Wyniki wyszukiwania - BazTech

1

Sisneros Kayla, Maurya Pratibha, Johnson Evan, Ford Benton, Palmer Ty

Acta of Bioengineering and Biomechanics

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2023

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Vol. 25, no. 1

19--26

EN

This study aimed to examine the effects of age on vertical jump height and handgrip strength measurements in women. A secondary aim was to investigate the correlations between vertical jump height and handgrip strength. Methods: Twenty young (21.5 ± 2.8 years) and twenty older (67.0 ± 5.5 years) healthy women participated in this study. Handgrip contractions were used to assess strength measurements of peak force and rate of force development at different time intervals. Vertical jumps were performed on a jump mat. The jump mat measured vertical jump height based on flight time. Results: The older women had lower vertical jump height (P < 0.001) and handgrip peak force (P = 0.028) and rate of force development values (P = 0.003–0.016) than the younger women. A larger difference was observed between the groups for vertical jump height (41%) than handgrip peak force and rate of force development (12–17%). Of all the strength measurements, handgrip rate of force development at 200 ms in the young (r = 0.502, P = 0.024) and older (r = 0.446, P = 0.049) women exhibited the strongest correlation with vertical jump height. Conclusions: This investigation showed significantly lower vertical jump height and handgrip peak force and rate of force development values in older compared to younger women. Interestingly, the difference between age groups was larger for jump height than handgrip peak force and rate of force development. This suggests that vertical jump performance may be more severely affected by age than handgrip strength characteristics.

2

Experimental and numerical investigation of scour downstream contracted spillways

Nasralla Tarek H.

Journal of Water and Land Development

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2022

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no. 52

53--59

EN

A study of scour downstream of free hydraulic jump in stilling basin of stepped spillways was carried out. This paper employed an experimental study to investigate the stepped spillway with the movable bed material of D50= 3.1 mm. The effect of the contraction ratio of the stepped spillway was highlighted. Different downstream divergent angle was studied to minimise the scour depth, the results showed that the relative scour depth was reduced by 23% for divergent angle is equal to 170°, different shapes of buffer in stilling basin were also studied to reduce the scour depth where the considered buffer decrease the relative scour depth up to 84%. This study was simulated by Flow 3D program to analyse the scour hole formed using velocity vectors at the bed. The simulated results well agreed with the measured data.

3

Iteracje odwzorowań, orbity, twierdzenie Banacha o punkcie stałym

Ludew Jan Jakub, Różański Michał, Smoleń-Duda Barbara, Wituła Roman, Czernik Szymon

MINUT Matematyka i Informatyka na Uczelniach Technicznych

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2021

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Nr 3

166-195

PL

Praca stanowi zbiór zadań i problemów poświęconych wprowadzeniu w teorią punktów stałych, która realizowana jest jedynie w zarysie na drugim semestrze studiów na kierunku matematyka. Stanowi niezależny byt, ale w gruncie rzeczy jest uzupełnieniem finalizowanego opracowania teoretycznego, które również zamierzamy opublikować w tym czasopiśmie.

4

L ∞-error estimates of a finite element method for Hamilton-Jacobi-Bellman equations with nonlinear source terms with mixed boundary condition

Miloudi Madjda, Saadi Samira, Haiour Mohamed

Demonstratio Mathematica

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2021

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Vol. 54, nr 1

452--461

EN

In this paper, we introduce a new method to analyze the convergence of the standard finite element method for Hamilton-Jacobi-Bellman equation with noncoercive operators with nonlinear source terms with the mixed boundary conditions. The method consists of combining Bensoussan-Lions algorithm with the characterization of the solution, in both the continuous and discrete contexts, as fixed point of contraction. Optimal error estimates are then derived, first between the continuous algorithm and its finite element counterpart and then between the continuous solution and the approximate solution.

5

Rodzaje skurczu betonu, ich znaczenie i metody zapobiegania

Kurdowski Wiesław

Cement Wapno Beton

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2021

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R. 26, nr 2

109--117

PL

Jedną z niekorzystnych właściwości betonu stanowi skurcz, który jest spowodowany zmianami objętościowymi zaczynu cementowego. Wyróżniamy następujące rodzaje skurczu: skurcz chemiczny nazywany także kontrakcją lub skurczem Le Chatelier, skurcz plastyczny, skurcz autogeniczny, czasem zwany także skurczem auto-suszenia i skurcz suszenia. Opracowano szereg metod w celu usunięcia tego skurczu. Krystalizacja ettringitu jest jedną z metod i jest oparta na dodatku kompleksu Kleina do cementu. Są także stosowane domieszki organiczne, które opierają się na zmniejszeniu napięcia powierzchniowego wody w kapilarach. W pracy zbadano wpływ domieszki BASF Master Life SRA 815 samej i z dodatkiem CaO. W przeprowadzonych doświadczeniach wykazano, że CaO powoduje bardzo małe zmniejszenie skurczu, natomiast wymieniona domieszka daje duże zmniejszenie skurczu. Równoczesny dodatek CaO do Master Life SRA 815 powoduje zwiększenie wpływu tej ostatniej. Także dodatek samego kompleksu Kleina nie spowodował zmniejszenia skurczu, natomiast jego dodatek do Master Life SRA 815 zwiększył zmniejszenie skurczu.

EN

One of the unfavourable properties of concrete is shrinkage which is linked with the volume changes of cement paste. We distinguish the following kinds of shrinkage: – “chemical” shrinkage called also the contraction or Le Chatelier shrinkage, – plastic shrinkage, – autogenic shrinkage or spontaneous, sometimes called auto drying, – drying shrinkage. There are several methods to eliminate concrete shrinkage. The ettringite crystallization is one of the inorganic compounds methods and is based on Klein’s complex addition to cement. This complex is causing the rapid ettringite formation and the shrinkage is diminished. There are also organic admixtures which action is the reduction of the water surface tension. There are surface-active additions that are reducing this tension, in capillaries. The organic admixtures which are diminishing the shrinkage are based on neopentyl glycol or similar chemical compounds. In the study, the shrinkage-reducing admixture BASF Master Life SRA 815 alone and with CaO addition were examined. It was shown that CaO addition is giving very low diminishing of cement shrinkage, contrary to the fluid admixture Master Life SRA 815 which has a high diminishing influence on cement shrinkage. However, the simultaneous addition of CaO is increasing the diminishing influence of this fluid admixture. The addition of Klein’s complex does not influence of shrinkage but its simultaneous addition with Master Life SRA 815 gives higher shrinkage diminishing.

6

Granger causal analysis of electrohysterographic and tocographic recordings for classification of term vs. preterm births

Saleem Saqib, Saeed Ahmed, Usman Shabnam, Ferzund Javed, Arshad Jahangir, Mirza Jawad, Manzoor Tareq

Biocybernetics and Biomedical Engineering

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2020

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Vol. 40, no. 1

454--467

EN

According to World Health Organization, 5-18% births around the world are premature, and this rate is on its rise. Recent trend has been to develop computational tools which could support obstetricians in their daily practice. This work is aimed at extracting novel diagnostic features for term vs. preterm births classification based on the dynamics of contraction and non-contractions (dummy) intervals. To achieve this, 26 uterine records of 18 pregnant women, resulting in 13 term and 13 preterm deliveries, were analyzed in this study. Each record was of 30-min duration, and comprised three electrohysterographic (EHG) and one externally recorded tocographic (Toco) signal. Granger causal analysis of contraction and dummy intervals of recorded signals was performed to extract potential features. These include coupling strength and directionality indices, and were subsequently utilized by a quadratic discriminator to classify between term and preterm births. The extracted features achieved high discriminatory power of 94%, 95%, 91%, and 97% for sensitivity, specificity, classification accuracy, and area under the ROC curve, respectively. These findings show that Granger causal analysis might be adopted as a computational tool to quantify EHG-Toco dynamics for the risk-assessment of the preterm delivery.

7

Flexinol properties study

Harazin Jacek, Kost Gabriel

Selected Engineering Problems

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2019

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nr 8

27--32

EN

This article contains study concerning flexinol wire’s contraction time and length. During the research, to stimulate the wire, a modulated PWM signal was used. Changes in PWM duty cycles were causing greater heat accumulation which led to faster structural transformation of the wire and in result different contraction times and lengths. The research stand and control system that were used to stimulate the flexinol wire (regulated PWM wave stimulation) and measure its contraction times, and lengths, were also described in this article.

8

Testing contraction and thermal expansion coefficient of construction and moulding polymer composites

Pyrzowski Ł.

Polish Maritime Research

|

2018

|

S 1

151--158

EN

The paper presents results of systematic tests of contraction and thermal expansion coefficients of materials based on polymer composites. The information on the above material properties is essential both at the design stage and during the use of finished products. Components for the samples were selected in such a way as to represent typical materials used for production of construction and moulding elements. The performed tests made it possible to monitor the analysed parameters at different stages of the technological process.

9

Some extensions of banach contraction principle in G-metric spaces

Gaba Y. U.

Fasciculi Mathematici

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2018

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Nr 61

55--70

EN

We present different extensions of the Banach contraction principle in the G-metric space setting. More precisely, we consider mappings for which the contractive condition is satisfied by a power of the mapping and for which the power depends on the specified point in the space. We first state the result in the continuous case and later, show that the continuity is indeed not necessary. Imitating some techniques obtained in the metric case, we prove that under certain conditions, it is enough for the contractive condition to be verified on a proper subset of the space under consideration. These results generalize well known comparable results.

10

Multi-phase flow mixture through a sudden change in channel cross-section

Wiśniowska J., Witczak S., Pietrzak M.

Czasopismo Techniczne. Mechanika

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2016

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Y. 113, iss. 2-M

225--236

EN

The paper presents the results of a study involving the impact of sudden change of crosssectional area on the flow patterns and local pressure drops for flow of multi-phase mixture. The experiment was conducted in the conditions of a horizontal and vertical flow through a measuring channel. Pressure drops calculated on the basis Kawahara and Lottes methods are compared with experimental data. A system of two interconnected pipes with internal diameters of 40 and 22 mm as well as 46 and 16 mm and a total length of 7 m formed the measurement channel. The experiments involved air, water and oil.

PL

W pracy przedstawiono wyniki badań dotyczących wpływu gwałtownej zmiany pola przekroju poprzecznego kanału na struktury przepływu oraz miejscowe straty ciśnienia w przepływie mieszaniny wielofazowej. Porównano spadki ciśnienia obliczone na podstawie metod Kawahary i Lottesa z wartościami eksperymentalnymi. Badania prowadzono w warunkach poziomego i pionowego przepływu przez kanał pomiarowy z przeszkodą lokalną. Kanał pomiarowy stanowił układ dwóch rur o średnicach wewnętrznych 40 i 22 mm oraz 46 i 16 mm i całkowitej długości 7 m. Fazę gazową stanowiło powietrze, a fazę ciekłą olej maszynowy i woda.

11

Wpływ stosowania drobnego kruszywa z recyklingu na wybrane właściwości kompozytów cementowych

Pawluczuk E., Kozak K.

Budownictwo i Inżynieria Środowiska

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2016

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Vol. 7, no. 1

39--45

PL

Praca dotyczy ustalenia wpływu stosowania drobnego kruszywa z recyklingu na wybrane właściwości kompozytów cementowych. Frakcję z recyklingu uzyskano w wyniku rozdrobnienia wcześniej przygotowanych do tego celu próbek laboratoryjnych z normowej zaprawy cementowej. Do zrealizowania badań zaplanowano pełny eksperyment obejmujący w sumie 11 serii, w którym zmiennymi były: zawartość drobnego kruszywa z recyklingu (0-60%) oraz temperatura jego prażenia (0-850°C). Na podstawie uzyskanych wyników badań stwierdzono, że drobne kruszywo z recyklingu generalnie negatywnie wpływa na badane właściwości kompozytów cementowych. Efekt ten może być jednak ograniczony poprzez zastosowanie obróbki termiczno-mechanicznej drobnej frakcji recyklingowej.

EN

The paper concerns the determination of the influence of using the fine recycled aggregates on selected properties of cement composites. Fine recycled aggregate was achieved as a result of crushing laboratory samples made of standardised cement mortar. To perform the test complete experiment consisting of 11 series was planned. Two different variables were: X1 – content of fine recycled aggregate (0-60%) and X2 – the temperature of mortar rubble roast (0-850°C). Based on the obtained results it was found that the fine recycled aggregate generally deteriorates the tested properties of cement composites. On the other hand this effect may be significantly limited by the use of thermal-mechanical treatment of recycled rubble.

12

Matroids And Greedy Algorithms. A Deeper Justification of Using Greedy Approach To Find A Maximal set of a Matroid

Haider S. A.

Annales Universitatis Mariae Curie-Skłodowska. Sectio AI, Informatica

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2016

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Vol. 16, no. 2

48--50

EN

Greedy algorithms are used in solving a diverse set of problems in small computation time. However, for solving problems using greedy approach, it must be proved that the greedy strategy applies. The greedy approach relies on selection of optimal choice at a local level reducing the problem to a single sub problem, which actually leads to a globally optimal solution. Finding a maximal set from the independent set of a matroid M(S, I) also uses greedy approach and justification is also provided in standard literature (e.g. Introduction to Algorithms by Cormen et .al.). However, the justification does not clearly explain the equivalence of using greedy algorithm and contraction of M by the selected element. This paper thus attempts to give a lucid explanation of the fact that the greedy algorithm is equivalent to reducing the Matroid into its contraction by selected element. This approach also provides motivation for research on the selection of the test used in algorithm which might lead to smaller computation time of the algorithm.

13

Rough Set Characterization for 2-circuit Matroid

Wang S., Zhu Q., Zhu W., Min F.

Fundamenta Informaticae

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2014

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Vol. 129, nr 4

377--393

EN

Rough sets are efficient to extract rules from information systems. Matroids generalize the linear independency in vector spaces and the cycle in graphs. Specifically, matroids provide well-established platforms for greedy algorithms, while most existing algorithms for many rough set problems including attribute reduction are greedy ones. Therefore, the combination between rough sets and matroids may bring new efficient solutions to those important and difficult problems. In this paper, 2-circuit matroids, abstracted from matroidal characteristics of rough sets, are studied and axiomatized. A matroid is induced by an equivalence relation, and its characteristics including the independent set and duality are represented with rough sets. Based on these rough set representations, this special type of matroid is defined as 2-circuit matroids. Conversely, an equivalence relation is induced by a matroid, and its relationship with the above induction is further investigated. Finally, a number of axioms of the 2-circuit matroid are obtained through rough sets. These interesting and diverse axioms demonstrate the potential for the connection between rough sets and matroids.

14

Volume contraction in the process of combustion of various fuels in combustion engines

Worsztynowicz B.

Combustion Engines

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2013

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R. 52, nr 3

72--78

EN

The paper discusses the issues related to the change of volume of the reagents during the process of combustion. The formulas that were necessary to make the calculations were derived for liquid and gaseous fuels. Based on the formulas, theoretical calculations of the change of the kilo-mole number for various fuels depending on the mixture composition were performed. The results of the calculations were presented in the tables. Further, the influence of volume contraction on the parameters of the combustion process was analyzed. In the conclusions, a comparison of the influence of the previously described phenomena on the individual fuels was performed in relation to their chemical composition and the composition of the mixture.

PL

W artykule poruszono zagadnienia związane ze zjawiskiem zmiany objętości reagentów podczas procesu spalania. Wyprowadzono konieczne do obliczeń wzory dla paliw ciekłych i gazowych, na podstawie których przeprowadzono teoretyczne obliczenia zmiany liczby kilomoli dla różnych paliw w zależności o składu mieszanki palnej. Wyniki obliczeń zostały przedstawione w tabelach. Następnie przeanalizowano wpływ zjawiska kontrakcji na parametry procesu spalania. We wnioskach dokonano porównania wpływu opisanych wcześniej zjawisk na poszczególne paliwa w zależności od ich składu chemicznego oraz składu mieszanki palnej.

15

Izotermy sorpcji gazu przy różnych obciążeniach okólnych węgla

Dutka B., Kudasik M.

Prace Instytutu Mechaniki Górotworu PAN

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2012

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Vol. 14, no. 1-4

25--31

PL

Praca podejmuje aspekty bilansowania gazu zasorbowanego przez próbkę węglową przy różnych obciążeniach okólnych węgla. Próbkę nasycano CH4 do kolejnych ciśnień równowagi sorpcyjnej. Dla każdego punktu równowagi sorpcyjnej, przy utrzymywaniu stałego ciśnienia CH4, węgiel poddawano cyklom sorpcji-desorpcji poprzez bezpośrednią zmianę obciążenia okólnego wywieranego na próbkę. Badano wpływ zmian zewnętrznego obciążenia okólnego próbki na proces sorpcji CH4. Szczególną uwagę poświęcono zagadnieniu odwracalności, inicjowanych poprzez zmianę obciążenia, procesów sorpcyjnych. Autorską aparaturę wysokociśnieniową do pomiarów sorpcji gazu w warunkach obciążenia okólnego próbki, na której przeprowadzone zostały badania, rozbudowano o część pozwalającą na śledzenie procesu desorpcji. Dokonana modyfikacja pozwala badać w sposób bezpośredni relację pomiędzy pojemnością sorpcyjną węgla i obciążeniem, jak również kompleksowo dokonywać rejestracji procesów sorpcji/desorpcji wraz z pomiarami efektów odkształceniowych próbki (pęcznienie/kontrakcja).

EN

The study investigates the equilibrium condition of gas sorbed by a coal sample under various coal loading due to ambient conditions. The sample was saturated with CH4 to reach the subsequent sorption equilibrium pressures. The pressure of CH being held constant, for each sorption equilibrium point the sample was subjected to sorption-desorption cycles through direct changes of the ambient pressure acting upon coal. Testing was done to find out how changes of the external loading acting on the coal sample due to ambient conditions should affect the process of CH4 sorption. Special attention is given to reversibility of the sorption processes triggered by load variations. The high-pressure apparatus designed by the authors was extended to incorporate the system for monitoring the sorption processes. This modification allows the relationship between the sorption capacity and the coal sample loading to be investigated by direct methods and the sorption/desorption processes to be registered alongside the results of strain measurements (coal swelling/contraction).

16

Two-phase gas-liquid flow in conditions of expansion and contraction of channel

Witczak S., Wiśniowska J.

Journal of Energy Science

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2012

|

Vol. 1, nr 2

135--143

EN

The paper presents the results of studies concerning the effects of sudden change of cross-sectional area on the flow patterns and local pressure losses in the horizontal flow of two-phase mixture. The scope of research include the observation of flow patterns of flowing mixture and their disturbances caused sudden change in cross-section of the pipeline. In addition, flow resistance affecting pressure change before and after the local obstacle were measured. The experiment was conducted in a horizontal flow through the measuring channel with a local obstacle in the form of a sudden change in channel cross-sectional area. Measurement channel was a system of two interconnected tubes with internal diameters of 40 and 22 mm and a total length of 7 m. The air, water and oil were used in the experiments. Analysis of the experimental data leads to the conclusion that the mathematical model for calculating the two-phase flow pattern disturbance areas and their impact on the value of the pressure drop in the pipe with a sudden expansion and contraction should take into account both the parameters of the liquid phase and gas phase.

17

L-approach merotopies and their categorical perspective

Khare M., Tiwari S.

Demonstratio Mathematica

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2012

|

Vol. 45, nr 3

699-716

EN

In the present paper, we have made a category theoretic and lattice theoretic study of some nearness-like structures in the L-approach theory. Using L-grills, the notion of L-approach grill structure is introduced as a characterization of L-approach grill merotopy on X; their categorical perspectives and implications are also investigated. A number of illustrative examples are included.

18

Increase of liquid metal utilization during production of bearing circle castings for cement furnaces

Zadera A., Senberger J., Carbol Z., Pluhaček J.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 2

111-116

EN

In manufacture of super heavy castings for cement furnaces a saving of liquid metal has been achieved by lowering the riser weight. By solidification modelling with the aid of the Niyama criterion a zone in the riser was designated where the occurrence of foundry defects (shrinkage porosity) can be expected. A plate of the material of dimensions ca 700*800*250 mm was taken from the riser. After thermal treatment the samples for making the bars for the static tensile test were taken from it. Based on done tests it has been found out that mechanical characteristics obtained from the static tensile test correlate, besides contraction, in the chosen level of statistical importance of p = 0.01 with carbon content. Neither in the zone of probable occurrence of defects designated by the Niyama criterion during solidification modelling the drop of strength characteristics was observed. Carbon content in a decisive extent influenced the strength characteristics. In case of ductility and contraction the convenient correlations with carbon content were observed from the riser height of 200 mm only. In the height of 400 mm there was already considerable variation of values and some values were lower ones than is demanded by standards.

19

Miejscowe straty ciśnienia przy przewężeniu kanału poziomego podczas przepływu dwufazowego ciecz - ciecz

Witczak S., Wiśniowska J.

Inżynieria i Aparatura Chemiczna

|

2010

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Nr 4

88-89

20

The tetanic depression in unfused tetani of fast motor units in mammalian muscle

Celichowski J.

Biocybernetics and Biomedical Engineering

|

2005

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Vol. 25, no. 4

27-35

EN

Tetanic depression is a phenomenon that limits the force of unfused tetani in contractions evoked at unstable stimulation frequencies. In our experiments this phenomenon was visible in tetani evoked at two frequencies of stimulation: the lower immediately followed by the higher one. The force at the higher stimulation frequency was evidently depressed in relation to the force achieved during the control constant-frequency stimulations. This depression concerned the fast motor units and it was not observed in the slow units. The tetanic depression was initially found in the rat medial gastrocnemius muscle. However, it is not clear whether this phenomenon is specific only to the rat muscle or it concerns all mammals. Therefore, in the subsequent series of experiments, the tetanic depression was investigated in the motor units of the feline medial gastrocnemius, and the effect was also observed in all fast units. The maximum evoked depression exceeded 50% of the control values. Moreover, the analysis of the relationship between the amplitude of the tetanic depression and the degree of the tetanic fusion revealed that the strongest amplitude of depression was observed in the middle-fused tetani (with the fusion index in the range 0.5-0.7). The third experimental series proved that the tetanic depression could be visible in tetani evoked at a progressively increasing frequency of stimulation. Moreover, it was found that the effect of the force decrease could result from the prolongation of only one, the first interpulse interval. The amplitude of this decrease exceeded 20% of the control values. Summarizing, the tetanic depression is a phenomenon influencing the force of unfused tetani of the fast motor units at an increasing stimulation frequency. The depressive effect is present in various species of mammals, probably, including human. The amplitude of the depression depends on the fusion of the tetanic contraction. The physiological significance of tetanic depression is closely related to reduction of the importance of the motoneuronal firing rate.