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Number of results: 28
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Abstract

This paper presents a method of correcting the effects caused by refraction phenomena in an optical measurement system. The correction algorithm proposed can be applied in many different photogrammetric applications affected by these effects. To validate this algorithm, a foot sole optical measurement system that uses several cameras to build a mesh of a foot sole has been used. This measurement system has six cameras that are protected by a safety glass that separates the cameras from the foot to be measured. The safety glass produces an air-glass-air interface that causes the refraction phenomena, producing deformations in the images. Due to the deformations it is impossible to obtain reliable metric information of the images captured using the measurement system. The developed correction algorithm is based on a grid layout and associated polynomials and makes it possible to correct the deformations and extract accurate metric information.
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Abstract

In the article a non-uniformity correction method is presented which allows to compensate for the influence of detector’s temperature drift. For this purpose, dependency between output signal value and the temperature of the detector array was investigated. Additionally the influence of the temperature on the Offset and Gain coefficients was measured. Presented method utilizes estimated dependency between output signal of detectors and their temperature. In the presented method, the shutter is used for establishing signal reference. Thermoelectric cooler is used for changing the temperature of the detector array.
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Abstract

This paper researches the application of grey system theory in cost forecasting of the coal mine. The grey model (GM(1.1)) is widely used in forecasting in business and industrial systems with advantages of minimal data, a short time and little fluctuation. Also, the model fits exponentially with increasing data more precisely than other prediction techniques. However, the traditional GM(1.1) model suffers from the poor anti-interference ability. Aimed at the flaws of the conventional GM(1.1) model, this paper proposes a novel dynamic forecasting model with the theory of background value optimization and Fourier-series residual error correction based on the traditional GM(1.1) model. The new model applies the golden segmentation optimization method to optimize the background value and Fourier-series theory to extract periodic information in the grey forecasting model for correcting the residual error. In the proposed dynamic model, the newest data is gradually added while the oldest is removed from the original data sequence. To test the new model’s forecasting performance, it was applied to the prediction of unit costs in coal mining, and the results show that the prediction accuracy is improved compared with other grey forecasting models. The new model gives a MAPE & C value of 0.14% and 0.02, respectively, compared to 1.75% and 0.37 respectively for the traditional GM(1.1) model. Thus, the new GM(1.1) model proposed in this paper, with advantages of practical application and high accuracy, provides a new method for cost forecasting in coal mining, and then help decision makers to make more scientific decisions for the mining operation.
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Abstract

A high pressure resonator transducer (0 to 100 MPa) devised by the author has been described. The elastic element of the converter consists of a cylinder with an offset arranged axis hole. Quartz resonators were used for the measurement of deformations of the pipe. Based upon the results of the transducer testing, a new algorithmic method for the minimizalizsation of the temperature error, that eliminates the need for a temperature gauge has been worked out.
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Abstract

Qualitative and quantitative results of high terrain elevation effect on spectral radiance of optical satellite image which affect the accuracy in retrieving of land surface cover changes is given. The paper includes two main parts: correction model of spectral radiance of satellite image affected by high terrain elevation and assessment of impacts and variation of land cover changes before and after correcting influence of high terrain elevation to the spectral radiance of the image. Study has been carried out with SPOT 5 in Hoa Binh mountain area of two periods: 2007 and 2010. Results showed that appropriate correction model is the Meyer’s one. The impacts of correction spectral radiance to 7 classes of classified images fluctuate from 15% to 400%. The varying changes before and after correction of image radiation fluctuate over 7 classes from 5% to 100%.
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Abstract

The aim of the study is to discuss the relationship of the crude oil price, speculative activity and fundamental factors. An empirical study was conducted with a VEC model. Two cointegrating vectors were identified. The first vector represents the speculative activity. We argue that the number of short non-commercial positions increases with the crude oil stock and price, decreases with the higher number of long non-commercial positions. A positive trend of crude oil prices may be a signal for traders outside the industry to invest in the oil market, especially as access to information could be limited for them. The second vector represents the crude oil price under the fundamental approach. The results support the hypothesis that the crude oil price is dependent on futures trading. The higher is a number of commercial long positions, the greater is the pressure on crude oil price to increase.
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Abstract

In the article we address matters related to the stability of motion of the car subjected to the external lateral force. We show the possibility to compensate the effect of the external forces my means of the steering wheel angle. We have carried out the analysis for bicycle scheme vehicle and four-wheel model according to linear and nonlinear drift hypothesis. We have considered influence of speed of the car and size of external side force for the period of transition processes of stabilization of the movement.
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Abstract

The paper addresses the problem of the automatic distortion removal from images acquired with non-metric SLR camera equipped with prime lenses. From the photogrammetric point of view the following question arises: is the accuracy of distortion control data provided by the manufacturer for a certain lens model (not item) sufficient in order to achieve demanded accuracy? In order to obtain the reliable answer to the aforementioned problem the two kinds of tests were carried out for three lens models. Firstly the multi-variant camera calibration was conducted using the software providing full accuracy analysis. Secondly the accuracy analysis using check points took place. The check points were measured in the images resampled based on estimated distortion model or in distortion-free images simply acquired in the automatic distortion removal mode. The extensive conclusions regarding application of each calibration approach in practice are given. Finally the rules of applying automatic distortion removal in photogrammetric measurements are suggested
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Abstract

This paper presents two methods for evaluation of the effective wavenumber of nearly-Gaussian beams in laser interferometers that can be used for determination of a so called diffraction correction in absolute gravimeters. The first method, that can be simply used in situ, is an empirical procedure based on the evaluation of the variability of g measurements against the amount of light limited by an iris diaphragm and transmitted to a photodetector. However, precision of this method depends on the beam quality similarly as in the case of the conventional method based on measurement of a beam width. The second method, that is more complex, is based on beam profiling in various distances and on calculation of the effective wavenumber using the second spatial derivative of a non-ideal beam field envelope. The measurement results achieved by both methods are presented on an example of two absolute gravimeters and the determined diffraction corrections are compared with the results obtained by measurements of beam width. Agreement of methods within about 1 mGal have been obtained with average diffraction corrections slightly exceeding +2 mGal for three FG5(X) gravimeter configurations.
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Abstract

The paper presents definitions and relative measures of the system sensitivity and sensitivity of its errors. The model of a real system and model of an ideal measuring system were introduced. It allows to determine the errors of the system. The paper presents also how to use the error sensitivity analysis carried out on the models of the measuring system to the correction of the nonlinearity error of its static characteristic. The corrective function is determined as a relation between the input variable of the tested system and its chosen parameter. The use of the proposed method has been presented on the example of a phase angle modulator. The obtained results have been compared with the results of analytic calculations. The idea of a phase angle modulator is also presented.
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Abstract

In the paper a method for correction of heating non-homogeneity applied in defect detection with the use of active thermography is presented. In the method an approximation of thermal background with second- and third-order surfaces was used, what made it possible to remove partially the background. In the paper the simulation results obtained with the abovementioned method are presented. An analysis of the influence of correction of heating non-homogeneity on the effectiveness of defect detection is also carried out. The simulations are carried out for thermograms obtained on the basis of experiments on a test sample with simulated defects, made of a material of low thermal diffusivity.
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Abstract

The main topic of this study is the experimental measurement and mathematical modelling of global gas hold-up and bubble size distribution in an aerated stirred vessel using the population balance method. The air-water system consisted of a mixing tank of diameter T = 0.29 m, which was equipped with a six-bladed Rushton turbine. Calculations were performed with CFD software CFX 14.5. Turbulent quantities were predicted using the standard k-ε turbulence model. Coalescence and breakup of bubbles were modelled using the homogeneous MUSIG method with 24 bubble size groups. To achieve a better prediction of the turbulent quantities, simulations were performed with much finer meshes than those that have been adopted so far for bubble size distribution modelling. Several different drag coefficient correlations were implemented in the solver, and their influence on the results was studied. Turbulent drag correction to reduce the bubble slip velocity proved to be essential to achieve agreement of the simulated gas distribution with experiments. To model the disintegration of bubbles, the widely adopted breakup model by Luo & Svendsen was used. However, its applicability was questioned.
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Abstract

This paper addresses the issue of obtaining maximum likelihood estimates of parameters for structural VAR models with a mixture of distributions. Hence the problem does not have a closed form solution, numerical optimization procedures need to be used. A Monte Carlo experiment is designed to compare the performance of four maximization algorithms and two estimation strategies. It is shown that the EM algorithm outperforms the general maximization algorithms such as BFGS, NEWTON and BHHH. Moreover, simplification of the problem introduced in the two steps quasi ML method does not worsen small sample properties of the estimators and therefore may be recommended in the empirical analysis.
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Abstract

Modernization of lands and buildings register, which is run in Poland now, assumes capturing boundaries location data by various methods. They are: direct measurement preceded by determining of boundaries in the presence of parties, photogram- metric method, cartographic method, using existing maps being in analogue form. These methods not always assure accuracy. In the paper, an idea of correcting of location of boundary points which do not fulfil accuracy requirements has been presented. These corrections have been computed by assumption of invariability of parcel area revealed in register, so far. Such way of operation from one side would avoid many misunderstandings and difficulties by applying data collected in cadastre and from the other side will not disturb used procedures, which aim is to determine boundary of parcels with demanded accuracy.
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Abstract

The paper presents the problem of assessing the accuracy of reconstructing free-form surfaces in the CMM/CAD/CAM/CNC systems. The system structure comprises a coordinate measuring machine (CMM) PMM 12106 equipped with a contact scanning probe, a 3-axis Arrow 500 Vertical Machining Center, QUINDOS software and Catia software. For the purpose of surface digitalization, a radius correction algorithm was developed. The surface reconstructing errors for the presented system were assessed and analysed with respect to offset points. The accuracy assessment exhibit error values in the reconstruction of a free-form surface in a range of ± 0.02 mm, which, as it is shown by the analysis, result from a systematic error.
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Abstract

Time-interleaved analog-to-digital converter (ADC) architecture is crucial to increase the maximum sample rate. However, offset mismatch, gain mismatch, and timing error between time-interleaved channels degrade the performance of time-interleaved ADCs. This paper focuses on the gain mismatch and timing error. Techniques based on Discrete Fourier Transform (DFT) for estimating and correcting gain mismatch and timing error in an M-channel ADC are depicted. Numerical simulations are used to verify the proposed estimation and correction algorithm.
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Abstract

The paper provides analysis of the influence of temperature on the error of weigh-in-motion (WIM) systems utilizing piezoelectric polymer load sensors. Results of tests of these sensors in a climatic chamber, as well as results of long-term tests at the WIM site, are presented. Different methods for correction of the influence of changes in temperature were assessed for their effectiveness and compared.
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Abstract

The economy of Slovakia experienced a turning point in the 1st half of 2008 and entered a phase of decline. The negative impacts of the global economic crisis became evident in the 2nd half of 2008 and led into a recession in the 1st quarter of 2009. The composite leading indicator was originally intended for forecasting of business cycle turning points between the decline and growth phases. The aim of this paper is to transform the qualitative information from composite leading indicator into quantitative forecast and verify whether the beginning of recession in Slovakia could have been identied in advance. The ARIMAX and error correction models are used for the composite reference series and GDP forecasts respectively. The nal result shows that the composite leading indicator is useful not only for identifying turning points, but also for the prediction of recession phase.
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Abstract

We develop a fully Bayesian framework for analysis and comparison of two competing approaches to modelling daily prices on different markets. The first approach, prevailing in financial econometrics, amounts to assuming that logarithms of prices behave like a multivariate random walk; this approach describes logarithmic returns most often by the VAR(1) model with MGARCH (or sometimes MSV) disturbances. In the second approach, considered here, it is assumed that daily price levels are linked together and, thus, the error correction term is added to the usual VAR(1)–MGARCH or VAR(1)–MSV model for logarithmic returns, leading to a reduced rank VAR(2) specification for logarithms of prices. The model proposed in the paper uses a hybrid MSV-MGARCH structure for VAR(2) disturbances. In order to keep cointegration modelling as simple as possible, we restrict to the case of two prices representing two different markets. The aim of the paper is to show how to check if a long-run relationship between daily prices exists and whether taking it into account influences our inference on volatility and short-run relations between returns on different markets. In the empirical example the daily values of the S&P500 index and the WTI oil price in the period 19.12.2005 – 30.09.2011 are jointly modelled. It is shown that, although the logarithms of the values of S&P500 and WTI oil price seem to be cointegrated, neglecting the error correction term leads to practically the same conclusions on volatility and conditional correlation as keeping it in the model.
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Abstract

The aim of this article is to present the design procedure for determining modification coefficients of toothed wheels of involutes planetary gear train with internal conjunction of teeth. It is possible to obtain a higher load-carrying capacity which depends also on correction coefficients. For example, we take into consideration a concept of planetary gears in which the teeth can be corrected, which allows better fatigue and contact surface strength. Two cases are considered when the namely zero center distance (without corrections) of the central and satellite wheels is the same or not, in relation to the zero center distance between the satellite and the sun wheel. Geometrical dimensions are described with regard to the technological teeth correction scope, and inequality restriction conditions are determined with respect to the ISO standards recommendations and the literature. The procedure can be applied to any other planetary gears with another kinematic connection of wheels.
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Abstract

In a PV-dominant DC microgrid, the traditional energy distribution method based on the droop control method has problems such as output voltage drop, insufficient power distribution accuracy, etc. Meanwhile, different battery energy storage units usually have different parameters when the system is running. Therefore, this paper proposes an improved control method that introduces a reference current correction factor, and a weighted calculation method for load power distribution based on the parameters of battery energy storage units is proposed to achieve weighted allocation of load power. In addition, considering the variation of bus voltage at the time of load mutation, voltage secondary control is added to realize dynamic adjustment of DC bus voltage fluctuation. The proposed method can achieve balance and stable operation of energy storage units. The simulation results verified the effectiveness and stability of the proposed control strategy.
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Abstract

Sample-time errors can greatly degrade the dynamic range of a time-interleaved sampling system. In this paper, a novel correction technique employing a cubic spline interpolation is proposed for inter-channel sample-time error compensation. The cubic spline interpolation compensation filter is developed in the form of a finite-impulse response (FIR) filter structure. The correction method of the interpolation compensation filter coefficients is deduced. A 4GS/s two-channel, time-interleaved ADC prototype system has been implemented to evaluate the performance of the technique. The experimental results showed that the correction technique is effective to attenuate the spurious spurs and improve the dynamic performance of the system.
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Abstract

The purpose of the article is to verify a hypothesis about the asymmetric pass-through of crude oil prices to the selling prices of refinery products (unleaded 95 petrol and diesel oil). The distribution chain is considered at three levels: the European wholesale market, the domestic wholesale market and the domestic retail market. The error correction model with threshold cointegration proved to be an appropriate tool for making an empirical analysis based on the Polish data. As found, price transmission asymmetry in the fuel market is significant and its scale varies depending on the level of distribution. The only exception is the wholesale price transmission to the domestic refinery price. All conclusions are supported by the cumulative response functions. The analysis sheds new light on the price-setting processes in an imperfectly competitive fuel market of a medium-sized, non-oil producing European country in transition.
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