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Wyniki wyszukiwania dla: FREE BOUNDARY PROBLEM
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On thermal stability of piezo-flexomagnetic microbeams considering different temperature distributions
PublikacjaBy relying on the Euler–Bernoulli beam model and energy variational formula, we indicate critical temperature causes in the buckling of piezo-flexomagnetic microscale beams. The corresponding size-dependent approach is underlying as a second strain gradient theory. Small deformations of elastic solids are assessed, and the mathematical discussion is linear. Regardless of the pyromagnetic effects, the thermal loading of the thermal...
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Experimental investigation on straight and u-bend double tube heat exchanger with active and passive enhancement methods
PublikacjaAuthors in this work want to demonstrate the possibility to increase the heat transfer efficiency by using simple wire coil inserts to create turbulent flow in the boundary layer as well as air blowing into the annulus of the pipe. In the study, Wilson plot approach was applied in order to estimate heat transfer coefficients for all heat exchanger (HX) configurations. The study focuses on experimental values of heat transfer coefficient...
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Comparative analysis of different numerical models of a steel radial gate
PublikacjaHydrotechnical structures are important components in water management system and general flooding safety. Their reliability should be ensured since potential damage might lead to catastrophic consequences. Weir gates are considered to be highly vulnerable elements of each hydro power plant, with regard to its dynamic resistance. The aim of the paper is to compare different numerical models and their influence on the results of...
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Mathematical model of pennate muscle
PublikacjaThe purpose of this study is to create a new mathematical model of pennate striated skeletal muscle. This new model describes behaviour of isolated flat pennate muscle in two dimensions (2D) by taking into account that rheological properties of muscle fibres depend on their planar arrangement. A new mathematical model is implemented in two types: 1) numerical model of unipennate muscle (unipennate model); 2) numerical model of...
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Rotor Blade Geometry Optimisation in Kaplan Turbine
PublikacjaThe paper presents the description of method and results of rotor blade shape optimisation. The rotor blading constitutes a part ofturbine flow path. Optimisation consists in selection of the shape that minimises ratio of polytrophic loss. Shape of the blade isdefined by the mean camber line and thickness of the airfoil. Thickness is distributed around the camber line based on the ratio ofdistribution. Global optimisation was done...
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Minimal parameter implicit solvent model for ab initioelectronic-structure calculations
PublikacjaAbstract - We present an implicit solvent model for ab initio electronic-structure calculations which is fully self-consistent and is based on direct solution of the nonhomogeneous Poisson equation. The solute cavity is naturally defined in terms of an isosurface of the electronic density according to the formula of Fattebert and Gygi (J. Comput. Chem., 23 (2002) 662). While this model depends on only two parameters, we demonstrate...
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IDENTIFICATION OF THE INTERFECE OF LATERAL SLIDE BEARINGS
PublikacjaIn the paper, the model of slide bearings of motor engine, the metodology of research on this type of bearings and its results are presented measurement standpoint consisting of main elements of Briggs & Stratton 550 serie 10 T 802 model piston motor engine driven by three phase elektric engine is introduced . On the measurement standpoint are measurements were done, needed for specification...
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Influence of anisotropic stiffness in numerical analyses of tunneling and excavation problems in stiff soils
PublikacjaIn the stiff overconsolidated soil deposits anisotropy influences small and intermediate strain stiffness and hence it has important impact on the results of discplacement preditcions in soil-structure modelling. The authors developed a cross-anisotropic soil model which combines both stress dependent and micro-structural anisotropy. The model is based on the anisotropic hyperelastic kernel for small strain stiffness. Reference...
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Modelling of elastic wave propagation in a bolted joint using a thin layer of shell elements
PublikacjaThere are many mathematical models describing the propagation of elastic waves through the imperfect boundary of two media. They were successfully applied to modelling of high frequency bulk waves and their interaction with local defects. On the other hand, the existing literature models of bolted connections ignore the aspect of imperfect connection between elements. Therefore, this paper presents the concept of application of...
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Billiard in a rotating half-plane
PublikacjaThe main objective of this research is to study the properties of a billiard system in an unbounded domain with moving boundary. We consider a system consisting of an infinite rod (a straight line) and a ball (a massless point) on the plane. The rod rotates uniformly around one of its points and experiences elastic collisions with the ball. We define a mathematical model for the dynamics of such a system and write down asymptotic...
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Effects of subfilter velocity modelling on dispersed phase in LES of heated channel flow
PublikacjaA non-isothermal turbulent flow with the dispersed phase is modelled using the Large Eddy Simulation (LES) approach for fluid, one-way coupled with the equations of point-particle evolution. The channel is heated at both walls and isoflux boundary conditions are applied for fluid. Particle velocity and thermal statistics are computed. Of particular interest are the r.m.s. profiles and the probability density function of particle...
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Bending and buckling formulation of graphene sheets based on nonlocal simple first-order shear deformation theory
PublikacjaThis paper presents a formulation based on simple first-order shear deformation theory (S-FSDT) for large deflection and buckling of orthotropic single-layered graphene sheets (SLGSs). The S-FSDT has many advantages compared to the classical plate theory (CPT) and conventional FSDT such as needless of shear correction factor, containing less number of unknowns than the existing FSDT and strong similarities with the CPT. Governing...
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A finite element analysis of thermal energy inclination based on ternary hybrid nanoparticles influenced by induced magnetic field
PublikacjaThe use of hybrid nanoparticles to improve thermal processes is a key method that has implications for a variety of interventions utilized in many sectors. This paper aimed to look into the impacts of ternary nanoparticles on hyperbolic tangent materials to establish their thermal characteristics. Flow describing equations have been explored in the presence of heat production, non-Fourier heat flux, and an induced magnetic field....
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On a comparison principle and the uniqueness of spectral flow
PublikacjaThe spectral flow is a well-known quantity in spectral theory that measures the variation of spectra about 0 along paths of selfadjoint Fredholm operators. The aim of this work is twofold. Firstly, we consider homotopy invariance properties of the spectral flow and establish a simple formula which comprises its classical homotopy invariance and yields a comparison theorem for the spectral flow under compact perturbations. We apply...
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Under the Fire of Disinformation. Attitudes Towards Fake News in the Ukrainian Frozen War
PublikacjaIn this article, we examine individual attitudes towards fake news in the extreme conditions of a propaganda war, taking into account the complex regional social and historical conditions. For this purpose, within the mobile boundary zone during frozen war in Ukraine, we conducted qualitative research among representatives of generations X and Z (high school teachers and students). Being accustomed to fake news turned out to be...
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On solvability of initial boundary-value problems of micropolar elastic shells with rigid inclusions
PublikacjaThe problem of dynamics of a linear micropolar shell with a finite set of rigid inclusions is considered. The equations of motion consist of the system of partial differential equations (PDEs) describing small deformations of an elastic shell and ordinary differential equations (ODEs) describing the motions of inclusions. Few types of the contact of the shell with inclusions are considered. The weak setup of the problem is formulated...
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The Backbone Coloring Problem for Bipartite Backbones
PublikacjaLet G be a simple graph, H be its spanning subgraph and λ≥2 be an integer. By a λ -backbone coloring of G with backbone H we mean any function c that assigns positive integers to vertices of G in such a way that |c(u)−c(v)|≥1 for each edge uv∈E(G) and |c(u)−c(v)|≥λ for each edge uv∈E(H) . The λ -backbone chromatic number BBCλ(G,H) is the smallest integer k such that there exists a λ -backbone coloring c of G with backbone H satisfying...
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Parallel tabu search for graph coloring problem
PublikacjaTabu search is a simple, yet powerful meta-heuristic based on local search that has been often used to solve combinatorial optimization problems like the graph coloring problem. This paper presents current taxonomy of patallel tabu search algorithms and compares three parallelization techniques applied to Tabucol, a sequential TS algorithm for graph coloring. The experimental results are based on graphs available from the DIMACS...
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The Protein Folding Problem
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Problem powodzi miejskich
PublikacjaZagadnienia związane z powtarzającym się w Polsce zjawiskiem powodzi miejskiej pochodzącej od opadu. Problemy ocen ilościowych. Zagadnienie nadmiernego wpływu przeszłości na podejmowane działania, w efekcie niewłaściwa identyfikacja problemów. Przykład działań podjętych w Gdańsku. Inicjatywa bydgoska.
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The Snow Team Problem
PublikacjaWe study several problems of clearing subgraphs by mobile agents in digraphs. The agents can move only along directed walks of a digraph and, depending on the variant, their initial positions may be pre-specified. In general, for a given subset~$\cS$ of vertices of a digraph $D$ and a positive integer $k$, the objective is to determine whether there is a subgraph $H=(\cV_H,\cA_H)$ of $D$ such that (a) $\cS \subseteq \cV_H$, (b)...
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Two-criteria optimisation problem for ventral hernia repair
PublikacjaTwo-criteria optimisation problem related to laparoscopic ventral hernia repair is formulated in this paper. An optimal implant from a given set and its orientation is sought. The implant is subjected to kinematic extortions due to a patient’s body movement and intra-abdominal pressure. The first criterion of the optimisation problem deals with the reaction force in the implant fastener, while the deflection of the implant constitutes...
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Influence of boundary conditions in calibration chamber
PublikacjaPrzedstawiono wyniki badań modelowych penetracji w komorze kalibracyjnej z zastosowaniem modeli o różnej średnicy. Badania przeprowadzono w piasku średnio zagęszczonym i zagęszczonym przy stałej składowej poziomej naprężenia i przy składowej pionowej naprężenia w gruncie do 400 kPa. Określono wpływ warunków brzegowych na uzyskane wyniki oporu podstawy/oporu stożka lub ostrza dylatometru. Wyznaczono współczynniki korekcyjne oraz...
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On delay differential equations with boundary conditions
PublikacjaPodano warunki na istnienie rozwiązania zagadnienia brzegowego typu opóźnionego, zakładając pewne warunki monotoniczności funkcji występującej po prawej stronie naszego zagadnienia. Pokazano, że dwa ciągi monotoniczne są zbieżne do rozwiązania dokładnego.
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Differential equations with integral boundary conditions
PublikacjaStosuje się metodę iteracji monotonicznych opartą na dolnym i górnym rozwiązaniu. Przy jednostronnym warunku Lipschitza uzyskano pewne wyniki dotyczące rozwiązań zwyczajnych równań różniczkowych z całkowym warunkiem brzegowym. Sformułowano warunki dostateczne na istnienie jedynego rozwiązania (lub rozwiązań ekstremalnych) w pewnym segmencie. Podano przykłady ilustrujące przyjęte założenia.
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Boundary effects on behaviour of granular material
PublikacjaW artykule przedstawiono wyniki symulacji lokalizacji odkształceń w materiałach granulowanych podczas ściskania dwuosiowego. Obliczenia wykonano przy zastosowaniu metody elementów skończonych i mikropolarnego modelu hipoplastycznego. W pracy pokazano wpływ warunków brzegowych na globalne i loklane zachowanie sie materiału.
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Evolutionary Sets of Safe Ship Trajectories: problem dedicated operators
PublikacjaThe paper presents the optimization process of the evolutionary sets of safe ship trajectories method, with a focus on its problem-dedicated operators. The method utilizes a customized evolutionary algorithm to solve a constrained optimization problem. This problem is defined as finding a set of cooperating trajectories (a set is an evolutionary individual) of all the ships involved in the encounter situation. The resulting trajectories...
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Determination of free tyrosine in equestrian supplements by LC–MS/MS and comparison of its quantity with total free amino acids content in view of doping control
PublikacjaThe reports on the probable beneficial impact of tyrosine (TYR) supplementation on performance enhancement have contributed to the growth of interest in TYR in equestrian sports field and related industries, such as the manufacture of dietary and nutritional supplements. In this study, the first attempt to the assessment of horses exposure to TYR during nutritional supplementation was demonstrated by quantification of unbound TYR...
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A construction for the hat problem on a directed graph
PublikacjaA team of n players plays the following game. After a strategy session, each player is randomly fitted with a blue or red hat. Then, without further communication, everybody can try to guess simultaneously his own hat color by looking at the hat colors of the other players. Visibility is defined by a directed graph; that is, vertices correspond to players, and a player can see each player to whom he is connected by an arc. The...
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Free convection of water-Al2O3 nanofluid from horizontal porous coated tube
PublikacjaThe main aim of the present study was to investigate the influence of nanoparticles on heat transfer coefficients during free convection of water-Al2O3 nanofluid from horizontal porous coated tube under atmospheric pressure for nanoparticle concentration of 0.01% by weight. Contrary to published data present study concerns on free convection of nanofluids in extensive, quiescent fluid.
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The Opening of Central and Eastern European Countries to Free Trade: A Critical Assessment
PublikacjaThree decades after the fall of the Berlin wall and one and a half decades after the Big Bang enlargement of the European Union (2004-2007), we revisit contrasting narratives about the benefit of both free trade and the EU enlargement for Central and Eastern European (CEE) countries. We distinguish old, pre-2004 EU countries from CEE countries that joined the EU in 2004-2007, as well as from the CEE countries that have not become...
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Extending loophole-free nonlocal correlations to arbitrarily large distances
PublikacjaQuantum theory allows spatially separated observers to share nonlocal correlations, which enable them to accomplish classically inconceivable information processing and cryptographic feats. However, the distances over which nonlocal correlations can be realized remain severely limited due to their high fragility to noise and high threshold detection efficiencies. To enable loophole- free nonlocality across large distances, we introduce...
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Boundary Value Problems
Czasopisma -
Post-critical buckling of truncated conical carbon nanotubes considering surface effects embedding in a nonlinear Winkler substrate using the Rayleigh-Ritz method
PublikacjaThis research predicts theoretically post-critical axial buckling behavior of truncated conical carbon nanotubes (CCNTs) with several boundary conditions by assuming a nonlinear Winkler matrix. The post-buckling of CCNTs has been studied based on the Euler-Bernoulli beam model, Hamilton’s principle, Lagrangian strains, and nonlocal strain gradient theory. Both stiffness-hardening and stiffness-softening properties of the nanostructure...
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Hydraulic resistance analyses of selected elements of the prototype Stirling engine
PublikacjaThe paper presents the results of simulation tests of hydraulic resistance and temperature distribution of the prototype Stirling alpha engine supplied with waste heat. The following elements were analyzed: heater, regenerator and cooler. The engine uses compressed air as a working gas. Analyses were carried out for three working pressure values and different engine speeds. The work was carried out in order to optimize the configuration...
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Influence of nonlinearities on the efficiency and accuracy of FEM calculations on the example of a steel build-up thin-walled column
PublikacjaDue to the increase of computing capabilities of standard processing units, it is possible to perform complex analyses, considering a number of nonlinearities, such as geometric, material and boundary (contact) even on personal computers. In the paper, the authors have analysed the efficiency and accuracy of standard PC’s FEM calculations performed in Abaqus CAE 2017 software on the example of a critical load assessment of a thin-walled...
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Localized impedance measurements of AA2024 and AA2024-T3 performed by means of AFM in contact mode
PublikacjaPurpose: The purpose of this paper is to present the results of an atomic force microscopy (AFM) based approach to local impedance spectroscopy (LIS) measurement performed on AA2024 and AA2024-T3 aluminium alloys. Design/methodology/approach: AFM-LIS measurements were performed ex-situ without the electrolyte environment, so in fact the electrical not electrochemical impedance was obtained. Findings: Relative local impedance values...
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Electroelastic biaxial compression of nanoplates considering piezoelectric effects
PublikacjaIn the present theoretical work, it is assumed that a piezoelectric nanoplate is connected to the voltage meter which voltages have resulted from deformation of the plate due to in-plane compressive forces whether they are critical buckling loads or arbitrary forces. In order to derive governing equations, a simplified four-variable shear deformation plate theory has been employed using Hamilton’s principle and Von-Kármán...
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Numerical Study of Turbulent Flow and Heat Transfer of Nanofluids in Pipes
PublikacjaIn this work, Nusselt number and friction factor are calculated numerically for turbulent pipe flow (Reynolds number between 6000 and 12000) with constant heat flux boundary condition using nanofluids. The nanofluid is modelled with the single-phase approach and the simulation results are compared with experimental data. Ethylene glycol and water, 60:40 EG/W mass ratio, as base fluid and SiO2 nanoparticles are used as nanofluid...
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Shape-Based Pose Estimation of Robotic Surgical Instruments
PublikacjaWe describe a detector of robotic instrument parts in image-guided surgery. The detector consists of a huge ensemble of scale-variant and pose-dedicated, rigid appearance templates. The templates, which are equipped with pose-related keypoints and segmentation masks, allow for explicit pose estimation and segmentation of multiple end-effectors as well as fine-grained non-maximum suppression. We train the templates by grouping examples...
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Paintings
PublikacjaThe painting as a curtain (...) A contradiction is therefore what constitutes a painting, and ambiguity is its right. As a young artist, I intuitively defined the work of art as a boundary. Over the years that intuition changed into a conviction that the particular form of art which is painting at the same time reveals and hides; it exists at this intersection of functions as a see-through curtain. We don’t know why there are some...
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Some aspects of noise generated by a small ship in the shallow sea
PublikacjaThe passing and underwater moving objects produce the noises of variable intensity, which significantly increase the overall level of noise in the sea. This applies to both the sonic and ultrasonic range. The excessive levels of underwater noise adversely affects the so-called underwater acoustic climate and is the reason why this phenomenon is intensively investigated from the number of years. The results of experimental work...
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Simulations of the Derecho Event in Poland of 11th August 2017 Using WRF Model
PublikacjaThis series contains datasets related to the forecasting of a severe weather event, a derecho, in Poland on 11 August 2017. The simulations were conducted using the Weather Research and Forecasting (WRF) model version 4.2.1 with different initial and boundary conditions of the pressure and model levels derived from 5 global models: Global Forecast System (GFS), Global Data Assimilation System (GDAS), European Centre for Medium-Range...
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Numerical Modelling of Forced Convection of Nanofluids in Smooth, Round Tubes: A Review
PublikacjaA comprehensive review of published works dealing with numerical modelling of forced convection heat transfer and hydrodynamics of nanofluids is presented. Due to the extensive literature, the review is limited to straight, smooth, circular tubes, as this is the basic geometry in shell-and-tube exchangers. Works on numerical modelling of forced convection in tubes are presented chronologically in the first part of the article....
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Reactive extrusion of biodegradable aliphatic polyesters in the presence of free-radical-initiators: A review
PublikacjaNowadays, growing attention is being paid to the environment and sustainability, what fully justified research works focused on modification of biodegradable polymers and their composites. In this field of research reactive extrusion seems to be the most promising approach, which fits well to sustainable development strategy. In In the present work, the in-situ modification of biodegradable aliphatic polyesters and the compatibilization...
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Effect of Temperature and Nanoparticle Concentration on Free Convective Heat Transfer of Nanofluids
PublikacjaA theoretical analysis of the influence of temperature and nanoparticle concentration on free convection heat transfer from a horizontal tube immersed in an unbounded nanofluid was presented. The Nusselt (Nu) number and heat transfer coefficient were parameters of the intensity of the convective heat transfer. For free convection, the Nu number was a function of the Rayleigh (Ra) number and Prandtl (Pr) number. The Rayleigh (Ra)...
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Density smoothness estimation problem using a wavelet approach
PublikacjaIn this paper we consider a smoothness parameter estimation problem for a density function. The smoothness parameter of a function is defined in terms of Besov spaces. This paper is an extension of recent results (K. Dziedziul, M. Kucharska, B. Wolnik, Estimation of the smoothness parameter ). The construction of the estimator is based on wavelets coefficients. Although we believe that the effective estimation of the smoothness...
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GreedyMAX-type Algorithms for the Maximum Independent Set Problem
PublikacjaA maximum independent set problem for a simple graph G = (V,E) is to find the largest subset of pairwise nonadjacent vertices. The problem is known to be NP-hard and it is also hard to approximate. Within this article we introduce a non-negative integer valued functionp defined on the vertex set V(G) and called a potential function of agraph G, while P(G) = max{vinV(G)| p(v)} is called a potential of G. For any graph P(G) <= D(G),...
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Normal-form preemption sequences for an open problem in scheduling theory
PublikacjaStructural properties of optimal preemptive schedules have been studied in a number of recent papers with a primary focus on two structural parameters: the minimum number of preemptions necessary, and a tight lower bound on shifts, i.e., the sizes of intervals bounded by the times created by preemptions, job starts, or completions. These two parameters have been investigated for a large class of preemptive scheduling problems,...
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Stability of free floating ship. Part I
PublikacjaSformułowano problem obliczeń ramion prostujących statku swobodnie pływającego, tj. wzdłużnie zrównoważonego przy każdym kącie przechyłu. Ramiona prostujące są niejednoznaczne w takim wypadku, zależą bowiem od sposobu działania momentu przechylającego. Omówiono dwa przypadki, gdy moment przechylający jest równoległy do płaszczyzny symetrii statku, oraz gdy wykonuje najmniejszą pracę, czyli gdy jest równoległy do głównej osi bezwładności...