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Number of results: 18
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Abstract

The aim of this study was to compare and analyze the gasification process of beech wood. The experimental investigation was conducted inside a gasifier, which can be operated in downdraft and updraft gasification system. The most important operating parameter studied in this paper was the influence of the amount of supply air on the temperature distribution, biomass consumption and syngas calorific value. The results show that the amount of air significantly influences the temperature in the combustion zone for the downdraft gasification process, where temperature differences reached more than 150 ◦C.The increased amount of air supplied to the gasifier caused an increase in fuel consumption for both experimental setups. Experimental results regarding equivalence ratio show that for value below 0.2, the updraft gasification is characterized by a higher calorific value of producer gas, while for about 0.22 a similar calorific value (6.5 MJ/Nm3) for both gasification configurations was obtained. Above this value, an increase in equivalence ratio causes a decrease in the calorific value of gas for downdraft and updraft gasifiers.
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Abstract

The paper deals with an application-specific integrated circuit (ASIC) facilitating voltage conversion in thermoelectric energy harvesters. The chip is intended to be used to boost up the voltage coming from a thermoelectric module to a level that is required by electronic circuits constituting wireless sensor nodes. The designed charge pump does not need any external parts for its proper operation because all the capacitors, switches and oscillator are integrated on the common silicon die. The topography of the main functional blocks and post-layout simulations of the designed integrated circuit are shown in the article.
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Abstract

The article presents the issues related to ecological security of the Baltic Sea. The issue was taken from the perspective of Poland as one of the Baltic States, and also as a Member State of the European Union. The authors discussed the mechanisms and legal instruments which are crucial for the ecological security of the Baltic Sea (i.e. Helsinki Convention of 1974, or Agenda 21 for the Baltic Sea Region “Baltic 21”). The importance of cross-border cooperation has also been emphasized as an essential element of the security policy in the Baltic Sea area. The article also indicated threats to the protection of Baltic waters, among others, eutrophication.
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Abstract

The article presents tests carried out on three selected samples of limestone originating from three commercially exploited deposits. The tests of sorbents included desulphurisation in different atmospheres and a physicochemical analysis of desulphurisation products. The aim of the tests was to determine desulphurisation efficiency and conversion degree as dependent on the concentration of O2 and CO2.
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Abstract

Whereas the use of biofuels has attracted increasing attention, the aim of this paper is to investigate the possibility of using sewage sludge as biofuel. Preparation of untreated and stabilised sludge with natural additives is described, as well as combusting method applied and experimental results of combusting are presented based on the assessment of composition of emitted pollutants and their concentrations in the exhaust gas. NOx formation in the exhaust gas has been analysed in depth. The results of investigations have shown that the use of dried sewage sludge possesses a positive energy balance. Therefore, the sludge may be used as fuel. The obtained experimental results demonstrate that during combustion, pollutant concentrations vary depending on oxygen content (O2), while formation of nitrogen oxides is strongly influenced by fuel-bound nitrogen. Also, a generalized equation of calculating fuel bound nitrogen conversion into NOx is presented.
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Abstract

The aim of the study was to evaluate the influence of different fillers on the chosen functional properties of experimental composites based on typical polymeric matrix, in order to understand the effect of different fillers on their properties and to develop a simple base composite for further investigations with experimental fillers, e.g. with antimicrobial properties. Previous experiments have been usually based on commercially available composites of unknown composition or compilation of monomers, without reinforcing fillers. Scanning electron microscopy was used to investigate the quality of fillers’ dispersion, which was satisfying. Results showed significant differences between materials’ diametral tensile strength (p = 0.0019), compressive strength (p < 0.0001), Vickers micro-hardness (p < 0.0001), flexural modules (p = 0.0018), and the degree of conversion (p < 0.0001), but flexural strength was not significantly different (p = 0.0583). Investigations indicated that no filler type had an especially positive impact on the mechanical properties, but reinforcement effect was achieved by proper compilation of silica nanofiller and variable glass fillers. Nanofiller decreased the degree of conversion.
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Abstract

Although the gas insulated structures have a high degree of reliability, the unavoidable defects are primary reason of their failures. Partial discharge (PD) has been regarded as an effective indication for condition monitoring and diagnosis of gas insulated switchgears (GISs) to ensure their reliable and stable operation. Among various PD detection methods, the ultra-high frequency (UHF) technique has the advantages of on-line motoring and defect classification. In this paper, there are presented 7 types of artificial electrode systems fabricated for simulation of real insulation defects in gas insulated structures. A real-time measurement system was developed to acquire defect patterns in a form of phase-resolve partial discharge (PRPD) intensity graph, using a UHF sensor. Further, the discharge distribution and statistical characteristics were extracted for defect identification using a neural network algorithm. In addition, a conversion experiment was proposed by detecting the PD pulse simultaneously using a non-induction resistor and a UHF sensor. A relationship between the magnitude of UHF signal and the amplitude of apparent charge was established, which was used for evaluation of PD using the UHF sensor.
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Abstract

In this paper a two-disc spinning disc reactor for intensified biodiesel synthesis is described and numerically simulated. The reactor consists of two flat discs, located coaxially and parallel to each other with a gap of 0.2 mm between the discs. The upper disc is located on a rotating shaft while the lower disc is stationary. The feed liquids, triglycerides (TG) and methanol are introduced coaxially along the centre line of rotating disc and stationary disc. Fluid hydrodynamics in the reactor for synthesis of biodiesel from TG and methanol in the presence of a sodium hydroxide catalyst are simulated, using convection-diffusion-reaction species transport model by the CFD software ANSYS©Fluent v. 13.0. The effect of the upper disc’s spinning speed is evaluated. The results show that the rotational speed increase causes an increase of TG conversion despite the fact that the residence time decreases. Compared to data obtained from adequate experiments, the model shows a satisfactory agreement.
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Abstract

A novel VC (voice conversion) method based on hybrid SVR (support vector regression) and GMM (Gaussian mixture model) is presented in the paper, the mapping abilities of SVR and GMM are exploited to map the spectral features of the source speaker to those of target ones. A new strategy of F0 transformation is also presented, the F0s are modeled with spectral features in a joint GMM and predicted from the converted spectral features using the SVR method. Subjective and objective tests are carried out to evaluate the VC performance; experimental results show that the converted speech using the proposed method can obtain a better quality than that using the state-of-the-art GMM method. Meanwhile, a VC method based on non-parallel data is also proposed, the speaker-specific information is investigated using the SVR method and preliminary subjective experiments demonstrate that the proposed method is feasible when a parallel corpus is not available.
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Abstract

In this paper a sample rate conversion algorithm which allows for continuously changing resampling ratio has been presented. The proposed implementation is based on a variable fractional delay filter which is implemented by means of a Farrow structure. Coefficients of this structure are computed on the basis of fractional delay filters which are designed using the offset window method. The proposed approach allows us to freely change the instantaneous resampling ratio during processing. Using such an algorithm we can simulate recording of audio on magnetic tape with nonuniform velocity as well as remove such distortions. We have demonstrated capabilities of the proposed approach based on the example of speech signal processing with a resampling ratio which was computed on the basis of estimated fundamental frequency of voiced speech segments.
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Abstract

In this article I will attempt to answer the question of why systemic solutions to (social) problems of Polish economic migrants fail to be instituted in Poland by means of social negotiations. Therefore, while emphasising the social dimension of Polish migration, I briefly present its specificity and point to some associated threats. Referring to the category labelled as social problem, I demonstrate the nature of obstacles which prevent a debate on Polish migration in the area of social negotiations from taking root on public ground in Poland. I also refer to the mechanisms of degradation of the public sphere as those which are preventing the development of systemic solutions to the problems of Polish migrant workers by means of social negotiations.
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Abstract

On the basis of hydrogen peroxide decomposition process occurring in the bioreactor with fixed-bed of commercial catalase the optimal feed temperature was determined. This feed temperature was obtained by maximizing the time-average substrate conversion under constant feed flow rate and temperature constraints. In calculations, convection-diffusion-reaction immobilized enzyme fixed-bed bioreactor described by a coupled mass and energy balances as well as general kinetic equation for rate of enzyme deactivation was taken into consideration. This model is based on kinetic, hydrodynamic and mass-transfer parameters estimated in earlier work. The simulation showed that in the biotransformation with thermal deactivation of catalase optimal feed temperature is only affected by kinetic parameters for enzyme deactivation and decreases with increasing value of activation energy for deactivation. When catalase undergoes parallel deactivation the optimal feed temperature is strongly dependent on hydrogen peroxide feed concentration, feed flow rate and diffusional resistances expressed by biocatalyst effectiveness factor. It has been shown that the more significant diffusional resistances and the higher hydrogen peroxide conversions, the higher the optimal feed temperature is expected.
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Abstract

Optimal feed temperature was determined for a non-isothermal fixed-bed reactor performing hydrogen peroxide decomposition by immobilized Terminox Ultra catalase. This feed temperature was obtained by maximizing the average substrate conversion under constant feed flow rate and temperature constraints. In calculations, convection-diffusion-reaction immobilized enzyme fixed-bed reactor described by a set of partial differential equations was taken into account. It was based on kinetic, hydrodynamic and mass transfer parameters previously obtained in the process of H2O2 decomposition. The simulation showed the optimal feed temperature to be strongly dependent on hydrogen peroxide concentration, feed flow rate and diffusional resistances expressed by biocatalyst effectiveness factor.
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Abstract

Wind energy has achieved prominence in renewable energy production. There fore, it is necessary to develop a diagnosis system and fault-tolerant control to protect the system and to prevent unscheduled shutdowns. The presented study aims to provide an experimental analysis of a speed sensor fault by hybrid active fault-tolerant control (AFTC) for a wind energy conversion system (WECS) based on a permanent magnet synchronous generator (PMSG). The hybrid AFTC switches between a traditional controller based on proportional integral (PI) controllers under normal conditions and a robust backstepping controller system without a speed sensor to avoid any deterioration caused by the sensor fault. A sliding mode observer is used to estimate the PMSG rotor position. The proposed controller architecture can be designed for performance and robustness separately. Finally, the proposed methodwas successfully tested in an experimental set up using a dSPACE 1104 platform. In this experimental system, the wind turbine with a generator connection via a mechanical gear is emulated by a PMSM engine with controled speed through a voltage inverter. The obtained experimental results show clearly that the proposed method is able to guarantee service production continuity for the WECS in adequate transition.
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Abstract

In this paper the capacity of non-uniform sampling rate conversion techniques, involving different interpolation methods, aimed at wow defect reduction, is examined. Involved are: linear interpolation, four polynomial-based interpolation methods and the windowed sincbased method. The examined polynomial methods are: Lagrange interpolation, polynomial fitting with additional noise reduction, Hermitan and Spline. The performance of an artificially distorted audio signal, restored using non-uniform resampling, is evaluated on the basis of standard audio defect measurement criteria and compared for all of the aforementioned interpolation methods. The chosen defect descriptors are: total harmonic distortion, total harmonic distortion plus noise and signal to noise ratio.
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Abstract

The work presents a structural and functional model of a distributed low level radio frequency (LLRF) control, diagnostic and telemetric system for a large industrial object. An example of system implementation is the European TESLA-XFEL accelerator. The free electron laser is expected to work in the VUV region now and in the range of X-rays in the future. The design of a system based on the FPGA circuits and multi-gigabit optical network is discussed. The system design approach is fully parametric. The major emphasis is put on the methods of the functional and hardware concentration to use fully both: a very big transmission capacity of the optical fiber telemetric channels and very big processing power of the latest series of DSP/PC enhanced and optical I/O equipped, FPGA chips. The subject of the work is the design of a universal, laboratory module of the LLRF sub-system. The current parameters of the system model, under the design, are presented. The considerations are shown on the background of the system application in the hostile industrial environment. The work is a digest of a few development threads of the hybrid, optoelectronic, telemetric networks (HOTN). In particular, the outline of construction theory of HOTN node was presented as well as the technology of complex, modular, multilayer HOTN system PCBs. The PCBs contain critical sub-systems of the node and the network. The presented exemplary sub-systems are: fast optical data transmission of 2.5 Gbit/s, 3.125 Gbit/s and 10 Gbit/s; fast A/C and C/A multichannel data conversion managed by FPGA chip (40 MHz, 65 MHz, 105 MHz), data and functionality concentration, integration of floating point calculations in the DSP units of FPGA circuit, using now discrete and next integrated PC chip with embedded OS; optical distributed timing system of phase reference; and 1GbEth video interface (over UTP or FX) for CCD telemetry and monitoring. The data and functions concentration in the HOTN node is necessary to make efficient use of the multigigabit optical fiber transmission and increasing the processing power of the FPGA/DSP/PC chips with optical I/O interfaces. The experiences with the development of the new generation of HOTN node based on the new technologies of data and functions concentration are extremely promising, because such systems are less expensive and require less labour.
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