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Number of results: 246
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Abstract

The aim of this article is to present the results of research aimed at confirmation whether it is possible to form an intermediate band in GaAs implantation with H+ ions. The obtained results were discussed with particular emphasis on possible applications in the photovoltaic industry. As it is commonly known, the idea of intermediate band solar cells reveals considerable potential as the most fundamental principle of the next generation of semiconductors solar cells. In progress of the research, a series of GaAs samples were subjected to poly-energy implantation of H+ ions, followed by high-temperature annealing. Tests were conducted using thermal admittance spectroscopy, under conditions of variable ambient temperature, measuring signal frequency in order to localize deep energy levels, introduced by ion implantation. Activation energy ΔE was determined for additional energy levels resulting from the implantation of H+ ions. The method of determining the activation energy value is shown in Fig. 2 and the values read from it are #27;0 = 10��9 (Ω#1;cm)��1 for 1000=T0 = 3:75 K��1 and #27;1 = 1:34 #2; 10��4 (Ω#1;cm)��1 for 1000=T1 = 2:0 K��1. As a result, we obtain ΔE #25; 0:58 eV. It was possible to identify a single deep level in the sample of GaAs implanted with H+ ions. Subsequently, its location in the band gap was determined by estimating the value of ΔE. However, in order to confirm whether the intermediate band was actually formed, it is necessary to perform further analyses. In particular, it is necessary to implement a new analytical model, which takes into consideration the phenomena associated with the thermally activated mechanisms of carrier transport as it was described in [13]. Moreover, the influence of certain parameters of ion implantation, post-implantation treatment and testing conditions should also be considered.
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Abstract

The main points of the UPoN-2018 talk and some valuable comments from the Audience are briefly summarized. The talk surveyed the major issues with the notion of zero-point thermal noise in resistors and its visibility; moreover it gave some new arguments. The new arguments support the old view of Kleen that the known measurement data “showing” zero-point Johnson noise are instrumental artifacts caused by the energy-time uncertainty principle. We pointed out that, during the spectral analysis of blackbody radiation, another uncertainty principle is relevant, that is, the location-momentum uncertainty principle that causes only the widening of spectral lines instead of the zero-point noise artifact. This is the reason why the Planck formula is correctly confirmed by the blackbody radiation experiments. Finally a conjecture about the zero-point noise spectrum of wide-band amplifiers is shown, but that is yet to be tested experimentally.
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Abstract

Gas-liquid flows abound in a great variety of industrial processes. Correct recognition of the regimes of a gasliquid flow is one of the most formidable challenges in multiphase flow measurement. Here we put forward a novel approach to the classification of gas-liquid flow patterns. In this method a flow-pattern map is constructed based on the average energy of intrinsic mode function and the volumetric void fraction of gas-liquid mixture. The intrinsic mode function is extracted from the pressure fluctuation across a bluff body using the empirical mode decomposition technique. Experiments adopting air and water as the working fluids are conducted in the bubble, plug, slug, and annular flow patterns at ambient temperature and atmospheric pressure. Verification tests indicate that the identification rate of the flow-pattern map developed exceeds 90%. This approach is appropriate for the gas-liquid flow pattern identification in practical applications.
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Abstract

To find effective and practical methods to distinguish gas-liquid two-phase flow patterns, new flow pattern maps are established using the differential pressure through a classical Venturi tube. The differential pressure signal was first decomposed adaptively into a series of intrinsic mode functions (IMFs) by the ensemble empirical mode decomposition. Hilbert marginal spectra of the IMFs showed that the flow patterns are related to the amplitude of the pressure fluctuation. The cross-correlation method was employed to sift the characteristic IMF, and then the energy ratio of the characteristic IMF to the raw signal was proposed to construct flow pattern maps with the volumetric void fraction and with the two-phase Reynolds number, respectively. The identification rates of these two maps are verified to be 91.18% and 92.65%. This approach provides a cost-effective solution to the difficult problem of identifying gas-liquid flow patterns in the industrial field.
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Abstract

Quality of energy produced in renewable energy systems has to be at the high level specified by respective standards and directives. One of the most important factors affecting quality is the estimation accuracy of grid signal parameters. This paper presents a method of a very fast and accurate amplitude and phase grid signal estimation using the Fast Fourier Transform procedure and maximum decay side-lobes windows. The most important features of the method are elimination of the impact associated with the conjugate’s component on the results and its straightforward implementation. Moreover, the measurement time is very short ‒ even far less than one period of the grid signal. The influence of harmonics on the results is reduced by using a bandpass pre-filter. Even using a 40 dB FIR pre-filter for the grid signal with THD ≈ 38%, SNR ≈ 53 dB and a 20‒30% slow decay exponential drift the maximum estimation errors in a real-time DSP system for 512 samples are approximately 1% for the amplitude and approximately 8.5・10‒2 rad for the phase, respectively. The errors are smaller by several orders of magnitude with using more accurate pre-filters.
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Abstract

This paper contains the full way of implementing a user-defined hyperelastic constitutive model into the finite element method (FEM) through defining an appropriate elasticity tensor. The Knowles stored-energy potential has been chosen to illustrate the implementation, as this particular potential function proved to be very effective in modeling nonlinear elasticity within moderate deformations. Thus, the Knowles stored-energy potential allows for appropriate modeling of thermoplastics, resins, polymeric composites and living tissues, such as bone for example. The decoupling of volumetric and isochoric behavior within a hyperelastic constitutive equation has been extensively discussed. An analytical elasticity tensor, corresponding to the Knowles stored-energy potential, has been derived. To the best of author's knowledge, this tensor has not been presented in the literature yet. The way of deriving analytical elasticity tensors for hyperelastic materials has been discussed in detail. The analytical elasticity tensor may be further used to develop visco-hyperelastic, nonlinear viscoelastic or viscoplastic constitutive models. A FORTRAN 77 code has been written in order to implement the Knowles hyperelastic model into a FEM system. The performace of the developed code is examined using an exemplary problem.
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Abstract

Oxy-fuel combustion (OFC) belongs to one of the three commonly known clean coal technologies for power generation sector and other industry sectors responsible for CO2emissions (e.g., steel or cement production). The OFC capture technology is based on using high-purity oxygen in the combustion process instead of atmospheric air. Therefore flue gases have a high concentration of CO2- Due to the limited adiabatic temperature of combustion some part of CO2must be recycled to the boiler in order to maintain a proper flame temperature. An integrated oxy-fuel combustion power plant constitutes a system consisting of the following technological modules: boiler, steam cycle, air separation unit, cooling water and water treatment system, flue gas quality control system and CO2processing unit. Due to the interconnections between technological modules, energy, exergy and ecological analyses require a system approach. The paper present the system approach based on the 'input-output' method to the analysis of the: direct energy and material consumption, cumulative energy and exergy consumption, system (local and cumulative) exergy losses, and thermoecological cost. Other measures like cumulative degree of perfection or index of sustainable development are also proposed. The paper presents a complex example of the system analysis (from direct energy consumption to thermoecological cost) of an advanced integrated OFC power plant.
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Abstract

The paper deals with the properties and microstructure of Reactive Powder Concrete (RPC), which was developed at Cracow University of Technology. The influence of three different curing conditions: water (W), steam (S) and autoclave (A) and also steel fibres content on selected properties of RPC was analyzed. The composite characterized by w/s ratio equal to 0.20 and silica fume to cement ratio 20%, depending on curing conditions and fibres content, obtained compressive strength was in the range from 200 to 315 MPa, while modulus of elasticity determined during compression was about 50 GPa. During three-point bending test load-deflection curves were registered. Base on aforementioned measurements following parameters were calculated: flexural strength, stress at limit of proportionality (LOP), stress at modulus of rapture (MOR), work of fracture (WF), and toughness indices I₅, I₁₀ and I₂₀. Both amount of steel fibres and curing conditions influence the deflection of RPC during bending.
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Abstract

This paper presents a design of a tracked in-pipe inspection mobile robot with an adaptive drive positioning system. The robot is intended to operate in circular and rectangular pipes and ducts, oriented horizontally and vertically. The paper covers a design process of a virtual prototype, focusing on track adaptation to work environment. A mathematical description of a kinematic model of the robot is presented. Operation of the prototype in pipes with a cross-section greater than 210 mm is described. Laboratory tests that validate the design and enable determination of energy consumption of the robot are presented.
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Abstract

Higher active power of a submerged arc furnace is commonly believed to increase its capacity in the process of ferrosilicon smelting. This is a true statement but only to a limited extent. For a given electrode diameter d, there is a certain limit value of the submerged arc furnace active power. When this value is exceeded, the furnace capacity in the process of ferrosilicon smelting does not increase but the energy loss is higher and the technical and economic indicators become worse. Maximum output regarding the reaction zone volumes is one of parameters that characterize similarities of furnaces with various geometrical parameters. It is proportional to d3 and does not depend on the furnace size. The results of statistical analysis of the ferrosilicon smelting process in the 20 MVA furnace have been presented. In addition to basic electrical parameters, such as active power and electrical load of the electrodes, factors contributing to higher resistance of the furnace bath and resulting lower reactive power Px demonstrate the most significant effect on the electrothermal process of ferrosilicon smelting. These parameters reflect metallurgical conditions of ferrosilicon smelting, such as the reducer fraction, position of the electrodes and temperature conditions of the reaction zones.
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Abstract

Development of open cellular metal foam technology based on investment casting applying the polyurethane pattern is discussed. Technological process comprises preparing of the ceramic mold applying PUR foam as the pattern, firing of the mold, pouring of the liquid Zn-Al alloy into the mold and washing out of the ceramic material from cellular casting. Critical parameters such as the temperature of mold and poured metal, design of gating system affected by metalostatic pressure allowed to produce castings with cellular structure characterized by the open porosity. Metal cellular foams with the open porosity embedded in phase change material (PCM) enhance heat transfer and reduce time operations in energy storage systems. Charging and discharging were performed at the laboratory accumulator by heating and cooling with flowing water characterized by the temperatures of 97-100oC. Temperature measurements were collected from 7 different thermocouples located in the accumulator. In relation to the tests with pure paraffin, embedding of the metal Zn-Al cellular foam in paraffin significantly decreases temperature gradients and melting time of paraffin applied as PCM characterized by the low thermal conductivity. Similarly, reduction of discharging time by this method improves the efficiency of thermal energy storage system applied in solar power plants or for the systems of energy efficient buildings.
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Abstract

This paper presents a load equivalent conductance based control method for a shunt active power filter. The principle of energy balance in the circuit, which means between supplying source - active filter - load, is used to obtain the control formula. The natural inertia of the active filter action is exploited, so no PI regulators are needed. The active filter can compensate for non-active current and, additionally, can stabilise the supplying source active power. In a case of generating loads energy harvesting is possible. The presented method is useful as well for voltage-source as current-source inverter based active filters, and for DC system as well as for AC single- or three-phase one.
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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

The paper presents the mathematical modelling of selected isothermal separation processes of gaseous mixtures, taking place in plants using membranes, in particular nonporous polymer membranes. The modelling concerns membrane modules consisting of two channels - the feeding and the permeate channels. Different shapes of the channels cross-section were taken into account. Consideration was given to co-current and counter-current flows, for feeding and permeate streams, respectively, flowing together with the inert gas receiving permeate. In the proposed mathematical model it was considered that pressure of gas changes along the length of flow channels was the result of both - the drop of pressure connected with flow resistance, and energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel. The literature on membrane technology takes into account only the drop of pressure connected with flow resistance. Consideration given to energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel constitute the essential novelty in the current study. The paper also presents results of calculations obtained by means of a computer program which used equations of the derived model. Physicochemical data concerning separation of the CO2/CH4 mixture with He as the sweep gas and data concerning properties of the membrane made of PDMS were assumed for calculations.
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Abstract

In the complex RLC network, apart from the currents flows arising from the normal laws of Kirchhoff, other distributions of current, resulting from certain optimization criteria, may also be received. This paper is the development of research on distribution that meets the condition of the minimum energy losses within the network called energy-optimal distribution. Optimal distribution is not reachable itself, but in order to trigger it off, it is necessary to introduce the control system in current-dependent voltage sources vector, entered into a mesh set of a complex RLC network. For energy-optimal controlling, to obtain the control operator, the inversion of R(s) operator is required. It is the matrix operator and the dispersive operator (it depends on frequency). Inversion of such operators is inconvenient because it is algorithmically complicated. To avoid this the operator R(s) is replaced by the R’ operator which is a matrix, but non-dispersive one (it does not depend on s). This type of control is called the suboptimal control. Therefore, it is important to make appropriate selection of the R’ operator and hence the suboptimal control. This article shows how to implement such control through the use of matrix operators of multiple differentiation or integration. The key aspect is the distribution of a single rational function H(s) in a series of ‘s’ or ‘s⁻¹’. The paper presents a new way of developing a given, stable rational transmittance with real coefficients in power series of ‘s/s⁻¹՚. The formulas to determine values of series coefficients (with ‘s/s⁻¹’) have been shown and the conditions for convergence of differential/integral operators given as series of ‘s/s⁻¹’ have been defined.
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Abstract

Many parts of remote locations in the world are not electrified even in this Advanced Technology Era. To provide electricity in such remote places renewable hybrid energy systems are very much suitable. In this paper PV/Wind/Battery Hybrid Power System (HPS) is considered to provide an economical and sustainable power to a remote load. HPS can supply the maximum power to the load at a particular operating point which is generally called as Maximum Power Point (MPP). Fuzzy Logic based MPPT (FLMPPT) control method has been implemented for both Solar and Wind Power Systems. FLMPPT control technique is implemented to generate the optimal reference voltage for the first stage of DC-DC Boost converter in both the PV and Wind energy system. The HPS is tested with variable solar irradiation, temperature, and wind speed. The FLMPPT method is compared with P&O MPPT method. The proposed method provides a good maximum power operation of the hybrid system at all operating conditions. In order to combine both sources, the DC bus voltage is made constant by employing PI Controllers for the second stage of DC-DC Buck-Boost converter in both Solar and Wind Power Systems. Battery Bank is used to store excess power from Renewable Energy Sources (RES) and to provide continuous power to load when the RES power is less than load power. A SPWM inverter is designed to convert DC power into AC to supply three phase load. An LC filter is also used at the output of inverter to get sinusoidal current from the PWM inverter. The entire system was modeled and simulated in Matlab/Simulink Environment. The results presented show the validation of the HPS design.
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Abstract

A contactless energy transmission system is essential to supply onboard systems of electromagnetically levitated vehicles without physical contact to the guide rail. One of the possibilities to realise a contactless power supply (CPS) is by integrating the primary actuator into the guide rail of an electromagnetic guiding system (MGS). The secondary actuator is mounted on the elevator car. During the energy transmission, load dependent non-linear losses occur in the guide rail. The additional losses, which are caused by the leakage flux penetrating into the guide rail, cannot be modelled using the classical approach of iron losses in the equivalent circuit of a transformer, which is a constant parallel resistance to the mutual inductance. This paper introduces an approach for modelling the load dependent non-linear losses occurring in the guide rail using additional variable discrete circuit elements.
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Abstract

This article has two outreach aims. It concisely summarizes the main research and technical efforts in the EC H2020 ARIES Integrating Activity – Accelerator Research and Innovation for European Science and Society [1] during the period 2017/2018. ARIES is a continuation of CARE, TIARA and EuCARD projects [2-3]. The article also tries to show these results as an encouragement for local physics and engineering, research and technical communities to participate actively in such important European projects. According to the author’s opinion this participation may be much bigger [4-27]. All the needed components to participate – human, material and infrastructural are there [4,7]. So why the results are not satisfying as they should be? The major research subjects of ARIES are: new methods of particles acceleration including laser, plasma and particle beam interactions, new materials and accelerator components, building new generations of accelerators, energy efficiency and management of large accelerator systems, innovative superconducting magnets, high field and ultra-high gradient magnets, cost lowering, system miniaturization, promotion of innovation originating from accelerator research, industrial applications, and societal implications. Two institutions from Poland participate in ARIES – these are Warsaw University of Technology and Institute of Nuclear Chemistry and Technology in Warsaw. There are not present some of the key institutes active in accelerator technology in Poland. Let this article be a small contribution why Poland, a country of such big research potential, contributes so modestly to the European accelerator infrastructural projects? The article bases on public and internal documents of ARIES project, including the EU Grant Agreement and P1 report. The views presented in the paper are only by the author and not necessarily by the ARIES.
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Abstract

Concentrations and elemental composition of fine (PM2.5) and coarse (PM2.5-10) ambient particles, at two sampling points located at the same urban background sites, were investigated. The points were 20 m distant from each other and at various heights (2 and 6 m) above the ground. A dichotomous sampler, equipped with a virtual impactor, and a cascade impactor were used to sample the dust. An X-ray fluorescence spectrometer was used in the elemental analyses. The investigations revealed heterogeneity of the spatial distribution and the elemental composition of suspended dust at the investigated urban background site. Coarse dust, whose concentration at 2.0 m above the ground was affected by secondary emission from roads, soil and other local low-level sources in some periods, appeared more heterogeneous.
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