Wyniki wyszukiwania

Filtruj wyniki

  • Czasopisma
  • Autorzy
  • Słowa kluczowe
  • Data
  • Typ

Wyniki wyszukiwania

Wyników: 23
Wyników na stronie: 25 50 75
Sortuj wg:

Abstrakt

Zdobywanie na studiach kompetencji do nauczania matematyki w klasach najmłodszych przez wiele lat kojarzyło się z umiejętnością odtwórczego aplikowania wytycznych metodyki. Obecnie dostrzega się konieczność rozumienia, jakie znaczenia nadają pojęciom matematycznym z tego zakresu nie tylko nauczyciele, ale również studenci tej specjalności. W artykule podjęto próbę włączenia się w interpretacyjny nurt myślenia o edukacji matematyki, pokazanego z perspektywy studentów przygotowywanych do zawodu nauczyciela wczesnej edukacji. Rozumienie przez nich kontekstów poznawania pojęć matematycznych i wrażliwość na procesy konstruowania wiedzy matematycznej przez najmłodszych uczniów jest predykatorem działań edukacyjnych podejmowanych w przyszłości w klasie szkolnej. Tekst jest efektem dokonania jakościowych analiz pisemnych wypowiedzi studentów wczesnej edukacji. Respondenci musieli dokonać pewnej konceptualizacji własnych przekonań przez uzasadnienie wyboru określonych deklaratywnych wypowiedzi. Znaczenia matematyczne studentów odsłaniane były również w strategiach rozwiązywania zadań matematycznych dla najmłodszych uczniów. Wyniki tych badań stanowią kontekst odczytywania studenckiego rozumienia procesów poznawania matematyki.
Przejdź do artykułu

Abstrakt

The paper is concerned with issues of the estimation of random variable distribution parameters by the Monte Carlo method. Such quantities can correspond to statistical parameters computed based on the data obtained in typical measurement situations. The subject of the research is the mean, the mean square and the variance of random variables with uniform, Gaussian, Student, Simpson, trapezoidal, exponential, gamma and arcsine distributions.
Przejdź do artykułu

Abstrakt

The article shows that during the forming of grammatical category of gender in Indo-European languages, names of non-living objects and names of those animals whose sex is unimportant for humans were receiving grammatical meanings of gender on the basis of similarity or dissimilarity of designated objects with males or females. Such grammatical metaphors were based on the ideas of different peoples about some minor characteristics of persons of different sex, such as the difference between men and women with higher activity, greater size, strength and independence. By now, the metaphorical motivation of category of gender in the Russian language has survived only in certain nouns. These nouns are interrogative pronouns кто (masc.) ʻwhoʼ and что (neut.) ʻwhatʼ, paired nouns-synonyms, e. g. конь (masc.) ʻstrong horseʼ – лошадь (fem.) ʻordinary horseʼ, generic versions of nouns, e. g. ворон (masc.) ʻravenʼ – ворона (fem.) ʻcrowʼ, and nouns-occasionalisms used in speech oriented to expressiveness and creativity.
Przejdź do artykułu

Abstrakt

Speech enhancement objective is to improve the noisy speech signals for human perception. The intention of speech enhancement algorithm is to improve the performance of the communication, when the signal is occluded by noise. The quality and intelligibility of speech is reduced because of the presence of background noise. There are various adaptive filtering algorithms for speech enhancement. The existing least mean square and normalised least mean square algorithms have the problem of choosing the step size that guarantees the stability of the algorithm. To overcome this problem, we focus on speech enhancement by amended adaptive filtering. The proposed algorithm follows blind source separation strategy using adaptive filtering. Comparison of existing adaptive filtering algorithms with proposed algorithm justifies the amendment incorporated in this paper. Taking the objective criteria into account the algorithms has been tested for segmental signal to noise ratio (SegSNR), segmental mean square error (SegMSE), signal to noise ratio and mean square error. The proposed algorithm can be used for hand-free cell phone, hearing aids and teleconferencing systems.
Przejdź do artykułu

Abstrakt

Głównym celem artykułu jest przedstawienie i porównanie niektórych aspektów referencyjnej teorii znaczenia Hilarego Putnama i inferencyjnej teorii znaczenia Roberta B. Brandoma. Ma to służyć pokazaniu podobieństw i różnic tych teorii, a dzięki temu ich głębszemu zrozumieniu i trafniejszej ocenie jak te teorie opisują i wyjaśniają proces nabywania znaczenia przez wyrażenia językowe. W swej teorii znaczenia Putnam akcentuje referencję pojętą jako relacja łącząca wyrażenia językowe z rzeczywistością pozajęzykową (empiryczną). Natomiast Brandom podkreśla doniosłość inferencji, dzięki której dookreślane jest znaczenie wyrażeń użytych w przesłankach i wniosku wnioskowania. Jednak wobec jego teorii znaczenia stawiany jest zarzut, że minimalizuje ona rolę elementu empirycznego (wyrażeń wskazujących itp.). Próbuje on bronić swojego stanowiska w anaforycznej teorii referencji. Putnam podobnie jak i Brandom twierdzili, że – jako podmioty poznające rzeczywistość pozajęzykową – nie jesteśmy w sytuacji, w której rzeczywistość dociera do nas w sposób bezpośredni. W poznaniu rzeczywistości odgrywa rolę sama rzeczywistość, ale i to jaka jest nasza aparatura poznawcza.
Przejdź do artykułu

Abstrakt

Celem tekstu jest rozważenie niedostatecznie dotąd opracowanego problemu miejsca języka w myśli Karola Marksa. W pierwszej części artykułu omówionych zostaje kilka przykładów marksistowskich prób filozoficznej lub językoznawczej refleksji nad językiem. Stawiam tezę, że marksistowska teoria znaczenia nie rozwinęła się jako nurt współczesnej myśli ze względu na dominację „tradycyjnej teorii znaczenia” (TTZ) – abstrahującej od konkretnych społecznych uwarunkowań. W drugiej części wskazuję na dające się odnaleźć u Marksa zapowiedzi tendencji obecnych we współczesnej filozofii języka, takich jak eksternalizm czy pragmatyzm. Jednocześnie zaznaczam, że w kontekście materializmu historycznego nabierają one charakteru, który każe wyjść poza TTZ. Następnie argumentuję, że teoria języka z wykorzystaniem koncepcji podziału pracy językowej pozwala rozwiązać pewne trudności związane z Marksa koncepcją ideologii.
Przejdź do artykułu

Abstrakt

Numerical methods are mostly used to predict the acoustic pressure inside duct systems. In this paper, the development of a numerical method based on the convected Helmholtz equation to compute the acoustic pressure inside an axisymmetric duct is presented. A validation of the proposed method was done by a comparison with the analytical formulation for simple cases of hard wall and lined ducts. The effect of the flow on the acoustic pressure inside these ducts was then evaluated by computing this field with different Mach numbers.
Przejdź do artykułu

Abstrakt

One of the important parameters describing pneumatic liquid atomisation is the air to liquid mass ratio (ALR). Along with the atomiser design and properties of the liquid it has extremely important influence on parameters of atomised liquid such as: mean droplet diameter, jet range and angle. Knowledge about real characteristics of an atomiser in this respect is necessary to correctly choose its operating parameters in industrial applications. The paper presents results of experimental research of two-fluid atomisers with internal mixing built according to custom design. Investigated atomizers were designed for spraying a urea aqueous solution inside the power boiler combustion chamber. They are an important element of SNCR (selective non-catalytic reduction) installation which is used to reduce nitrogen oxides in a flue gas boiler. Obtained results were used by authors in further research, among others to determine the boundary conditions in the SNCR installation modeling. The research included determining mean droplet diameter as a function of ALR. It has been based on the immersion liquid method and on the use of specialised instrumentation for determining distribution of droplet diameters in a spray – Spraytec by Malvern. Results obtained with both methods were later compared. The measurements were performed at a laboratory stand located at the Institute of Heat Engineering, Warsaw University of Technology. The stand enables extensive investigation of the water atomisation process.
Przejdź do artykułu

Abstrakt

In the study we introduce an extension to a stochastic volatility in mean model (SV-M), allowing for discrete regime switches in the risk premium parameter. The logic behind the idea is that neglecting a possibly regimechanging nature of the relation between the current volatility (conditional standard deviation) and asset return within an ordinary SV-M specication may lead to spurious insignicance of the risk premium parameter (as being ‛averaged out’ over the regimes). Therefore, we allow the volatility-in-mean eect to switch over dierent regimes according to a discrete homogeneous two-state Markov chain. We treat the new specication within the Bayesian framework, which allows to fully account for the uncertainty of model parameters, latent conditional variances and hidden Markov chain state variables. Standard Markov Chain Monte Carlo methods, including the Gibbs sampler and the Metropolis-Hastings algorithm, are adapted to estimate the model and to obtain predictive densities of selected quantities. Presented methodology is applied to analyse series of the Warsaw Stock Exchange index (WIG) and its sectoral subindices. Although rare, once spotted the switching in-mean eect substantially enhances the model t to the data, as measured by the value of the marginal data density.
Przejdź do artykułu

Abstrakt

The recently proposed q-rung orthopair fuzzy set (q-ROFS) characterized by a membership degree and a non-membership degree is powerful tool for handling uncertainty and vagueness. This paper proposes the concept of q-rung orthopair linguistic set (q-ROLS) by combining the linguistic term sets with q-ROFSs. Thereafter, we investigate multi-attribute group decision making (MAGDM) with q-rung orthopair linguistic information. To aggregate q-rung orthopair linguistic numbers ( q-ROLNs), we extend the Heronian mean (HM) to q-ROLSs and propose a family of q-rung orthopair linguistic Heronian mean operators, such as the q-rung orthopair linguistic Heronian mean (q-ROLHM) operator, the q-rung orthopair linguistic weighted Heronian mean (q-ROLWHM) operator, the q-rung orthopair linguistic geometric Heronian mean (q-ROLGHM) operator and the q-rung orthopair linguistic weighted geometric Heronian mean (q-ROLWGHM) operator. Some desirable properties and special cases of the proposed operators are discussed. Further, we develop a novel approach to MAGDM within q-rung orthopair linguistic context based on the proposed operators. A numerical instance is provided to demonstrate the effectiveness and superiorities of the proposed method.
Przejdź do artykułu

Abstrakt

The paper presents the results of investigating the effect of increase of observation correlations on detectability and identifiability of a single gross error, the outlier test sensitivity and also the response-based measures of internal reliability of networks. To reduce in a research a practically incomputable number of possible test options when considering all the non-diagonal elements of the correlation matrix as variables, its simplest representation was used being a matrix with all non-diagonal elements of equal values, termed uniform correlation. By raising the common correlation value incrementally, a sequence of matrix configurations could be obtained corresponding to the increasing level of observation correlations. For each of the measures characterizing the above mentioned features of network reliability the effect is presented in a diagram form as a function of the increasing level of observation correlations. The influence of observation correlations on sensitivity of the w -test for correlated observations (Förstner 1983,Teunissen 2006) is investigated in comparison with the original Baarda’s w -test designated for uncorrelated observations, to determine the character of expected sensitivity degradation of the latter when used for correlated observations. The correlation effects obtained for different reliability measures exhibit mutual consistency in a satisfactory extent. As a by-product of the analyses, a simple formula valid for any arbitrary correlation matrix is proposed for transforming the Baarda’s w -test statistics into the w -test statistics for correlated observations.
Przejdź do artykułu

Abstrakt

The correlation of data contained in a series of signal sample values makes the estimation of the statistical characteristics describing such a random sample difficult. The positive correlation of data increases the arithmetic mean variance in relation to the series of uncorrelated results. If the normalized autocorrelation function of the positively correlated observations and their variance are known, then the effect of the correlation can be taken into consideration in the estimation process computationally. A significant hindrance to the assessment of the estimation process appears when the autocorrelation function is unknown. This study describes an application of the conditional averaging of the positively correlated data with the Gaussian distribution for the assessment of the correlation of an observation series, and the determination of the standard uncertainty of the arithmetic mean. The method presented here can be particularly useful for high values of correlation (when the value of the normalized autocorrelation function is higher than 0.5), and for the number of data higher than 50. In the paper the results of theoretical research are presented, as well as those of the selected experiments of the processing and analysis of physical signals.
Przejdź do artykułu

Abstrakt

This paper presents a numerical analysis of an agitated fully baffled cylindrical vessel with a down pumping four blade worn or unworn pitched blade impeller (α = 45° and 30°) under a turbulent flow regime. CFD simulations predict the pumping capacity of the system equipped by worn and unworn pitched blade impeller. Experimental data were taken from the authors’ previous work and compared with results of numerical computations. A good agreement with experimental data was obtained. The ensemble-average mean velocity field with worn and unworn impellers was computed. It follows from the simulation results that the wear rate of the impeller blade has a significantly negative effect on the velocity distribution in an agitated liquid. The greater the destruction of the worn blade, the higher is the deformation of the velocity field around the rotating impeller, with a simultaneous decrease in impeller pumping capacity.
Przejdź do artykułu

Abstrakt

The velocity field around the standard Rushton turbine was investigated by the Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV) measurements. The mean ensembleaveraged velocity profiles and root mean square values of fluctuations were evaluated at two different regions. The first one was in the discharge stream in the radial direction from the impeller where the radial flow is dominant and it is commonly modelled as a swirling turbulent jet. The validity range of the turbulent jet model was studied. The second evaluated region is under the impeller where flow seems to be at first sight rather rigorous but obtained results show nonnegligible values of fluctuation velocity.
Przejdź do artykułu

Abstrakt

The aim of the article is to construct an asymptotically consistent test, based on a subsampling approach, to verify hypothesis about existence of the individual or common deterministic cycle in coordinates of multivariate macroeconomic time series. By the deterministic cycle we mean the periodic or almost periodic fluctuations in the mean function in cyclical fluctuations. To construct test we formulate a multivariate non-parametric model containing the business cycle component in the unconditional mean function. The construction relies on the Fourier representation of the unconditional expectation of the multivariate Almost Periodically Correlated time series and is related to fixed deterministic cycle presented in the literature. The analysis of the existence of common deterministic business cycles for selected European countries is presented based on monthly industrial production indexes. Our main findings from the empirical part is that the deterministic cycle can be strongly supported by the data and therefore should not be automatically neglected during analysis without justification.
Przejdź do artykułu

Abstrakt

In the areas of acoustic research or applications that deal with not-precisely-known or variable conditions, a method of adaptation to the uncertainness or changes is usually necessary. When searching for an adaptation algorithm, it is hard to overlook the least mean squares (LMS) algorithm. Its simplicity, speed of computation, and robustness has won it a wide area of applications: from telecommunication, through acoustics and vibration, to seismology. The algorithm, however, still lacks a full theoretical analysis. This is probabely the cause of its main drawback: the need of a careful choice of the step size - which is the reason why so many variable step size flavors of the LMS algorithm has been developed. This paper contributes to both the above mentioned characteristics of the LMS algorithm. First, it shows a derivation of a new necessary condition for the LMS algorithm convergence. The condition, although weak, proved useful in developing a new variable step size LMS algorithm which appeared to be quite different from the algorithms known from the literature. Moreover, the algorithm proved to be effective in both simulations and laboratory experiments, covering two possible applications: adaptive line enhancement and active noise control.
Przejdź do artykułu

Abstrakt

The study aims at a statistical verification of breaks in the risk-return relationship for shares of individual companies quoted at the Warsaw Stock Exchange. To this end a stochastic volatility model incorporating Markov switching in-mean effect (SV-MS-M) is employed. We argue that neglecting possible regime changes in the relation between expected return and volatility within an ordinary SV-M specification may lead to spurious insignificance of the risk premium parameter (as being ’averaged out’ over the regimes).Therefore, we allow the volatility-in-mean effect to switch over different regimes according to a discrete homogeneous two- or three-state Markov chain. The model is handled within Bayesian framework, which allows to fully account for the uncertainty of model parameters, latent conditional variances and state variables. MCMC methods, including the Gibbs sampler, Metropolis-Hastings algorithm and the forward-filtering-backward-sampling scheme are suitably adopted to obtain posterior densities of interest as well as marginal data density. The latter allows for a formal model comparison in terms of the in-sample fit and, thereby, inference on the ’adequate’ number of the risk premium regime
Przejdź do artykułu

Abstrakt

Cooling is indispensable for maintaining the desired performance and reliability over a very huge variety of products like electronic devices, computer, automobiles, high power laser system etc. Apart from the heat load amplification and heat fluxes caused by many industrial products, cooling is one of the major technical challenges encountered by the industries like manufacturing sectors, transportation, microelectronics, etc. Normally water, ethylene glycol and oil are being used as the fluid to carry away the heat in these devices. The development of nanofluid generally shows a better heat transfer characteristics than the water. This research work summarizes the experimental study of the forced convective heat transfer and flow characteristics of a nanofluid consisting of water and 1% Al2O3(volume concentration) nanoparticle flowing in a parallel flow, counter flow and shell and tube heat exchanger under laminar flow conditions. The Al2O3 nanoparticles of about 50 nm diameter are used in this work. Three different mass flow rates have been selected and the experiments have been conducted and their results are reported. This result portrays that the overall heat transfer coefficient and dimensionless Nusselt number of nanofluid is slightly higher than that of the base liquid at same mass flow rate at same inlet temperature. From the experimental result it is clear that the overall heat transfer coefficient of the nanofluid increases with an increase in the mass flow rate. It shows that whenever mass flow rate increases, the overall heat transfer coefficient along with Nusselt number eventually increases irrespective of flow direction. It was also found that during the increase in mass flow rate LMTD value ultimately decreases irrespective of flow direction. However, shell and tube heat exchanger provides better heat transfer characteristics than parallel and counter flow heat exchanger due to multi pass flow of nanofluid. The overall heat transfer coefficient, Nusselt number and logarithmic mean temperature difference of the water and Al2O3/water nanofluid are also studied and the results are plotted graphically.
Przejdź do artykułu

Abstrakt

In this paper, we investigate the multiple attribute decision making problems based on the Bonferroni mean operators with dual Pythagorean hesitant fuzzy information. Firstly, we introduce the concept and basic operations of the dual hesitant Pythagorean fuzzy sets, which is a new extension of Pythagorean fuzzy sets. Then, motivated by the idea of Bonferroni mean operators, we have developed some Bonferroni mean aggregation operators for aggregating dual hesitant Pythagorean fuzzy information. The prominent characteristic of these proposed operators are studied. Then, we have utilized these operators to develop some approaches to solve the dual hesitant Pythagorean fuzzy multiple attribute decision making problems. Finally, a practical example for supplier selection in supply chain management is given to verify the developed approach and to demonstrate its practicality and effectiveness.
Przejdź do artykułu

Abstrakt

Multiple Input Multiple Output (MIMO (techniques use multiple antennas at both transmitter and receiver for increasing the channel reliability and enhancing the spectral efficiency of wireless communication system.MIMO Spatial Multiplexing (SM) is a technology that can increase the channel capacity without additional spectral resources. The implementation of MIMO detection techniques become a difficult mission as the computational complexity increases with the number of transmitting antenna and constellation size. So designing detection techniques that can recover transmitted signals from Spatial Multiplexing (SM) MIMO with reduced complexity and high performance is challenging. In this survey, the general model of MIMO communication system is presented in addition to multiple MIMO Spatial Multiplexing (SM) detection techniques. These detection techniques are divided into different categories, such as linear detection, Non-linear detection and tree-search detection. Detailed discussions on the advantages and disadvantages of each detection algorithm are introduced. Hardware implementation of Sphere Decoder (SD) algorithm using VHDL/FPGA is also presented.
Przejdź do artykułu

Abstrakt

The MDCT and IntMDCT Algorithm is widely utilized is Audio coding. By lifting scheme or rounding operation IntegerMDCT is evolved from Modified Discrete Cosine Transform. This method acquire the properties of MDCT and contribute excelling invertiblity and good spectral mean .In this paper we discuss about the audio codec like AAC and FLAC using MDCT and Integer MDCT algorithm and to find which algorithm shows better Compression Ratio(CR).The confines of this task is to hybriding lossy and lossless audio codec with diminished bit rate but with finer sound quality. Certainly the quality of the audio is figure out by Subjective and Objective testing which is in terms of MOS (Mean opinion square), ABx and some of the hearing aid testing methodology like PEAQ(Perceptual Evaluation Audio Quality) and ODG(Objective Difference Grade)is followed. Execution measure, that is Compression Ratio(CR) and Sound Pressure Level (SPL) is approximated.
Przejdź do artykułu

Abstrakt

The use of quantitative methods, including stochastic and exploratory techniques in environmental studies does not seem to be sufficient in practical aspects. There is no comprehensive analytical system dedicated to this issue, as well as research regarding this subject. The aim of this study is to present the Eco Data Miner system, its idea, construction and implementation possibility to the existing environmental information systems. The methodological emphasis was placed on the one-dimensional data quality assessment issue in terms of using the proposed QAAH1 method - using harmonic model and robust estimators beside the classical tests of outlier values with their iterative expansions. The results received demonstrate both the complementarity of proposed classical methods solution as well as the fact that they allow for extending the range of applications significantly. The practical usefulness is also highly significant due to the high effectiveness and numerical efficiency as well as simplicity of using this new tool.
Przejdź do artykułu

Ta strona wykorzystuje pliki 'cookies'. Więcej informacji