Search
Filters
total: 42
Search results for: VARIATION COEFFICIENT
-
SFEM Analysis of Beams with Scaled Lengths including Spatially Varying and Cross-Correlated Concrete Properties
PublicationThis paper presents the results obtained for plain concrete beams under four-point bending with spatially varying material properties. Beams of increasing length but constant depth were analyzed using the stochastic finite element method. Spatial fluctuation of a uniaxial tensile strength, fracture energy and elastic modulus was defined within cross-correlated random fields. The symmetrical Gauss probability distribution function...
-
Prediction of flow boiling heat transfer coefficient for carbon dioxide in minichannels and conventional channels
PublicationIn the paper are presented the results of calculations using authors own model to predict heat transfer coefficient during flow boiling for carbon dioxide. The experimental data from various researches were scrutinised conducted for a full range of quality variation and wide range of mass velocity. The aim of the study was to test the sensitivity of the in-house model. The work shows the importance of taking into account surface...
-
Experimental study and comparison with predictive methods for flow boiling heat transfer coefficient of HFE7000
PublicationThis article describes an experimental study of flow boiling of HFE7000 inside a smooth vertical channel. The investigation has been carried out in a circular stainless-steel tube with an inner diameter of 2.3 mm. The data have been collected for the applied heat fluxes q ranging from 61 to 205 kW/m2, the mass flux G ranging from 214 to 1006 kg/(m2 s), the saturation temperature Tsat ranging from 30 to 54 °C and the full range...
-
Displacement Sensors Based on the Phase of the Reflection Coefficient of a Split Ring Resonator Loaded Transmission Line
Publication— In this paper, novel displacement sensors using a microstrip loaded with a pair of split ring resonators (SRRs) are proposed. It is shown that the phase of the reflection coefficient from the loading SRRs can be used for displacement sensing. The paper also proposes a differential version of the sensor that benefits from a higher sensitivity and reference zero, which is useful for alignment purposes. It is further shown that...
-
Prediction of flow boiling heat transfer coefficient for carbon dioxide in minichannels and conventional channels
PublicationIn the paper presented are the results of calculations using authors own model to predict heat transfer coefficient during flow boiling of carbon dioxide. The experimental data from various resea rches were collected. Calculations were conducted for a full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the in-house model. The results show the importance of taking into...
-
Wyznaczanie współczynnika przejmowania ciepła podczas wrzenia w przepływie dwutlenku węgla (Prediction of flow boling heat transfer coefficient for carbon dioxide in minichannels)
PublicationW pracy przedstawiono wyniki obliczeń uzyskane za pomocą własnego modelu półemirycznego dla wybranych danych eksperymentalnych dla wrzenia w przepływie dwutlenku węgla. Metoda obliczeniowa została zweryfikowana z danymi eksperymentalnymi Docoulombiera i innych (2011) oraz Mastrullo i innych (2009). Badania eksperymentalne dotyczą pełnego zakresu zmienności stopnia suchości oraz zakresu prędkości masowej G=200-1200 kg/m2s. rozwijany...
-
FE investigations of the effect of fluctuating local tensile strength on coupled energetic-statistical size effect in concrete beams
PublicationThe effect of fluctuating local tensile strength on a coupled energetic-statistical size effect in plain concrete beams under bending was numerically investigated. First, the influence of varying autocorrelation length of the random field describing a spatial variation of local tensile strength was studied. Next, the influence of the coefficient of variation of local tensile strength was analyzed. The numerical FE investigations...
-
Application of Headspace Solid-phase Microextraction with Poly(1-vinyl-3- Hexylimidazolium Chloride) Polymeric Ionic Liquid Coating using GC - MS to Determine Volatile Fatty Acids in Dairy Wastewater
PublicationVolatile fatty acids were determined in this study using headspace solid-phase microextraction (HS-SPME) with a poly(1-vinyl-3-hexylimidazolium chloride) polymeric ionic liquid coated fiber followed by gas chromatography - mass spectrometry. Experimental parameters such as extraction time and temperature, sample volume as well as desorption time and temperature were optimized. Detection limits of the method were in the range of...
-
Flow boiling intensification in minichannels by means of mechanical flow turbulising inserts
PublicationThe work presents the results of experimental investigation on heat transfer in minichannels. Refrigerant R123 was used as a test fluid. Single vertical silver tubes of 380 mm length and 2.3 mm diameter were examined with two variants of turbulising inserts. A wide range of parameters was considered, namely mass flux G=534-3011 kg/(m2s), heat flux qw=28.5-68.4 kW/m2, saturation temperature Tsat=23-86 stC and the full range of vapour...
-
Calculation method for flow boiling and flow condensation of R134a and R1234yf in conventional and small diameter channels
PublicationThe paper presents the results of calculations performed using the authors’ model to predict the heat transfer coefficient during flow boiling for two refrigerants R134a and R1234yf. The experimental data from various past studies have been collected and the calculations have been conducted for the full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the in-house...
-
EXPERIMENTAL VERIFICATION OF THE METHOD OF FLOW BOILING AND FLOW CONDENSATION HEAT TRANSFER PREDICTION FOR SELECTED FLUIDS
PublicationIn the paper presented are the results of calculations using authors own model to predict heat transfer coefficient during flow boiling of different refrigerants. The experimental data from various research studies from literature were collected. Calculations were conducted for a full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the in- house developed model....
-
Non-adiabatic Effects in Pressure Drop Calculations in Flow Boiling and Flow Condensation in Minichannels
PublicationConsiderations presented in the paper relate both to the case of flow boiling and flow condensation in conventional channels as well as small diameter ones. Authors devoted all the possible attention that the modeling presented is applicable to the whole range of quality variation in both cases of condensation and boiling. The form of two-phase flow multiplier, which is a major factor in modeling presented here, should be capable...
-
Ellipsometric study of carbon nitride films deposited by DC-magnetron sputtering
PublicationWe report the optical properties of a carbon nitride (CNx) film as a function of nitrogen concentration (N/C) of the deposited film. As nitrogen concentration is increased (N/C ratio) in a CNx film, the refractive index and band gap also increase. The real and imaginary parts, n and k (refractive index and extinction coefficient) of the complex refraction index of carbon nitride films were determined by spectroscopic ellipsometry...
-
The impact of material degradation on the resistance and reliability of truss structures
PublicationThe paper analyses limit load-carrying capacity and buckling load of truss towers used to support high voltage power lines. The analysed typical structure was subjected to characteristic loads and their combinations. The results were applied to assess structural resistance with regard to steel corrosion in the long-term operation. The extent of structural deterioration was assessed due to Young's modulus decrement in the course...
-
Partition of friction heat between sliding semispaces due to adhesion-deformational heat generation
PublicationAnalytical expressions of heat-partition coefficient and contact temperatures for two sliding semispaces with account for adhesion-deformational heat generation and contact heat exchange have been obtained. The rate of deformational heat generation is assumed to decay exponentially with increase of distance from the interface. It has been shown that heat-generation configuration and the intensity of contact heat exchange have impact...
-
Stability of trusses with linear elastic side-supports
PublicationThe present research is devoted to study of a lateral buckling of truss with linear elastic side supports. The elastic support reaction in relation to force in compressed chord and coefficient of buckling length related to side support distance are also calculated. The effect of slope of side support on limit force is also considered. The nonlinear analysis of two roof trusses are carried out. The results are compared to design...
-
Decoupled Kalman filter based identification of time-varying FIR systems
PublicationWhen system parameters vary at a fast rate, identification schemes based on model-free local estimation approaches do not yield satisfactory results. In cases like this, more sophisticated parameter tracking procedures must be used, based on explicit models of parameter variation (often referred to as hypermodels), either deterministic or stochastic. Kalman filter trackers, which belong to the second category, are seldom used in...
-
Statistics 2022_23
e-Learning Courses1.Elements of probability. The axioms of the probability theory 2. Random variables and their distributions. Discrete and continuous random variables 3. Parameters of random variables: expected value, moments 4. Selected distributions of random variables (Bernoulli, Poison, Gaussian) 5.The distribution in the sample. Visualisation by histograms 6. Measures of statistical location: arithmetic mean, median, quantiles. 7. Measures...
-
Comparison of predictive methods for flow boiling heat transfer in conventional channels and minichannels - the effect of reduced pressure
PublicationIn the paper are presented the results of follow on studies from [1]–[3] using authors own model to predict heat transfer coefficient during flow boiling. The model has been tested against a large selection of experimental data collected from various researchers to investigate the sensitivity of the in-house developed model. The collected experimental data came from various studies from literature and were conducted for the full...
-
Method of estimating the rolling resistance coefficient of vehicle tyre using the roller dynamometer
PublicationThe tendency in the past few years has been to introduce tyres with lower rolling resistance coefficients to the market. This paper presents a mathematical method for determining the rolling resistance coefficients variation depending on the speed. The method uses power balance which results from automobile dynamics while rolling on chassis dynamometer. The rolling resistance coefficients of tyres obtained through ‘drum test method’,...
-
Modelowanie procesu wrzenia i kondensacji w rozszerzonym zakresie ciśnień zredukowanych
PublicationNiniejsza rozprawa doktorska ma na celu pokazanie wpływu uwzględnienia ciśnienia zredukowanego w analizowanym modelu opisują-cym współczynnik przejmowania ciepła na zbieżność z danymi eksperymentalnymi.Przedmiotem analizy jest półempiryczny model Mikielewicza w zastosowaniu do danych eksperymentalnych w kanałach konwencjonalnych i o małej średnicy płynów uznanych za perspektywiczne.W ramach realizowanych prac badawczych pozyskano...
-
ECHOES REDUCTION DURING DIGITAL DATA TRANSMISSION IN HYDROACOUSTIC CHANNEL – LABORATORY EXPERIMENT
PublicationThe possibility of using a hydroacoustic channel for digital data transmission is very limited. This is due to the effect of multipath propagation of the emitted acoustic wave and the damping of the mechanical wave in this medium, which increase with frequency. The first of these phenomena results in inter-symbol interference disturbances in data transmission systems, including even hundreds of symbols. Due to the number of reflections...
-
Atomic-Scale Finite-Element Modeling of Elastic Mechanical Anisotropy in Finite-Sized Strained Phosphorene Nanoribbons
PublicationNanoribbons are crucial nanostructures due to their superior mechanical and electrical properties. This paper is devoted to hybrid studies of the elastic mechanical anisotropy of phosphorene nanoribbons whose edges connect the terminals of devices such as bridges. Fundamental mechanical properties, including Young’s modulus, Poisson’s ratio, and density, were estimated from first-principles calculations for 1-layer, 3-layer, and...
-
Eksperymentalna analiza współczynników oporów lokalnych dla wybranych kształtek i złączek w systemach rur wielowarstwowych
PublicationArtykuł poświęcony jest analizie wartości współczynników oporów lokalnych dla wybranych kształtek i złączek pracujących w instalacjach z rur wielowarstwowych z tworzyw sztucznych. Badaniom poddano elementy o średnicach DN16, DN20, DN25, powszechnie wykorzystywane we współczesnych instalacjach sanitarnych. W pracy przedstawiono wybrane wyniki badań laboratoryjnych (dla rozszerzeń, kolanek i trójników) oraz ich porównanie z wartościami...
-
INWESTYCJE ALTERNATYWNE – OPŁACALNOŚĆ A RYZYKO
PublicationW rozprawie określono pojęcie oraz miejsce inwestycji alternatywnych na rynku inwestycyjnym. Wskazane zostały atrybuty tych inwestycji. Zbudowano klasyfikację inwestycji alternatywnych w podziale na kategorie oraz typy wraz ze wskazaniem powiązań pomiędzy poszczególnymi produktami. Dokonano autorskiego podziału analizowanych inwestycji na aktywne i pasywne. Zbadano stopę zwrotu i ryzyko pięćdziesięciu inwestycji alternatywnych,...
-
Experimental and analytical thermal study of PTFE composite sliding against high carbon steel as a function of the surface roughness, sliding velocity and applied load
PublicationThis study investigates the contact temperatures caused by frictional heating of sliding parallel pairs. In this case the materials studied are a PTFE composite in contact with a high carbon steel plate. These materials are commonly used for industrial applications, in particular as the main contacting components within a scroll expander system. The expected contact temperature values are important to be quantified in order to...
-
Determinants of the primary stability of cementless acetabular cup implants: A 3D finite element study
PublicationPrimary stability of cementless implants is crucial for the surgical success and long–term stability. However, primary stability is difficult to quantify in vivo and the biomechanical phenomena occurring during the press–fit insertion of an acetabular cup (AC) implant are still poorly understood. The aim of this study is to investigate the influence of the cortical and trabecular bone Young's moduli Ec and Et, the interference...
-
Key-Marker Volatile Compounds in Aromatic Rice (Oryza sativa) Grains: An HS-SPME Extraction Method Combined with GC×GC-TOFMS
PublicationThe aroma of rice essentially contributes to the quality of rice grains. For some varieties, their aroma properties really drive consumer preferences. In this paper, using a dynamic headspace solid-phase microextraction (HS-SPME) system coupled to a two-dimensional gas chromatography (GC×GC) using a time-of-flight mass spectrometric detector (TOFMS) and multivariate analysis, the volatile compounds of aromatic and non-aromatic...
-
The possibility of estimating the height of the ionospheric inhomogeneities based on TEC variations maps obtained from dense GPS network
PublicationA state of the ionosphere can be effectively studied using electromagnetic signals received from global navigation satellite systems (GNSS). Utilization of the dual frequency observations allows estimating values of the total electron content (TEC). They can be used for a number of scientific studies such as detection and monitoring of traveling ionospheric disturbances or plasma bubbles. Moreover, maps of TEC variations allow...
-
Organic Acids and Polyphenols Determination in Polish Wines by Ultrasound-Assisted Solvent Extraction of Porous Membrane-Packed Liquid Samples
PublicationIn the near future, Poland is going to have more and more favorable conditions for viticulture. Organic acids and polyphenols are among the most commonly analyzed compounds due to their beneficial properties for human health and their importance in the winemaking process. In this work, a new technique involving ultrasound-assisted solvent extraction of porous membrane-packed liquid samples (UASE-PMLS) was for the first time described...
-
Improving the procedure of probabilistic load testing design of typical bridges based on structural response similarities
PublicationThis paper concerns load testing of typical bridge structures performed prior to operation. In-situ tests of a two-span post-tensioned bridge loaded with three vehicles of 38-ton mass each formed the input of this study. On the basis of the results of these measurements, an advanced FEM model of the structure was developed for which the sensitivity analysis was performed for chosen uncertainty sources. Three uncorrelated random...
-
Local variability in snow concentrations of chlorinated persistent organic pollutants as a source of large uncertainty in interpreting spatial patterns at all scales
PublicationSingle point sampling, a widespread practice in snow studies in remote areas, due to logistical constraints, can present an unquantified error to the final study results. The low concentrations of studied chemicals, such as chlorinated persistent organic pollutants, contribute to the uncertainty. We conducted a field experiment in the Arctic to estimate the error stemming from differences in the composition of snow at short distances...
-
Application of different building representation techniques in HEC-RAS 2-D for urban flood modeling using the Toce River experimental case
PublicationThis paper presents the impact of the choice of building representation techniques and hydrodynamic models on urban flood simulations using HEC-RAS 2-D for the Toce River physical model. To this end, eight numerical models based on previous laboratory experiments were prepared to simulate unsteady urban flooding on each side of building units. Two simplified building layouts (aligned and staggered) were examined, where models were...
-
COMPARISON OF PREDICTIVE METHODS FOR FLOW BOILING HEAT TRANSFER IN CONVENTIONAL CHANNELS AND MINICHANNELS – THE EFFECT OF REDUCED PRESSURE
PublicationIn the paper are presented the results of follow on studies from [1]–[3] using authors own model to predict heat transfer coefficient during flow boiling. The model has been tested against a large selection of experimental data collected from various researchers to investigate the sensitivity of the in-house developed model. The collected experimental data came from various studies from literature and were conducted for the full...
-
Evaluation of the suitability of electronic nose based on fast GC for distinguishing between the plum spirits of different geographical origins
PublicationPlum spirits are obtained exclusively via the alcoholic fermentation and distillation of meaty plums or must composed of plums, with or without stones. The European countries such as Poland, the Slovak Republic, the Czech Republic, Bulgaria and Romania are the leading producers of this alcoholic beverage. Information about the authentication of plum spirits produced in different countries can be found in the published literature....
-
Intelligent microbearing project with memory of stress-strain history
PublicationTaking into account the increasing need of intelligent micro-bearing with memory, this paper presents the optimization, simulation and practical application of operating parameters(load carrying capacity, friction forces, friction coefficient, wear), simulation for hydrodynamic HDD micro-bearing with curvilinear nano-grooved journal profile. One of the reason of such journal profile is that this journal profile contributes to the...
-
Degree of monopoly and market power vs. price flexibility in Polish economy: empirical analysis based on COICOP classification
PublicationResearch background: The issue of price flexibility is crucial in the economy both in the aspect of company theory and its macroeconomic consequences. In a number of publications, the sources of variable price flexibility are linked to the market power of enterprises as well as the market structure that has developed in a given branch. It is difficult to indicate empirical studies that would state clearly whether price flexibility...
-
Standard and modified falling mass impact tests on preplaced aggregatefibrous concrete and slurry infiltrated fibrous concrete
PublicationAlthough several studies have been conducted to evaluate the impact response of concrete using theAmerican Concrete Institute (ACI) 544-2R falling mass impact test, the variations in test results are themain drawback of this testing method. This study aims to reduce the variations in experimental impacttest results by introducing two simple test setup modifications; (1) using coarse or fine aggregate bed-ding as an alternative...
-
Improved surface coverage of an optical fibre with nanocrystalline diamond by the application of dip-coating seeding
PublicationGrowth processes of diamond thin films on the fused silica optical fibres (10 cm in length) were investigated at various temperatures. Fused silica pre-treatment by dip-coating in a dispersion consisting of detonation nanodiamond (DND) in dimethyl sulfoxide (DMSO) with polyvinyl alcohol (PVA) was applied. Nanocrystalline diamond (NCD) films were deposited on the fibres using the microwave plasma assisted chemical vapour deposition...
-
Discrepancies in determination of biogenic amines in beer samples by reversed phase and hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry
PublicationBiogenic amines (BAs) are nitrogenous organic bases occurring mainly in fermented food and beverages as a result of free amino acids bacterial decarboxylation. The reversed phase liquid chromatography (RPLC) and hydrophilic interaction liquid chromatography (HILIC) based methods were compared in terms of usefulness for determination of BAs in beer samples. Analysis of BAs with the use of RPLC method were carried out after their...
-
Time series analysis and impact assessment of the temperature changes on the vegetation and the water availability: A case study of Bakun-Murum Catchment Region in Malaysia
PublicationThe Bakun-Murum (BM) catchment region of the Rajang River Basin (RRB), Sarawak, Malaysia, has been under severe threat for the last few years due to urbanization, global warming, and climate change. The present study aimed to evaluate the time series analysis and impact assessment of the temperature changes on the vegetation/agricultural lands and the water availability within the BM region. For this purpose, the Landsat data for...
-
Towards hand grip force assessment by using EMG estimators
PublicationThe purpose of this study was to propose a method to assess individual regression (calibration) curves to establish a relationship between an isometric grip force and surface electromyography (EMG) estimator. In this study 18 healthy volunteers (12 male (23.0 ± 2.0 years) and 6 female (23.2 ± 0.7 years)) had been examined. Ten EMG estimators (mean absolute value, root mean square, entropy, energy, turns per second, mean of zero...