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Search results for: TURBULENT VORTEX
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Experimental analysis on the risk of vortex ventilation and the free surface ventilation of marine propellers
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Vortex cavitation as a source of high level acoustic pressure generated by ship propellers
PublicationPraca przedstawia wyniki badań teoretycznych i eksperymentalnych nad mechanizmami fizycznymi generowania wysokiego ciśnienia akustycznego przez kawitujące wiry wierzchołkowe powstające na śrubach okrętowych
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Investigations of vortex structures in granular materials under earth pressure conditions by DEM
PublicationW artykule pokazano rozwój wirów na poziomie ziarna materiału granulowanego podczas parcia pasywnego piasku na sztywną ściankę przemieszczającą się poziomo. Obliczenia wykonano stosując metodę DEM. Przyjęto 3 różne sposoby wyznaczenia wirów i ich czestotliwości.
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Interval vertex-coloring of a graph with forbidden colors
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Interval Vertex-Coloring of a Graph With Forbidden Colors
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Packing three-vertex paths in a subcubic graph
PublicationW pracy rozważany jest problem pakowania scieżek P3 w grafach podkubicznych, pokazano oszacowania dolne na ilość ścieżek w zależności od stopnia spójności grafu oraz minimalnego stopnia.
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Bounds on the vertex-edge domination number of a tree
PublicationA vertex-edge dominating set of a graph $G$ is a set $D$ of vertices of $G$ such that every edge of $G$ is incident with a vertex of $D$ or a vertex adjacent to a vertex of $D$. The vertex-edge domination number of a graph $G$, denoted by $\gamma_{ve}(T)$, is the minimum cardinality of a vertex-edge dominating set of $G$. We prove that for every tree $T$ of order $n \ge 3$ with $l$ leaves and $s$ support vertices we have $(n-l-s+3)/4...
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EXPERIMENTAL AND NUMERICAL VALIDATION OF THE IMPROVED VORTEX METHOD APPLIED TO CP745 MARINE PROPELLER MODEL
PublicationThe article presents a numerical analysis of the CP745 marine propeller model by means of the improved vortex method and CFD simulations. Both numerical approaches are validated experimentally by comparing with open water characteristics of the propeller. The introduced modification of the vortex method couples the lifting surface approach for the propeller blades and the boundary element method for the hub. What is more, a...
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Laboratorial studies on the seepage impact in open-channel flow turbulence
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Spectral Wave Energy Dissipation due to Under-Ice Turbulence
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Turbulence models impact on the flow and thermal analyses of jet impingement
PublicationAccurate numerical reconstruction of heat and mass transfer processes in particular applications, such a jet impingement, is difficult to obtain even with the use of modern computational methods. In the proposed paper, the flow and thermal phenomena occurring during single minijet impingement on the flat, concave and convex, heated surfaces were considered. Problem of impingement on non-flat surface, still not common and purely...
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Graph Vertex Embeddings: Distance, Regularization and Community Detection
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Lossless Compression of Binary Trees with Correlated Vertex Names
PublicationCompression schemes for advanced data structures have become the challenge of today. Information theory has traditionally dealt with conventional data such as text, image, or video. In contrast, most data available today is multitype and context-dependent. To meet this challenge, we have recently initiated a systematic study of advanced data structures such as unlabeled graphs [1]. In this paper, we continue this program by considering...
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Investigations of vortex-structures in granular bodies based on DEM and Helmholtz-Hodge flow field decomposition
PublicationArtykuł omawia wyniki numeryczne dotyczące struktur wirowych w materiałach granulowanych. Obliczenia wykonano dla stanu pasywnego przemieszczającej się sztywnej ścianki. W symulacjach wykorzystano metodę elementów dyskretnych i dekompozycję Helmholtza/Hodge’a pola prędkości. Struktury wirowe okazały się znakomitym prekursorem lokalizacji odkształceń stycznych w materiałach granulowanych.
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The effect of environmental turbulence on cyber security risk management and organizational resilience
PublicationEven though there is a plethora of research on the role of environmental turbulence in organizational performance in general, little attention has been paid to the effect of environmental turbulence on cyber security risk management and further - organizational resilience. Drawing on the resource-based view and contingency theory, this study investigates how technological and market turbulence influence organizational cyber security...
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Erosion under turbulent slurry flow: An experimental determination of particle impact angle, impact direction, and distribution thereof by image processing
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Packing Three-Vertex Paths in 2-Connected Cubic Graphs
PublicationW pracy rozważano problem rozmieszczanie ścieżek P3 w 2-spójnych grafach 3-regularnych. Pokazano, że w 2-spójnym grafie 3-regularnym o n wierzchołkach można zawsze pokryć 9/11 n wierzchołków przez ścieżki P3; podano także odpowiednie oszacowania górne.
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Human memory enhancement through electrical stimulation in the temporal cortex
PublicationDirect electrical stimulation of the human brain can elicit sensory and motor perceptions as well as recall of memories. Stimulating higher order association areas of the lateral temporal cortex in particular was reported to activate visual and auditory memory representations of past experiences (Penfield and Perot, 1963). We hypothesized that this effect could be used to modulate memory processing. Recent attempts at memory enhancement...
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Interval Edge Coloring of Bipartite Graphs with Small Vertex Degrees
PublicationAn edge coloring of a graph G is called interval edge coloring if for each v ∈ V(G) the set of colors on edges incident to v forms an interval of integers. A graph G is interval colorable if there is an interval coloring of G. For an interval colorable graph G, by the interval chromatic index of G, denoted by χ'_i(G), we mean the smallest number k such that G is interval colorable with k colors. A bipartite graph G is called (α,β)-biregular...
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Acoustic Streaming Induced by Periodic and Aperiodic Sound in a Bubbly Liquid
PublicationThe vortex ow which follows intense sound propagating in a bubbly liquid, is considered. The reasons for acoustic streaming are both nonlinearity and dispersion. That makes streaming especial as compared with that in a Newtonian uid. Conclusions concern the vortex ow induced in a half-space by initially harmonic or impulse Gaussian beam. The vortex ow recalls a turbulent ow with increasing in time number of small-scale vortices...
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Optimization of hydrodynamic vortex separator for removal of sand particles from storm water by computational fluid dynamics
PublicationStorm water treatment has been gradually acknowledged for the removal of pollutants from urban areas using the hydro cyclone separation technique. The separation efficiency of the hydrodynamic vortex separator (HDVS) is a complex phenomenon. With the aim enhance the separation potency of HDVS for storm runoff to get rid of sand particles, the HDVS with different structural configurations was studied by computational fluid dynamics....
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Experimental Study of the Influence of Small Upward Seepage on Open-Channel Flow Turbulence
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Curved Surface Minijet Impingement Phenomena Analysed with ζ-f Turbulence Model
PublicationThe jet impingement phenomenon plays an important role among the heat transfer intensification methods. Very often its application and analyses refer to simple flat surfaces, while there is a lack of information in the literature for cases addressing curved surfaces. In the present work, the single jet impingement on the non-flat (concave and convex) surface is studied for a wide range of geometries, which originate from the mini-jet...
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Hotspot of human verbal memory encoding in the left anterior prefrontal cortex
PublicationBackground: Treating memory and cognitive deficits requires knowledge about anatomical sites and neural activities to be targeted with particular therapies. Emerging technologies for local brain stimulation offer attractive therapeutic options but need to be applied to target specific neural activities, at distinct times, and in specific brain regions that are critical for memory formation. Methods: The areas that are critical...
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Dyfuzyjne spalanie turbulentne metanu w strudze: analiza numeryczna płomienia Sandia D
PublicationDyfuzyjne spalanie turbulentne jest najpowszechniej występującym w zastosowa-niach przemysłowych rodzajem tego procesu. Jednak jego dokładny opis wciąż sprawia trudności i obserwuje się rozwój konkurujących modeli implementowanych w podejściu RANS (Reynolds Averaged Navier Stokes), a współcześnie coraz częściej także w metodzie dużych wirów (LES) o czym świadczą liczne publikacje [13, 16, 18, 21]. W niniejszej pracy przedstawiono...
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Thermal and Hydrodynamic Phenomena in the Stagnation Zone — Impact of the Inlet Turbulence Characteristics on the Numerical Analyses
PublicationOne of the methods of heat transfer enhancement is utilization of the turbulent impinging jets, which were recently applied, for example, in the heat exchangers. Their positive impact on the heat transfer performance was proven, but many questions related to the origin of this impact are still unanswered. In general, the wall-jet interaction and the near-wall turbulence are supposed to be its main reason, but their accurate numerical...
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Multiple jets impingement – numerical analysis by the ζ-f and hybrid VLES turbulence models
PublicationPresented paper summarizes the Authors findings referring to the numerical analyses of the jet impinging phenomena in the case of complex jets configurations in various applications e.g. in the heat exchangers. Multiple jets interference resulting in the cross-flow and the surface curvature are the factors which impose the need of advanced turbulence models utilization. The outcome of the research based on the ζ-f turbulence model...
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3-Methoxytyramine Is the Major Metabolite of Released Dopamine in the Rat Frontal Cortex: Reassessment of the Effects of Antipsychotics on the Dynamics of Dopamine Release and Metabolism in the Frontal Cortex, Nucleus Accumbens, and Striatum by a Simple T
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Maximum vertex occupation time and inert fugitive: recontamination does help [online]
PublicationRozważamy problem przeszukania danego grafu prostego G w celu przechwycenia niewidocznego i leniwego uciekiniera. Parametrem optymalizacyjnym, który minimalizujemy jest maksymalny czas (liczba tur strategii przeszukiwania), podczas których wierzchołek może być strzeżony (okupowany przez strażnika). Strategia monotoniczna to taka, która nie dopuszcza sytuacji, w której uciekinier dociera do wierzchołka, który wcześniej został oczyszczony....
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Minimum vertex ranking spanning tree problem for chordal and proper interval graphs
PublicationW pracy rozważamy problem szukania, dla danego grafu prostego, drzewa spinającego, którego uporządkowana liczba chromatyczna jest minimalna. K.~Miyata i inni dowiedli w [Np-hardness proof and an approximation algorithm for the minimum vertex ranking spanning tree problem,Discrete Appl. Math. 154 (2006) 2402-2410], że odpowiedni problem decyzyjny jest NP-trudny już w przypadku pytania o istnienie uporządkowanego 4-pokolorowania....
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Realizacja algorytmów szyfrowania symetrycznego w układach FPGA Xilinx Virtex II.
PublicationW pracy zaprezentowano realizację algorytmów szyfrowania symetrycznego w układach FPGA firmy Xilinx z najnowszej rodziny Virtex II. Podkreślono zalety użycia układów programowalnych w systemach kryptograficznych w stosunku do układów ASIC oraz rozwiązań programowych. Przedstawiono struktury szyfrów blokowych Rijndael, Serpent i Twofish oraz moduły składowe i sposób ich realizacji w układach FPGA. Porównano architektury przetwarzania...
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Closed-loop stimulation of temporal cortex rescues functional networks and improves memory
PublicationMemory failures are frustrating and often the result of ineffective encoding. One approach to improving memory outcomes is through direct modulation of brain activity with electrical stimulation. Previous efforts, however, have reported inconsistent effects when using open-loop stimulation and often target the hippocampus and medial temporal lobes. Here we use a closed-loop system to monitor and decode neural activity from direct...
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APPLICATION OF RESPONSE SURFACE MODELING FOR OPTIMIZATION AND DETERMINATION OF MALONDIALDIALDEHYDE BY VORTEX-ASSISTED DISPERSIVE LIQUID-LIQUID MICROEXTRACTION AND GC-FID
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Optimization of vortex-assisted supramolecular solvent-based liquid liquid microextraction for the determination of mercury in real water and food samples
PublicationA novel method was developed for sample preparation for spectrophotometric determination of Hg(II) in water and food samples. The method was based on vortex-assisted supramolecular solvent-assisted liquid-liquid microextraction (VA-SUPRASs-LLME). Analytical parameters such as pH, chelating agent, solvent type and volume, vortex time and salting out effect were optimized. Surface and normal probability plots were drawn for the variables...
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INVESTIGATIONS OF QUASI-STATIC VORTEX-STRUCTURES IN 3D SAND SPECIMENS BASED ON DEM AND HELMHOLTZ-HODGE VECTOR FIELD DECOMPOSITION.
PublicationArtykuł omawia wyniki numeryczne dotyczące struktur wirowych w materiałach granulowanych w warunkach 3D. Obliczenia wykonano dla ściskania dwuosiowego. W symulacjach wykorzystano metodę elementów dyskretnych i dekompozycję pola wektorowego wg Helmholtza-Hodge’a Struktury wirowe okazały się znakomitym prekursorem lokalizacji odkształceń stycznych w materiałach granulowanych podczas obciążenia.
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Relationship between vortex structures and shear localization in 3D granular specimens based on combined DEM and Helmholtz-Hodge decomposition.
PublicationRelationship between vortex structures and shear localization in 3D granular specimens based on combined DEM and Helmholtz-Hodge decomposition. Granular Matter, doi:10.1007/s10035-018-0815-0, 2018.
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A cortex-like model for animal recognition based on texture using feature-selective hashing
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Similarities and Differences Between the Vertex Cover Number and the Weakly Connected Domination Number of a Graph
PublicationA vertex cover of a graph G = (V, E) is a set X ⊂ V such that each edge of G is incident to at least one vertex of X. The ve cardinality of a vertex cover of G. A dominating set D ⊆ V is a weakly connected dominating set of G if the subgraph G[D]w = (N[D], Ew) weakly induced by D, is connected, where Ew is the set of all edges having at least one vertex in D. The weakly connected domination number γw(G) of G is the minimum cardinality...
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INFLUENCE OF A VERTEX REMOVING ON THE CONNECTED DOMINATION NUMBER – APPLICATION TO AD-HOC WIRELESS NETWORKS
PublicationA minimum connected dominating set (MCDS) can be used as virtual backbone in ad-hoc wireless networks for efficient routing and broadcasting tasks. To find the MCDS is an NP- complete problem even in unit disk graphs. Many suboptimal algorithms are reported in the literature to find the MCDS using local information instead to use global network knowledge, achieving an important reduction in complexity. Since a wireless network...
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An Experimental and Numerical Study of the Vortces Generated by Hydrofoils
PublicationArtykuł przedstawia wyniki projektu badawczego poświęconego wirom generowanym przez płaty nośne. W części eksperymentalnej wykonano anemometrem laserowym pomiary pól prędkości w poprzecznych przekrojach wirów. W częsci numerycznej przeprowadzono obliczenia używając różnych struktur siatki obliczeniowej i różnych modeli turbulencji. Na podstawie porównania wybrano model turbulencji i strukturę siatki najlepiej odzwieciedlające pole...
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Miejsce logistyki w zarządzaniu strategicznym portem.
PublicationPodwyższenie poziomu zdolności konkurencyjnych portów zarówno w sferze kosztowej jak i jakościowej warunkowane jest aktywnym wprowadzeniem systemów logistycznych do portów morskich. Logistyka wychodzi naprzeciw postępującym zjawiskom integracyjnym w transporcie morsko-lądowym i określa oraz wzmacnia rolę portów w międzynarodowych łańcuchach transportowych, które wychodzą daleko poza port. W opracowaniu przedstawiono koncepcję...
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Design of the setup for testing optical telemetry ranging including turbulence simulator for the Earth-to-satellite communication link
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A rapid spectrofluorimetric method for the determination of malondialdehyde in human plasma after its derivatization with thiobarbituric acid and vortex assisted liquid–liquid microextraction
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Optimization of vortex-assisted hydrophobic magnetic deep eutectic solvent-based dispersive liquid phase microextraction for quantification of niclosamide in real samples
PublicationIn this manuscript, a green and fast vortex-assisted hydrophobic magnetic deep eutectic solvent-based dispersive liquid phase microextraction (VA-HMDES-DLPME) method was developed for the selective extraction and determination of niclosamide in read samples, including rice, medicine tablets, and water samples. Here, hydrophobic magnetic deep eutectic solvents were used as the extracting solvent without requiring any centrifugation...
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Mild poikilocapnic hypoxia increases very low frequency haemoglobin oxygenation oscillations in prefrontal cortex
PublicationBackground: The aim of the study was to investigate the effect of mild cerebral hypoxia on haemoglobin oxygenation(HbO2), cerebrospinal fluid dynamics and cardiovascular physiology. To achieve this goal, four signals were recorded simultaneously: blood pressure, heart rate / electrocardiogram, HbO2 from right hemisphere and changes of subarachnoid space (SAS) width from left hemisphere. Signals were registered from 30 healthy,...
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Mai’a K. Davis Cross, Ireneusz Paweł Karolewski (red.), European-Russian Power Relations in Turbulent Times, University of Michigan Press, Ann Arbor 2021, ss. 311.
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Flow of liquid in flat gaps of the satellite motor working mechanism
PublicationThe article describes the methodology and results of investigations of the flow of oil and HFA-E emulsion in flat gaps of the working mechanism of a satellite motor. The flow of liquid in those gaps is turbulent and not fully developed. The article presents two methods of modelling this flow. Method I makes use of the Darcy-Weisbach formula, while Method II bases on the assumption that in the variable-length gaps the flow is turbulent...
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Temperature, velocity and mean turbulence structure in strongly heated internal gas flows. Comparison of numerical predictions with data
PublicationW pracy przedstawiono symulacje numeryczne przy użyciu szeregu modeli turbulencji celem analizy silnie ogrzewanego przepływu powietrza w pionowych rurach. Obliczenia porównano z danymi eksperymentalnymi. Analizowano modyfikacje pola prędkości, temperatury i turbulencji. W rozpatrywanych warunkach odnotowano silną wrażliwość obliczeń na silnie zmieniające się pole temperatury. Stwierdzono, że analizowane przypadki najlepiej odzwierciedla...
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Local Nusselt number evaluation in the case of jet impingement
PublicationJet impingement still is one of demanding cases regarding computational fluid dynamics, due to its highly turbulent behaviour, with occurrence of turbulent-laminar transition. Even recently developed methods exhibit some drawbacks – RANS based simulations lack accuracy, LES and DNS based ones require too much computational time. Hybrid methods also exist, but their development and validation is in progress. Nevertheless, CFD application...
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Proteome changes in renal cortex and medulla induced by dietary supplementation with inulin‐type fructans in growing pigs
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