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1
Content available Prediction of the Properties of Modified Phenol-Formaldehyde Composites Using Mathematical Modeling of the Composition of the Polymer Mixture
Krasinskyi Volodymyr, Jachowicz Tomasz, Malinowski Rafał, Bajer Krzysztof, Dulebova Ludmila
Advances in Science and Technology. Research Journal
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2022
|
Vol. 16, no 4
138--146
EN
The paper presents the results of studies of adhesive strength under shearing, thermal stability, and the content of the gel fraction of adhesive materials and enamels based on modified phenol-formaldehyde resins. Epoxy resin and polyvinylpyrrolidone were used to modify the phenol-formaldehyde resin. The influence of the content of components in the phenol-formaldehyde composition and the curing conditions on the properties of the obtained adhesive materials and coatings is analyzed. The effect of polyvinylpyrrolidone on internal stresses in adhesive joints has been established. By mathematical planning, the isolines of the characteristics of composite materials based on modified phenol-formaldehyde resin depending on their component’s compositions are plotted, and the regression coefficients are found, enabling one to get materials with predicted properties. From a technical and economic point of view, the following content of additives in modified phenol-formaldehyde resin is most optimal: epoxy resin from 25 to 50 wt%, polyvinylpyrrolidone from 0.5 to 1.0 wt%, curing catalyst from 1 to 2.5 wt%.
2
Content available Developing the Regression Equations to Determine the Bankfull Discharge from the Basin Characteristics
Chau Tran Kim, Toan Nguyen The, Duc Do Anh, Linh Nguyen Ha
Archives of Hydro-Engineering and Environmental Mechanics
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2021
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Vol. 68, nr 2
103--117
EN
Bankfull discharge is an important criterion for flash flood warnings. In this study, the authors propose a new approach to determine the bankfull discharge for basins in Ha Giang province, Vietnam. The study combines the field survey to determine the bankfull discharge through the bankfull indicators and develop a multivariate regression equation between the bankfull discharge and the basin characteristics. The results of the study give a simple equation with 2 independent variables. They are the catchment area and the main river length. They show a strong relationship with the bankfull discharge with the R2 indexes in developing and validating process equal to 95.3% and 92.7%, respectively. With this approach, the workload is significantly reduced. However, the accuracy and flexibility of the total discharge calculation are enhanced. This will be the foundation to reduce uncertainty in flash flood warnings.
3
Content available Influence of COVID-19 coronavirus pandemic on international oil markets
Tvalchrelidze Alexander G., Silagadze Avtandil
Zeszyty Naukowe Akademii Morskiej w Szczecinie
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2020
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nr 63 (135)
97--103
EN
At the beginning of the COVID-19 coronavirus global pandemic, the oil market was crushed. In this period, the oil market was correlated with COVID-19 coronavirus world infection cases: more infected cases resulted in low oil prices, and the negative correlation between these two indices was very strong. Different factors determined the increase in both crude oil price and the number of oil futures contracts after April 20. Firstly, oil prices were driven by the coronavirus mortality rate, rather than by the absolute number of infection cases. The decisive driver for oil prices in the medium-term became pandemic development trends, instead of the actual epidemiological situation. This statement is proven by the statistical regression model of the interdependence between oil prices and COVID-19 coronavirus world mortality rate. Secondly, a gradual stable decrease in the coronavirus world mortality rate created an environment for the gradual restart of the world economy. Thirdly, the coronavirus mortality rate analysis provides investors with tangible guidelines to assess the medium-term sustainability of futures markets and, therefore, to elaborate investment strategies. Fourthly, after April 20, the oil market gradually achieved equilibrium, which is proven by a restored correlation between oil prices and the Euro-to-U.S. Dollar exchange rate. Three-month tendencies provide tangible guidelines for an optimistic forecast of the oil the market and maritime tanker business for the end of 2020 and all of 2021. So long as a new wave of COVID-19 does not dramatically increase mortality rates, the oil and maritime tanker trade market will regain the equilibrium it lost at the end of January
4
Content available Influence of machining parameters on surface texture of Inconel 718 after grinding with multi-granular wheels
Kopytowski Adrian, Świercz Rafał, Nowicki Rafał, Stambolov Grigor
Welding Technology Review
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2019
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R. 91, nr 3
13--20
EN
Requirements currently imposed on machine elements are constantly growing. It requires to develop new, advanced machining processes. One of the commonly used finishing process is grinding. The article presents the results of the exploratory research in the process of surface grinding with abrasive multigrain wheels of samples made of Inconel 718. The influence of input parameters was investigated: cutting speed Vc, transverse feed speed Fp, longitudinal feed speed Fw, on roughness parameters (Sa) and the bearing capacity curve. Based on the conducted research, statistical models of the grinding process were elaborated, which allow to select the most favorable processing parameters depending on the required quality of the surface texture.
PL
Wymagania obecnie nakładane na elementy maszyn stale rosną. Powoduje to konieczność opracowania nowych, zaawansowanych procesów obróbki. Jednym z powszechnie stosowanych procesów wykańczających jest szlifowanie. W artykule przedstawiono wyniki badań rozpoznawczych procesu szlifowania powierzchni próbek wykonanych z Inconelu 718, ściernicami wielogranulacyjnymi. Zbadano wpływ parametrów wejściowych: prędkości skrawania Ve, prędkości posuwu poprzecznego Fp, prędkości posuwu wzdłużnego Fw, na parametr chropowatości (Sa) i krzywą nośności. Na podstawie przeprowadzonych badań opracowano modele statystyczne procesu szlifowania, które pozwalają wybrać najkorzystniejsze parametry obróbki w zależności od wymaganej jakości wykończenia powierzchni.
5
Content available Determining of correlation relationship between roll, pitch, and yaw for UAVs
Hlotov Volodymyr, Hunina Alla, Yurkiv Mariana, Siejka Zbigniew
Reports on Geodesy and Geoinformatics
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2019
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Vol. 107
13--18
EN
Currently, UAVs are intensively being introduced into topographic-photogrammetric production for topographic digital aerial photography and laser scanning. These technologies have a number of advantages: they don’t require specially prepared platforms and launchers, they are relatively inexpensive unlike large aircrafts, and they are safe. However, there are still many unsolved problems for ultralight UAVs, especially when the aerial photography is made. As you know, the requirements for the implementation of the aerial survey process are quite stringent, first of all, for horizontal flight: the angles of inclination must be within 3–5 degrees, since exceeding these tolerances significantly affects the accuracy for determining the spatial coordinates of objects. Therefore, there was an idea to conduct researches of dependences between the pitch α, roll ω and yaw κ. For this purpose, 100 images obtained from aircraft-type UAV ‘Arrow’ developed and created by specialists from Lviv Polytechnic National University and ‘Abris’ were used. As a result of the study, the multiple correlation coefficient and the parameters of the linear regression equation for the angular elements of the exterior orientation of digital images were calculated. In addition, statistical quality evaluations for the obtained regression model were carried out. Analysis of the received data allows to assert that angular elements of exterior orientation are correlated with each other. Therefore, in the further imaging materials, processing it becomes possible to make compensation of this fact and to improve calculation accuracy of spatial coordinates of points.
6
Content available Development of a mathematical model of the generalized diagnostic indicator on the basis of full factorial experiment
Sychenko V. G., Mironov D. V.
Archives of Transport
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2017
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Vol. 43, iss. 3
125--133
EN
Purpose. The aim of this work is to develop a mathematical model of the generalized diagnostic indicator of the technical state of traction substations electrical equipment. Methodology. The main tenets of the experiment planning theory, methods of structural-functional and multi-factor analysis, methods of mathematical and numerical modeling have been used to solve the set tasks. Results. To obtain the mathematical model of the generalized diagnostic indicator, a full factorial experiment for DC circuit breaker have been conducted. The plan of the experiment and factors affecting the change of the unit technical condition have been selected. The regression equation in variables coded values and the polynomial mathematical model of the generalized diagnostic indicator of the circuit breaker technical condition have been obtained. On the basis of regression equation analysis the character of influence of circuit breaker diagnostic indicators values on generalized diagnostic indicator changes has been defined. As a result of repeated performances of the full factorial experiment the mathematical models for other types of traction substations power equipment have been obtained. Originality. An improved theoretical approach to the construction of generalized diagnostic indicators mathematical models for main types of traction substations electric equipment with using the methods of experiments planning theory has been suggested. Practical value. The obtained polynomial mathematical models of the generalized diagnostic indicator D can be used for constructing the automated system of monitoring and forecasting of the traction substations equipment technical condition, which allows improving the performance of processing the diagnostic information and ensuring the accuracy of the diagnosis. Analysing and forecasting the electrical equipment technical condition with the using of mathematical models of generalized diagnostic indicator changes process allows constructing the optimal strategy of maintenance and repair based on the actual technical condition of the electrical equipment. This will reduce material and financial costs of maintenance and repair work as well as the equipment downtime caused by planned inspections and repair improving reliability and uptime of electrical equipment.
7
Content available Kryteria wyboru adekwatnej funkcji trwałości ostrza skrawającego w programach krokowej regresji wielokrotnej. Cz. II – przykład aplikacji
Filipowski R.
Obróbka Metalu
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2015
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nr 4
40--42
PL
W pracy wykorzystano metodę krokowej regresji wielokrotnej, która pozwala wybrać funkcje o możliwie małej liczbie zmiennych niezależnych oraz ich interakcji. Dobór funkcji regresji przedstawiono na przykładzie badań trwałości ostrza z węglika spiekanego podczas skrawania stali C45. Trwałość ostrza ustalono w/g kryterium zużycia VBB na powierzchni przyłożenia ostrza. Badania były wykonywane w/g planu kompozycyjnego pięciopoziomowego dla trzech zmiennych niezależnych: prędkości skrawania vc posuwu na obrót f oraz głębokości skrawania ap. Uzyskane funkcje regresji mają trzy formy: pierwsza - liniową z interakcjami w skali równomiernej, druga, także liniowa lecz z interakcjami w skali logarytmicznej oraz trzecia w formie iloczynowej. Przyjęcie jednej z form funkcji regresji ustala prowadzący badania na podstawie analizy statycznej i analizy reszt.
EN
Method of stepwise multiple regression enable to select a function with the possible smallest number of independent variables and its interactions. Liminal criteria of variables selection were described using stepwise multiple regression program REGSTEP, worked out on the base of work [3], and in well-known program STATISTICA.
8
Content available Kryteria wyboru adekwatnej funkcji trwałości ostrza skrawającego w programach krokowej regresji wielokrotnej. Cz. I - Metodyka
Filipowski R.
Obróbka Metalu
|
2015
|
nr 3
46--49
PL
Metoda krokowej regresji wielokrotnej pozwala wybrać funkcje o możliwie małej liczbie zmiennych niezależnych oraz ich interakcji. Opisano kryteria progowe selekcji zmiennych w programie krokowej regresji wielokrotnej REGSTEP, opracowanym na podstawie pracy [4] oraz w znanym programie STATISTICA.
EN
Method of stepwise multiple regression enable to select a function with the possible smallest number of independent variables and its interactions. Liminal criteria of variables selection were described using stepwise multiple regression program REGSTEP, worked out on the base of work [3], and in well-known program STATISTICA.
9
Content available remote Stress Relaxation in Copper Bolted Busbar Assemblies with New Design Concept of the Bolt Holes
Dineff P., Dikov V., Tzeneva R.
Przegląd Elektrotechniczny
|
2013
|
R. 89, nr 2a
242--246
EN
This article reports experimental investigation results of the stress relaxation in copper bolted busbar assemblies with new design concept of the bolt holes (S-design and G-design). The results of the new case are compared with the results of the classical case of the same assemblies and it is observed that for the new S- and G- designs the decrease in the fastening force is quite low which stands for a higher level of reliable assembly operation.
PL
W artykule opisano badania eksperymentalne, dotyczące naprężeń w zespole miedzianych szyn zasilających o połączeniach śrubowych. Zastosowano nową propozycję otworów śrubowych, które, po porównaniu z klasycznymi metodami, wykazały mniejszy spadek siły docisku, co przekłada się na zwiększoną niezawodność połączenia.
10
Content available Przykłady zastosowań metod planowania i oceny eksperymentu w tomografii impedancyjnej i mikroskopii elektronowej
Oskwarek Ł.
Pomiary Automatyka Kontrola
|
2011
|
R. 57, nr 11
1289-1292
PL
Przedmiotem artykułu są wybrane zagadnienia z teorii eksperymentu, takie jak: testowanie hipotez statystycznych, ocena istotności wpływu czynników oraz ocena postaci równania regresji. Wiedza z tego zakresu została wykorzystana do oceny wyników pomiarów wykonanych na potrzeby impedancyjnej tomografii komputerowej (ocena krzywych poprawek, ocena wpływu czynników związanych z układem pomiarowym) oraz skaningowej mikroskopii elektronowej (ocena równania opisującego zniekształcenia obrazów pod wpływem zewnętrznego pola zakłócającego).
EN
In the paper selected problems of the theory of experiment like: statistical hypotheses testing, assessment of the significance of impact factors and evaluation of a regression equation [1, 2, 3, 4, 5, 6] are presented. Knowledge of this area may be useful for engineers when assessing the method of measurement and operation of a developed system. From the analysis performed for impedance tomography [7, 8, 9], using planning and evaluation of experiment methods, one can draw the following conclusions: although it is necessary to introduce corrections to the raw measurements, their values can be approximated by a linear regression curve, it is possible to follow the same correction curves (Fig.1) and the associated uncertainty for measurement results obtained by excitation of different pairs of electrodes, most of parameters relating to the measurement system, in the examined range of variation, had no significant effect on the obtained results - thanks to that, conclusions presented in the paper are more universal. In turn, the calculations performed for microscopic research [10, 11] showed that the derived forms of the regression equation (Fig. 2) describe correctly the empirical data, and the reproducibility of performed experiments was satisfactory. This improves reliability of the results concerning evaluation of the impact of the external magnetic field on the distortion level of observed images.
11
Content available Statistical analysis of gaz-3110 vehicles noise
Pobedin A., Kosov O., Dolotov A., Domolazov F.
Journal of KONES
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2009
|
Vol. 16, No. 1
407-410
EN
This work presents the results of the statistical analysis of noise in several points of GAZ-3110 vehicles. There are also the dependences between the loudness of noise and speed of an engine or useful life of a car. It is difficult to confuse the noise of jet engine with reciprocating internal-combustion engine. Random factors also influence much the power level. Mechanism adjustment has its limits and so it can have different influence on its vibration and noise. Finally during the process of operation sliding surfaces do wear, screwed connections do loosen, other things happen and these lead to the changes in spectrum and level of noise. In this work we tried to evaluate the dispersion of GAZ-3110 vehicles noise levels according to the results of a coustic measurements in the immediate field of rondom acoustically active constructive assemblies. The range of noise loudness for the specific car model is defined at the level 20-25 dBA. The GAZ-3110 vehicles are characterized by the significant dispersion of noise level. The differences of noise level of individual cars are exceeding 20-25 dBA. vehicles noise considerably increases with the augmentation of useful life and rpm speed. The noisiest element of GAZ-3110 vehicles is internal combustion engine, then main gear even when first gear is operated.
12
Content available Wpływ mikronizacji na aktywność neurotoksyn lędźwianu siewnego oznaczanych z zastosowaniem metody wskaźnika purpury bromokrezolowej (BCPI)
Szmigielski M., Matyka S., Masłowski A.
Inżynieria Rolnicza
|
2005
|
R. 9, nr 11
455--462
PL
Zbadano wpływ promieniowania mikrofalowego na aktywność neurotoksyny lędźwianu siewnego oznaczanej jako kwas β-N-oxalyl-L-α-β-diaminopropionowy - BOAA). Zweryfikowano hipotezę wskazującą na możliwość zastosowania wskaźnika purpury bromokrezolowej (BCPI) jako sposobu oceny aktywności tej neurotoksyny. Próby lędźwianu siewnego odmiany Krab (o masie 50g), które zastosowano w badaniach, przygotowano każdorazowo poprzez naświetlenie nie rozdrobnionych nasion w komorze roboczej kuchenki mikrofalowej. Zastosowano dziesięć wariantów intensywności ogrzewania, w których każdemu z trzech poziomów mocy promieniowania (350, 500 lub 650 W) odpowiadały trzy czasy ogrzewania (60, 120 lub 180 s), zaś jedną z prób pozostawiono bez obróbki termicznej. Duża współzależność wyników uzyskanych metodami BCPI i BOAA (współczynnik korelacji r = 0,89), oraz wysokie współczynniki dopasowania (R2) równań regresji BOAA = f(BCPI) do danych doświadczalnych wskazują na znaczącą wiarygodność operacji wzajemnego przeliczania wyników uzyskanych tymi metodami dla mikronizowanych nasion lędźwianu siewnego.
EN
Effect of microwave radiation on the activity of ever-lasting pea (Lathyrus latifolius) neurotoxin, designated as β-N-oxalyl-Lα-β diaminopropionic acid (BOAA), was studied. A hypothesis suggestion the possibility of using bromocresol purple index (BCPI) as a method to evaluate the activity of this toxin was verified. Samples of the everlasting pea, Krab cultivar, 50 g in weight, used in tests were prepared each time by irradiation of whole seeds inside a chamber of microwave oven. Ten variants of heating intensity were applied: at each of three radiation power levels (350, 500, 650 W), three times of heating were used (60, 120, 180 s), whereas one sample left without any heat treatment. Strong interrelation of the results obtained by BCPI and BOAA methods (correlation coefficient r=0.89) as well as high matching coefficients (R2) and regression equations BOAA=f(BCPI) to experimental data, showed a significant reliability of methods for micronized everlasting pea seeds.
13
Content available remote The Experimental Measurement of the Tire Impurities Circulation by the Dynamic Loading and Application of the Experimental Evaluation by the Method of the Active Factor Experiment
Vavro J., Kopecký M., Koštial P., Hajská H., Fandáková M.
Machine Dynamics Problems
|
2004
|
Vol. 28, No. 4
171-176
EN
The article is dealing with the measurement of the tire impurities circulation by the dynamic loading along with the disc. There are made measurements for the various tire velocities on the roadway by the constant inflation pressure in tire and by the tire constant external loading and time service longitudes. In the article is suggested the process of the measurement evaluation by the method of the active factor experiment.
14
Content available remote Statistical calculus of wear for the sliding rings in face seal
Popa N., Enescu M.
International Journal of Applied Mechanics and Engineering
|
2004
|
Vol. 9, no spec.
173-175
EN
The main advantage of the statistic calculus of wear is that it uses the real situation of the system with experimental data resulted from the action of the involved factors. Thus it was experimentally determined the wear speed of the primary seal in a face seal system. The equation of statistical regression resulted form the mathematical moulding of the wear process. The paper presents the rate of some parameters having influences on the wear of face seal.
15
The properties of the process of reduction of nitrogen oxides on a carbon sorbent.
Jastrząb K., Szarawara J.
Archiwum Ochrony Środowiska
|
1998
|
Vol. 24, no. 4
59-75
EN
The influence of temperature and the composition of gases on the reduction of nitrogen oxide with ammonia on the Polish sorbent, assigned for the purification of combustion gases has been investigated. These investigations were carried out in a flow system with stationary carbon sorbent layer. The dependence of the reduction degree of nitrogen oxide on the space time of the purified gases with the sorbent layer, as well as on the temperature and concentration of NO, NH3, H2O and O2 has been determined. These relation have been expressed by mean of regression equations. The optimal conditions of the process have been determined, viz temperature and the excess of ammonia. Apart from their cognitive significance, the obtained results may serve the purpose of describing quantitatively the reduction process of nitrogen oxide.
PL
Przebadano wpływ temperatury i składu gazów na przebieg redukcji tlenku azotu amoniakiem na polskim sorbencie węglowym przeznaczonym do oczyszczania spalin. Badania prowadzono w układzie przepływowym z nieruchomym złożem sorbentu węglowego. Wyznaczono zależności stopnia redukcji tlenku azotu od czasu zetknięcia oczyszczonych gazów ze złożem oraz temperatury i stężenia NO, NH3, H2O i O2. Zależności te opisano odpowiednimi równaniami regresji. Ustalono optymalne warunki procesu: temperaturę i nadmiar amoniaku. Otrzymane wyniki oprócz znaczenia poznawczego mogą posłużyć do ilościowego opisu procesu redukcji tlenku azotu.
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