide the substrate specificity and mechanistic binding data needed to guide the development of more potent anti-malarial drugs, and form the rationale for choosing PfM1AAP and PfM17LAP as targets for anti- malarial development.
TL;DR: In this article, a theory of excitonic processes in gate controlled graphene quantum dots is presented, and the dependence of the energy gap on shape, size, and edge for graphene quantum dot with up to a million atoms is predicted.
Abstract: We present a theory of excitonic processes in gate controlled graphene quantum dots. The dependence of the energy gap on shape, size, and edge for graphene quantum dots with up to a million atoms is predicted. Using a combination of tight-binding, Hartree-Fock and configuration interaction methods, we show that triangular graphene quantum dots with zigzag edges exhibit optical transitions simultaneously in the terahertz, visible and UV spectral ranges, determined by strong electron-electron and excitonic interactions. The relationship between optical properties and finite magnetic moment and charge density controlled by an external gate is predicted.
TL;DR: Here, several approaches for the design of inhibitors for metallo-aminopeptidases are presented and the optimized structures should be considered as potential leads in the drug discovery process against endogenous and infectious diseases.
24 Mar 2010
TL;DR: There is no single algorithm which produces the best ensembles and it is worth to seek an optimal hybrid multi-model solution.
Abstract: The experiments, aimed to compare three methods to create ensemble models implemented in a popular data mining system called WEKA, were carried out. Six common algorithms comprising two neural network algorithms, two decision trees for regression, linear regression, and support vector machine were used to construct ensemble models. All algorithms were employed to real-world datasets derived from the cadastral system and the registry of real estate transactions. Nonparametric Wilcoxon signed-rank tests to evaluate the differences between ensembles and original models were conducted. The results obtained show there is no single algorithm which produces the best ensembles and it is worth to seek an optimal hybrid multi-model solution.
TL;DR: In this article, a modification of the least squares Prony's method for power quality analysis in terms of estimation of harmonics and interharmonics in an electric power signal is presented.
Abstract: This paper presents a new modification of the least-squares Prony's method for power-quality analysis in terms of estimation of harmonics and interharmonics in an electric power signal. The so-called reduced Prony's method can be competitive, in some specific case, to the Fourier transformation method and the classical LS Prony's method. The modification constitutes in a specific selection of a constant frequency vector in a Fourier-like manner leading to a remarkable reduction of the computational burden and enabling online real-time computations. In addition, a sampling frequency and an analysis window length can be selected to provide the numerical stability of the new algorithm.
TL;DR: A Langevin-type model of subdiffusion with tempered α-stable waiting times with general properties of tempered anomalous diffusion is introduced and the form of the fractional Fokker-Planck equation corresponding to the tempered sub Diffusion is found.
Abstract: In this paper we introduce a Langevin-type model of subdiffusion with tempered α-stable waiting times. We consider the case of space-dependent external force fields. The model displays subdiffusive behavior for small times and it converges to standard Gaussian diffusion for large time scales. We derive general properties of tempered anomalous diffusion from the theory of tempered α-stable processes, in particular we find the form of the fractional Fokker-Planck equation corresponding to the tempered subdiffusion. We also construct an algorithm of simulation of sample paths of the introduced process. We apply the algorithm to approximate solutions of the fractional Fokker-Planck equation and to study statistical properties of the tempered subdiffusion via Monte Carlo methods.
TL;DR: This work determined the substrate specificity of human, pig, and rat orthologs of aminopeptidase N (CD13), a highly conserved cell surface protease that inactivates enkephalins and other bioactive peptides and reveals a relationship between the Kinetics of substrate hydrolysis and the kinetics of enzyme inhibition.
TL;DR: In this paper, reference values for the content of elements in human hair were elaborated, for which reference ranges were determined and considered as the values between 10th and 90th percentile.
TL;DR: In this article, the balance of axial forces produced in high-speed bearing systems with angular contact ball bearings is examined, with a particular consideration of centrifugal forces, gyroscopic moments, contact deformations, and contact angles.
TL;DR: To eliminate the chattering phenomenon related to the sliding-mode control, a switching function with a variable slope based on the fuzzy system is implemented, which ensures the robustness and dynamics of a two-mass drive better than with a linear speed controller.
Abstract: This paper presents a modified sliding-mode structure implemented for the speed control of a two-mass drive. A characteristic feature of the presented control method is the higher rank of the switching function caused by the application of an integral element (sliding mode with an integral function control). The proposed control system is a combination of a sliding-mode controller and a linear controller. Furthermore, to eliminate the chattering phenomenon related to the sliding-mode control, a switching function with a variable slope based on the fuzzy system is implemented. This solution ensures the robustness and dynamics of a two-mass drive better than with a linear speed controller. The main stages of the design methodology of the presented speed control structure are described in the initial sections of this paper. In the subsequent sections, simulation and experimental tests for the proposed control structure are presented and discussed.
TL;DR: It is shown that the sample (time average) mean-squared displacement (MSD) of the fractional Lévy α -stable motion behaves very differently from the corresponding ensemble average (second moment), while the ensemble average MSD diverges for α<2 .
Abstract: We show in this paper that the sample time average mean-squared displacement MSD of the fractional Levy -stable motion behaves very differently from the corresponding ensemble average second moment. While the ensemble average MSD diverges for 2, the sample MSD may exhibit either subdiffusion, normal diffusion, or superdiffusion. Thus, H-self-similar Levy stable processes can model either a subdiffusive, diffusive or superdiffusive dynamics in the sense of sample MSD. We show that the character of the process is controlled by a sign of the memory parameter d =H �1 /. We also introduce a sample p-variation dynamics test which allows to distinguish between two models of subdiffusive dynamics. Finally, we illustrate a subdiffusive behavior of the fractional Levy stable motion on biological data describing the motion of individual fluorescently labeled mRNA molecules inside live E. coli cells, but it may concern many other fields of contemporary experimental physics. DOI: 10.1103/PhysRevE.82.021130
TL;DR: Using an existing database based on measurements carried out on a construction site, an artificial neural network was built to predict productivity for selected sets of machines and to calculate the task execution time and cost.
TL;DR: In this article, a 2-in c-plane GaN seeds are shown to exhibit intrinsic narrow exciton lines, which are very sensitive to the optical selection rules typical for hexagonal symmetry, proving the truly nonpolar character of such AMMONO-GaN substrates.