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Wyniki wyszukiwania dla: FREE FLOW SPEED
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Graphene field-effect transistor application for flow sensing
PublikacjaMicroflow sensors offer great potential for applications in microfluidics and lab-on-a-chip systems. However, thermal-based sensors, which are commonly used in modern flow sensing technology, are mainly made of materials with positive temperature coefficients (PTC) and suffer from a self-heating effect and slow response time. Therefore, the design of novel devices and careful selection of materials are required to improve the overall...
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A numerical and experimental analysis of multi-hole orifice in turbulent flow
PublikacjaIn this research study, the comprehensive metrological analysis is investigated for a 4-hole orifice with module m = 0.25 installed in the pipeline with an internal diameter of 50 mm. A detailed numerical simulation was performed for the turbulence models: k-ε-realizable and k-ω-BSL. The novelties of the research include model validation by comparing the results of numerical studies with the experiment conducted in the area of...
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Speed sensorless ac drive with inverter output filter and fault detection using load torque signal
PublikacjaIn this paper, a sensorless induction motor (IM) drive using speed observer system is presented. The system includes load torque computation for gear fault detection. Nonlinear control method is adopted for controlling the motor over a wide speed range. An LC filter for smoothing current and voltage waveforms is used at the output of the voltage inverter. The use of filter imposes more building of the used observer to avoid using...
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Free trade with the former COMECON Countries as Unequal Exchange
PublikacjaTwo authors of this chapter were born to the East of what was once The Iron Curtain and two to the West. From both angles, the two systems – capitalism and communism – seemed to be as contrary to each other as possible. Few people are aware that in terms of industrial and trade policy, both classical capitalism and communism had a common root in the theories of German economist Friedrich List (1789-1846) (List, 1841). In fact,...
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Estimation of the steam condensation flow via CFD methods
PublikacjaThe results of numerical simulations to predict the performance of different steam models have been presented. All of the considered models of steam condensation have been validated on the base of benchmark experiment employing expansion in nozzle and next on the low pressure part of the steam turbine stage. For numerical analysis three models have been finally used – the ideal steam model without condensation, an equilibrium steam...
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Centrally Pivoted Tilting Pad Thrust Bearing with Carbon-Based Coated Collar—Experimental Results of Low- and Medium-Speed Operation
PublikacjaExperimental results of the research on a tilting pad thrust bearing with symmetrical pad support in the conditions of high loads and low speeds are presented in the paper. As described in the literature review, experimental results of tilting pad bearings at low speed/high load regime and transient conditions are rare. Unusual material selection - steel pad against a DLC-type coating on the collar was utilized. Such material combination...
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Experimental Investigations On The Momentum Pressure Drop During Flow Boiling Of R134a
PublikacjaThe article presents experimental investigations of the pressure drop during twophase flow. Experiments were performed for both adiabatic and heated flow of R134a. Obtained flow patterns were compared with the literature. Obtained data is used to validate momentum pressure drop predictions, a set of graphs showing comparisons, for a representative set of experimental conditions, of the two-phase frictional pressure gradients for...
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On the differential effect of temperature on the Nusselt-Rayleigh relationship in free convection
PublikacjaThe aim of and inspiration behind this paper was to explain the reasons, also observed by other researchers, of the discrepancy in the results of experimental free convection, which for small Rayleigh and Nusselt numbers in the initial phase of research can sometimes reach several hundred percent. These discrepancies decrease with increasing heating power and plate surface temperature, in proportion to the increase in Ra and Nu,...
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What matters most to patients? On the Core Determinants of Patient Experience from Free Text Feedback
PublikacjaFree-text feedback from patients is increasingly used for improving the quality of healthcare services and systems. A major reason for the growing interest in harnessing free-text feedback is the belief that it provides richer information about what patients want and care about. The use of computational approaches such as structural topic modelling for analysing large unstructured textual data such as free-text feedback from patients...
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The Effect of Sterols on Amphotericin B Self-Aggregation in a Lipid Bilayer as Revealed by Free Energy Simulations
PublikacjaAmphotericin B (AmB) is an effective but toxic antifungal drug, known to increase the permeability of the cell membrane, presumably by assembling into transmembrane pores in a sterol-dependent manner. The aggregation of AmB molecules in a phospholipid bilayer is, thus, crucial for the drug’s activity. To provide an insight into the molecular nature of this process, here, we report an atomistic molecular dynamics simulation study...
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Determination of Mechanical Energy Loss in Steady Flow by Means of Dissipation Power
PublikacjaWhen systems of simple geometry like pipes or regular channels are considered, the mechan- ical energy loss of the fluid flow can be expressed by local and longitudinal empirical energy loss coefficients. However, in the case of large spatially distributed objects, there are no simple approaches to this task. In practice, general recommendations addressing different types of objects are used, but they usually provide very coarse...
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Application of ANN and PCA to two-phase flow evaluation using radioisotopes
PublikacjaIn the two-phase flow measurements a method involving the absorption of gamma radiation can be applied among others. Analysis of the signals from the scintillation probes can be used to determine the number of flow parameters and to recognize flow structure. Three types of flow regimes as plug, bubble, and transitional plug – bubble flows were considered in this work. The article shows how features of the signals in the time and...
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Analytical Steady-State Model of the Pipeline Flow Process
PublikacjaThe paper addresses the issue of modeling the flow process in transmission pipelines. A base model used for numerical simulation is introduced. Under certain assumptions concerning steady state analysis, the differential equations describing the process are solved analytically for two cases: zero and nonzero inclination angle α. These equations describe a constant flow rate and a corresponding distribution of the pressure along...
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Free convection of water-Al2O3 nanofluid from horizontal porous coated tube
PublikacjaNanofluids are expected to enhance heat transfer in many thermal systems. Present efforts are concentrated on boiling heat transfer of nanofluids, although single phase convection is of key importance in various appliances such as car radiators or heating systems. This paper presents experimental results of heat transfer during free convection of water-Al3O3 nanofluid from horizontal tube covered with metallic porous coating. Contrary...
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Implementation of high-speed data transmission technological demonstrator using software defined radio technology
PublikacjaIn the article implementation of high-speed data transmission technological demonstrator using software defined radio technology is presented. A system architecture design including asymmetric framing transmission organization, which differs from the ones used in cellular systems is described. The construction of technological demonstrator consisting of management unit, radio unit and programmable multithreaded software performing...
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Accuracy, Memory and Speed Strategies in GPU-based Finite-Element Matrix-Generation
PublikacjaThis paper presents strategies on how to optimize GPU-based finite-element matrix-generation that occurs in the finite-element method (FEM) using higher order curvilinear elements. The goal of the optimization is to increase the speed of evaluation and assembly of large finite-element matrices on a single GPU (Graphics Processing Unit) while maintaining the accuracy of numerical integration at the desired level. For this reason,...
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Suppression of distortions in signals received from Doppler sensor for vehicle speed measurement
PublikacjaDoppler sensors are commonly used for movement detection and speed measurement. However, electromagnetic interference and imperfections in sensor construction result in degradation of the signal to noise ratio. As a result, detection of signals reflected from moving objects becomes problematic. The paper proposes an algorithm for reduction of distortions and noise in the signal received from a simple, dual-channel type of a Doppler...
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Implementation of high-speed data transmission technological demonstrator using software defined radio technology
PublikacjaIn the article implementation of a high-speed data transmission technological demonstrator using software defined radio technology is presented. A system architecture design including asymmetric framing transmission organization, which differs from the ones used in cellular systems is described. The construction of technological demonstrator consisting of a management unit, radio unit and programmable multi-threaded software performing...
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Analysis of the radiation dose in UV-disinfection flow reactors.
PublikacjaTheoretical considerations devoted to the variation of UV radiation doses in flow disinfection reactors are presented. The minimal time required by the fluid to pass the reactor was determined and combined with the radiation intensity. The active zones of the reactor were determined.
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Materials for Mediator-free Electron Transfer in the Enzymatic Electrodes of Biobatteries and Biofuel Cells
PublikacjaWe present functionalization of single-walled carbon nanotubes (SWCNTs) and their application in the enzymatic fuel cells construction. SWCNTs were covalently modified with different types of aromatic moieties. Free radical reaction was employed to create direct carbon-carbon bond between moiety and SWCNTs. In second approach functionalization takes place through amide bonding. Functionalized SWCNTs were characterized by spectroscopy...
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On various modelling approaches to real-time visualisation of blood flow
PublikacjaThis paper reviews various modelling approaches to real-time visualisation of blood flow. These include classic, macroscale approach based on the momentum conservation equation together with a proper constitutive equation. Moreover, modern micro- and mesoscale approaches, such as molecular dynamics and dissipative particle dynamics, are discussed. Advantages and disadvantages of the discussed methods are highlighted with particular...
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Novel adaptive flux observer for wide speed range sensorless control of induction motor
PublikacjaA new adaptive flux observer of induction motor is presented in the paper. The Lyapunov theory is utilized for derivation of the adaptation law of rotor flux angular speed, which acts as unknown parameter in an augmented induction motor model. In the field weakening region, where stray fluxes are comparable with rotor flux magnitude, the air-gap flux stabilization is proposed. An air-gap flux multiscalar model is derived for stator...
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Application of spatial neural simulators of turbine blade rows to fluid flow diagnostics
PublikacjaThis chapter presents the results of neural modelling of fluid flow in steam turbine row. In modelling working conditions of the flow channel varied, thus the aim of the work was to reconstruct the reference state - distributions of velocity, pressure, and losses in flow channel - with high accuracy for fluid flow diagnostics.
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Evaluation of the structures size in the liquid-gas flow by gamma-ray absorption
PublikacjaThe rapid development of tomography methods particularly electrical, X and gamma rays allows for a wide range of the information about flow structure. However, all of such methods are quite complicated. At the same time much simpler systems as the measuring system of gamma rays absorption, allows to obtain a all key flow information which describe the two-phase flow. In the article the results of analyzes of radiometric signal...
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Analysis of different tillage implements with respect to reduced fuel consumption, tractor operating speed and its wheel slippage
PublikacjaNowadays the prices of agricultural farm produced products are increasing with ant-speed and the prices of input for raising crops are increasing with rocket-speed. Therefore, there is a dire need to conduct some important studies to innovate the techniques which can lower the costs of crop production. In this context, this study was conducted to evaluate the consumption of fuel at different tillage implements, tractor operating...
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Influence of the Tool Rotational Speed on Physical and Chemical Properties of Dissimilar Friction-Stir-Welded AA5083/AA6060 Joints
PublikacjaAluminum alloys have been successfully used in the railroad and automotive industries because of their potential to significantly reduce component weights, and their good mechanical and anti-corrosion properties. Problems with joining aluminum alloys are characterized by low weldability, which influences the need for studies focused on unconventional methods. The environmentally friendly and low-cost friction-stir-welding method...
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Metrological analysis of an computerized system of protection against electric shock in circuits with variable speed drives
PublikacjaDrive systems, that can be operated at variable speed, are equipped with power electronics converters. This causes distortion of the earth current, and consequently the need to take into account the use of proper protective devices in relation to earth current harmonics. This paper presents a system for protection against electric shock in circuits with power electronics converters and metrological analysis indicating the requirements...
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Flow Process Models for Pipeline Diagnosis
PublikacjaThis chapter examines the problem of modeling and parameterization of the transmission pipeline flow process. First, the base model for discrete time is presented, which is a reference for other developed models. Then, the diagonal approximation (AMDA) method is proposed, in which the tridiagonal sub-matrices of the recombination matrix are approximated by their diagonal counterparts, which allows for a simple determination of...
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Comparison of various flow maldistribution quantification methods in mini heat exchangers
PublikacjaThe aim of study is to compare various flow maldistribution quantification methods, using velocity, mass flow rate, pressure, and temperature. An experimentally validated numerical study has been prepared and a heat exchanger with 34 semi-circular channels with a diameter of 3.1 mm has been tested. The minichannels were heated from the bottom with a heat flux of 50, 60, 70, and 80 kW/m2. The cases for various inlet velocities of...
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Alternative convolution approach to friction in unsteady pipe flow
PublikacjaIn the paper some aspects of the unsteady friction in pipe flow expressed by the convolution are analyzed. This additional term introduced into the motion equation involves the accelerations of fluid occurring in the past and a weighting function. The essence of such approach is to assume the appropriate form of weighting function. However, until now no fully reliable formula for this function has been found. To avoid some inconveniences...
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Air flow phenomena in the model of the blind drift
PublikacjaIn the presented paper, Particle Image Velocimetry (PIV) has been used to investigate flow pattern and turbulent structure in the model of blind drift. The presented model exist in mining, and has been analyzed to resolve ventilation issues. Blind region is particularly susceptible to unsafe methane accumulation. The measurement system allows us to evaluate all components of the velocity vector in channel cross-section simultaneously....
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Experimental investigations on condensation in flow of HFE-7100 in small diameter channels
PublikacjaIn the paper the authors present investigations of flow condensation with the use of the HFE-7100 as a working fluid. The original and new approach to removing the heat from the channel was applied. The research was carried out using a wide-range real time observations, e.g. using infrared camera and stroboscope microphotography. This paper presents the details of experiment as well as the influence of heat and flow parameters...
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Electronic structure and magnetism of samarium and neodymium adatoms on free-standing graphene
PublikacjaThe electronic structure of selected rare-earth atoms adsorbed on a free-standing graphene was investigated using methods beyond the conventional density functional theory (DFT+U, DFT +HIA, and DFT+ED). The influence of the electron correlations and the spin-orbit coupling on the magnetic properties has been examined. The DFT+U method predicts both atoms to carry local magnetic moments (spin and orbital) contrary to a nonmagnetic...
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Experimental investigation of free convection of glycol-Al2O3 nanofluid from horizontal tube
PublikacjaNanofluids came to be seen as a new generation of coolants, both in single- and two phase systems. Furthermore, nanofluids or nanocomposites may be used as a media in a thermal energy storage (TES) in such systems as sensible heat storage (SHS) and phase change materials (PCM). In the SHS systems the dominating mechanism of the heat transfer is natural convection. However, in the literature only a few investigations of free convection...
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EXPERIMENTAL INVESTIGATION OF FREE CONVECTION OF GLYCOL-Al2O3 NANOFLUID FROM HORIZONTAL TUBE
PublikacjaNanofluids came to be seen as a new generation of coolants, both in single- and two phase systems. Furthermore, nanofluids or nanocomposites may be used as a media in a thermal energy storage (TES) in such systems as sensible heat storage (SHS) and phase change materials (PCM). In the SHS systems the dominating mechanism of the heat transfer is natural convection. However, in the literature only a few investigations of free convection...
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Discrete-continuous optimisation of an axial flow blood pump
PublikacjaThis paper presents results of discrete-continuous optimisation of an axial flow blood pump. Evolution Strategies (ES) are used as a global optimisation method in order to localise the optimal solution in relatively short time. The whole optimisation process is fully automated. This also applies to geometry modelling. Numerical simulations of the flow inside the pump is performed by means of the Reynolds-Average Navier-Stokes...
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Experimental validation of pressure drop models during flow boiling of R134a – effect of flow acceleration and entrainment
PublikacjaA crucial step to assure proficient work of power and process apparatus is their proper design. A wide array of those devices operates within boiling or condensation of the working fluid to benefit from high heat transfer rates. Two-phase flows are associated with high heat transfer coefficients because of the latent heat of evaporation and high turbulence level between the liquid and the solid surface. Predicting heat transfer...
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Computational issues of solving the 1D steady gradually varied flow equation
PublikacjaIn this paper a problem of multiple solutions of steady gradually varied flow equation in the form of the ordinary differential energy equation is discussed from the viewpoint of its numerical solution. Using the Lipschitz theorem dealing with the uniqueness of solution of an initial value problem for the ordinary differential equation it was shown that the steady gradually varied flow equation can have more than one solution....
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Alternative Approach to Convolution Term of Viscoelasticity in Equations of Unsteady Pipe Flow
PublikacjaIn the paper the selected aspects concerning description of viscoelastic behavior of pipe walls during unsteady flow are analyzed. The alternative convolution expression of the viscoelastic term is presented and compared with the corresponding term referring to unsteady friction. Both approaches indicate similarities in the forms of impulse response functions and the parameter properties. The flow memory was introduced into convolution...
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Simplified Numerical Model for Transient Flow of Slurries at Low Concentration
PublikacjaRapid transients are particularly dangerous in industrial hydro-transport systems, where solid-liquid mixtures are transported via long pressure pipelines. A mathematical description of such flow is difficult due to the complexity of phenomena and difficulties in determining parameters. The main aim of the study was to examine the influence of the simplified mixture density and wave celerity description on satisfactory reproduction...
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Adaptive traffic optimization using Variable Speed Limits; Adaptacyjna optymalizacja ruchu drogowego przy pomocy zmiennych ograniczeń prędkości
PublikacjaVariable speed limits (VSL) is an intelligent transportation system (ITS) solution for traffic management. The speed limits can be changed dynamically in order to adapt to traffic, weather, or road surface conditions. This paper presents an approach for such an adaptive traffic control where the primary goal is to ensure traffic safety and efficiency of the traffic control system (fast response to dynamically changing traffic,...
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Pollutants removal effectiveness in hydrophyte filters with sequential vertical and horizontal flow
PublikacjaThe object of investigations was the constructed wetland in Wiedersberg in Saxonia in Germany supplied with domestic sewage from 145 inhabitants. The biological part was composed of sequential reed beds with vertical and horizontal flow of sewage. It in one of new solutions, because up till now configuration with vertical bed situated at front of biological part of treatment was applied.The evaluation of object performance was...
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A New Approach for the Mitigating of Flow Maldistribution in Parallel Microchannel Heat Sink
PublikacjaThe problem of flow maldistribution is very critical in microchannel heat sinks (MCHS). It induces temperature nonuniformity, which may ultimately lead to the breakdown of associated system. In the present communication, a novel approach for the mitigation of flow maldistribution problem in parallel MCHS has been proposed using variable width microchannels. Numerical simulation of copper made parallel MCHS consisting of 25 channels...
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Hysteresis curves for some periodic and aperiodic perturbations in magnetosonic flow
PublikacjaA thermodynamic relation between perturbations of pressure and mass density in the magnetohydrodynamic flow is theoretically studied. Planar magnetohydrodynamic perturbations with the wave vector, which forms a constant angle with the equilibrium magnetic field, are under study. The theory considers thermal conduction of a plasma and the deviation from adiabaticity of a flow due to some kind of heating–cooling function. It also...
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Cylindrical orifice testing in laminar flow with the orifice diameter ratio β = 0.5
PublikacjaThe paper presents the results of an experimental study of a cylindrical orifice with the orifice diameter ratio β = 0.5 and the flow opening length‑to‑diameter ratio L/d = 1, with hydraulic oil flowing in the DN50 measuring channel. The measurements of the values characterising the oil flow were made in the laminar flow regime, for the Reynolds numbers ranging between Re = 100 to 950. Based on the experimental tests, standard...
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Effect of pine impregnation and feed speed on sound level and cutting power in wood sawing
PublikacjaThe sound levels along with the cutting power registered during the sawing process of the impregnated and non-impregnated pine wood at two feed speeds are shown and compared in this paper. Statistically significant differences in the acoustic signals occurred at the lower feed rate. The differences became smaller with an increase in the feed speed. In contrast to the sound signal, the differences...
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Optimization of the spindle speed during milling of large-sized structures with the use of technique of Experiment-Aided Virtual Prototyping
PublikacjaIn the paper are presented considerations concerning vibration suppression problems during milling of large-sized workpieces with the use of innovative method of matching the spindle speed of cutting tool. It depends on repeatable change of the spindle speed value as soon as the optimal vibration state of the workpiece approaches. The values of dominant “peaks” in the frequency spectra and the Root Mean Square (RMS) values of time...
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Frequency characteristics of induction machine speed observers
PublikacjaWłaściwości napędu bezczujnikowego z silnikiem indukcyjnym zależą od struktury obserwatora prędkości. System ten wymaga starannej analizy w przypadku uszkodzenia maszyny, której celem jest odpowiedź na pytania: jak układ regulacji pracuje przy niesymetrii maszyny spowodowanej np. uszkodzeniem klatki wirnika oraz jak obserwator odtwarza pulsacje prędkości spowodowane niesymetrią maszyny. W artykule przedstawiono charakterystyki...
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Changes in the speed of ants as a result of aggressive interactions
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High-speed memoryless binary/residue converter
PublikacjaW pracy zaprezentowano nowy szybki konwerter z systemu binarnego do systemu resztowego dla liczb o zakresie do 60 bitów. W konwerterze stosowane są wyłącznie układy kombinacyjne. Algorytm konwertera oparty jest na dodawaniu niezerowych cyfr binarnych reprezentacji kolejnych potęg 2 modulo m. Dodawanie jest realizowane przy użyciu wielooperandowego sumatora CSA oraz sumatora CPA. Suma wyjściowa CPA jest redukowana do zakresu 2m-1...