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Search results for: BOUNDARY VALUE PROBLEM
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Numerical Study of Turbulent Flow and Heat Transfer of Nanofluids in Pipes
PublicationIn 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
PublicationWe 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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Electroelastic biaxial compression of nanoplates considering piezoelectric effects
PublicationIn 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 Modelling of Forced Convection of Nanofluids in Smooth, Round Tubes: A Review
PublicationA 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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Simulations of the Derecho Event in Poland of 11th August 2017 Using WRF Model
PublicationThis 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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Hydraulic resistance analyses of selected elements of the prototype Stirling engine
PublicationThe 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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Post-critical buckling of truncated conical carbon nanotubes considering surface effects embedding in a nonlinear Winkler substrate using the Rayleigh-Ritz method
PublicationThis 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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Paintings
PublicationThe 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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Influence of nonlinearities on the efficiency and accuracy of FEM calculations on the example of a steel build-up thin-walled column
PublicationDue 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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The role of the One-Belt One-Road initiative in China's exports and global value chains
PublicationResearch background: China is regarded as the “world factory” highly involved in international trade and plays an increasingly important role in the global value chains (GVC). Additionally, the “One-Belt One-Road” (OBOR) initiative was proposed by the Chinese government to further promote China in the international market. Purpose of the article: The article explores the role of the OBOR in China’s exports and global value...
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Density smoothness estimation problem using a wavelet approach
PublicationIn 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
PublicationA 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
PublicationStructural 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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Improving Control Dynamics of PMSM Drive by Estimating Zero-Delay Current Value
PublicationDynamic performance of current control loop still remains crucial for position-, speed-, and torque-controlled drives. In the study, a current loop solution has been designed for field oriented control of permanent magnet synchronous motors (PMSM). It enhances typical PI controller with an estimator of zero-delay current (ZDC) value. The ZDC estimation allows for selecting substantially higher controller gain. It reduces control...
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Problem hałasu drogowego na przykładzie Gdyni
PublicationGłównym zagrożeniem dla klimatu akustycznego w Polsce jak i pozostałych krajów Unii Europejskiej jest hałas drogowy, który dotyka głównie duże aglomeracje miejskie. Oddziałuje on negatywnie na samopoczucie i zdrowie osób narażonych na jago działanie. Artykuł przedstawia ten problem na przykładzie pomiarów hałasu drogowego w Gdyni. W celu wykonania pomiarów równoważnego poziomu dźwięku wybrano dwa punkty pomiarowe zlokalizowane...
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WIELOLEKOOPORNE ZAKAŻENIA CANDIDA - PROBLEM XXI WIEKU!
PublicationW ostatnich latach obserwuje się dramatyczny wzrost zakażeń grzybiczych, których przyczyną są grzyby z rodzaju Candida (C). Większość zakażeń wywoływana jest przez C. albicans, C. glabrata, C. krusei, C. parapsilosis i C. tropicalis. Dotychczas najczęściej stosowanymi lekami przeciwko Candida spp były azole, jednakże ze względu na występowanie naturalnej oporności na te antybiotyki (C. glabrata i C. krusei) coraz częściej azole...
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Redefining The Modifiable Areal Unit Problem Within Spatial Econometrics, The Case of the Scale Problem
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Redefining the Modifiable Areal Unit Problem Within Spatial Econometrics, the Case of the Aggregation Problem
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Stability criteria as constraints in a fleet of ships optimisation problem
PublicationRozwiązano problem dotyczący matematycznej optymalizacji floty statków wielozadaniowych typu rzeka-morze, przeznaczonych dla europejskiej żeglugi przybrzeżnej i eksploatowanych w obszarze Mórz Północnego i Bałtyckiego, na poziomie zadania transportowego za pomocą metod programowania nieliniowego z ograniczeniami. Zaproponowano metodę włączenia istniejących kryteriów skuteczności statków jako ograniczeń w ogólnym modelu optymalizacji...
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Boundary problems for differential equations with advanced arguments
PublicationDyskutowane są zagadnienia brzegowe dla równań różniczkowych z wyprzedzonymi argumentami. Przedstawione są warunki dostateczne istnienia quasirozwiązań i rozwiązań rozważanych zagadnień.
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Conductivity of Fibre Composites with Fractures on the Boundary of Inclusions
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Ordinar differential equations with nonlinear boundary conditions
PublicationPraca dotyczy zwyczajnych równań różniczkowych z nieliniowymi warunkami brzegowymi. Sformułowano warunki dostateczne na istnienie rozwiązania (jedynego lub ekstremalnych) zakładając pewną regularność na prawe strony równania i warunek brzegowy. Warunki brzegowe typu okresowego lub antyokresowego są szczególnymi przypadkami ogólnego warunku dyskutowanego w tej pracy.
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Existence of solutions of differential equations with boundary conditions
PublicationPraca dotyczy równań różniczkowych z liniowym warunkiem brzegowym zależnym od parametru. Podane zostały warunki dostateczne na istnienie rozwiązania powyższego zagadnienia. Przy dowodzie i konstrukcji iteracji monotonicznych zastosowano metodę górnych i dolnych rozwiązań. O prawej stronie zagadnienia zakładano jednostronny warunek Lipschitza.
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Advanced differential equations with nonlinear boundary conditions.
PublicationBadano problemy istnienia rozwiązań dla równań różniczkowych z nielinowymi warunkami brzegowymi. Podano też warunki dostateczne na istnienie rozwiązań ekstremalnych. Przedmiotem badań były również nierówności różniczkowe z wyprzedzonym argumentem.
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The influence of inflation pressure and ambient temperature on the value of the truck tires rolling resistance
PublicationThe articlediscusses the effect of inflation pressure and the ambient temperature on the value of the rolling resistance of truck tires which directly translates into fuel consumption. For this purpose, a series of measurements was made at two ambient temperatures (at 25°C and -15°C), using different pumping pressures.
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The impact of China’s One-Belt One-Road initiative on international trade and global value chains
PublicationThis study examines the potential effects of China’s ‘One-Belt One-Road’initiative (OBOR) on trade flows and global value chain (GVC) connections.The empirical analysis is based on the augmented trade gravity model, which comprises 186 economies and 199 of their partners from 2000 to 2018. We also estimate the gravity model for involvement in GVC (domestic value added in intermediate exports, foreign value added in exports, and...
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Working Conditions in Global Value Chains: Evidence for European Employees
PublicationThis article investigates a sample of almost nine million workers from 24 European countries in 2014 to conclude how involvement in global value chains (GVCs) affects working conditions. We use employer–employee data from the Structure of Earnings Survey merged with industry-level statistics on GVCs based on the World Input-Output Database. Given the multidimensional nature of the dependent variable, we compare estimates of the...
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Analizy ilości i jakości odpływu wód deszczowych i roztopowych z kontrolowanej zlewni zurbanizowanej
PublicationIstotnym problemem Gdańska staje się bezpieczeństwo ekologiczne związane ze spływami miejskimi odprowadzanymi bezpośrednio do wód powierzchniowych, często akwenów użyteczności publicznej. W latach 2011÷2013, Katedra Hydrotechniki Wydziału Inżynierii Lądowej i Środowiska Politechniki Gdańskiej, we współpracy z Wojewódzkim Funduszem Ochrony Środowiska i Gospodarki Wodnej w Gdańsku oraz Gdańskimi Melioracjami, podjęła się wdrożenia...
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Geometrical versus analytical approach in problem solving- an exploatory study
PublicationAbstract. In this study we analyse the geometrical visualization as a part of the process of solution. In total 263 students in the first year of study at three different universities in three different countries (Poland, Slovakia and Spain) were asked to solve four mathematical problems. The analysis of the results of all students showed that geometrical visualization for problems where there is a possibility to choose different ways...
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Calculation of an ultimate load value of a silo with geometric imperfections in the shape of eigenforms
PublicationThe ultimate load value of a silo with initial geometric imperfections was measured. The structure was loaded with wind. Imperfections were assumed as translations of the shell nodes from perfect geometry taken from eigenforms and their combinations. Two variants of the maximum deflection placement with respect to the direction of wind pressure were proposed. The first consists in applying the maximum wind pressure to the element...
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Towards High-Value Datasets Determination for Data-Driven Development: A Systematic Literature Review
PublicationOpen government data (OGD) is seen as a political and socio-economic phenomenon that promises to promote civic engagement and stimulate public sector innovations in various areas of public life. To bring the expected benefits, data must be reused and transformed into value-added products or services. This, in turn, sets another precondition for data that are expected to not only be available and comply with open data principles,...
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Problem wyboru zbiornika retencyjnego
PublicationProblemy związane z optymalnym doborem zbiornika retencyjnego. Zapotrzebowanie na ograniczenie wielkości spływów. Optymalizacja lokalizacji. Funkcja retencji oraz mieszana retencyjno - rozsączająca. Próby wymuszeń. Główne zagrożenia. Warunki posadowienia. Specyfika zbiornika rurowego. Dokumentacja przedprojektowa i projektowa.
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Problem ubóstwa w Polsce
PublicationW publikacji podjęto się omówienia problemu ubóstwa. Wskazano na jego przyczyny oraz przeprowadzono analizę jego funkcjonowania w ujęciu teoretycznym. W kontekście rozważań natury teoretycznej, przeprowadzono analizę ubóstwa w Polsce.
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Mobbing as a problem in management ethics
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Dlaczego problem suburbanizacji? : [Wprowadzenie]
PublicationArtykuł opisuje specyfikę zagadnienia suburbanizacji.zawarto w nimtezy porzemawiające za koniecznością podjęcia tej problemtyki badawczej oraz mozliwewgo spektrum badań.
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Numerical study of turbulent flow and heat transfer of nanofluids in pipes
PublicationIn this work, Nusselt number and friction factor are calculated numerically for turbulent pipe flow (6 000 < Re < 12 000) 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 of Vajjha et al. [1]. Ethylene glycol and water, 60:40 EG/W mass ratio, as base fluid and SiO2 nanoparticles are used as nanofluid...
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Numerical Simulations and Tracer Studies as a Tool to Support Water Circulation Modeling in Breeding Reservoirs
PublicationThe article presents a proposal of a method for computer-aided design and analysis of breeding reservoirs in zoos and aquariums. The method applied involves the use of computer simulations of water circulation in breeding pools. A mathematical model of a pool was developed, and a tracer study was carried out. A simplified model of two-dimensional flow in the form of a biharmonic equation for the stream function (converted into...
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Heat transfer characteristics of hybrid microjet – Microchannel cooling module
PublicationThe paper presents experimental investigation of heat transfer intensification in a microjet–microchannel cooling module. Applied technology takes benefits from two very attractive heat removal techniques. When jets are impinging on the surface, they have a very high kinetic energy at the stagnation point, also in microchannels boundary layer is very thin allowing to obtain very high heat fluxes. Main objective of this paper was...
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Surface Dielectric Barrier Discharge Plasma Actuators
PublicationThis paper presents a part of the works conducted in the Plasmaero European project (task 1.1) on surface dielectric barrier discharge actuators applied to airflow control. The study is divided into several parts. In the first part, the goal is to enhance the electric wind produced by a typical single DBD actuator by optimization of the active electrode shape. For instance, the use of a thin wire instead of a plate air-exposed...
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Parallel Implementation of the Discrete Green's Function Formulation of the FDTD Method on a Multicore Central Processing Unit
PublicationParallel implementation of the discrete Green's function formulation of the finite-difference time-domain (DGF-FDTD) method was developed on a multicore central processing unit. DGF-FDTD avoids computations of the electromagnetic field in free-space cells and does not require domain termination by absorbing boundary conditions. Computed DGF-FDTD solutions are compatible with the FDTD grid enabling the perfect hybridization of FDTD...
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Numerical analysis of mechanical properties of an infill structure used in 3D printings
PublicationThe paper presents results of a numerical analysis focused on an identification of mechanical properties of an element created by using Fused Deposition Modelling additive manufacturing technique (FDM). There is presented a description of technology of the 3D printing, numerical model created by using the finite element method (FEM), as well as some problems referred to estimation of the mechanical properties of the printout. The...
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Damaged plasticity model - seismic analysis of structure of the Petronas Twin Towers (Kuala Lumpur) in Malaysia
PublicationThe article presents numerical simulations for the modelling of seismic impact on the structure of Petronas Twin Towers (Kuala Lumpur) in Malaysia with application of two methods. The Response Spectrum method, in which a spectrum of the structure's responses to an earthquake's impact is generated and the Acceletogram (BETA) method, in which we generate dynamic load in the form of a diagram of the connection between acceleration...
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Numerical Simulations of Seepage in Dikes Using unsaturated and Two-Phase Flow Models
PublicationModeling of water flow in variably saturated porous media, including flood dikes, is often based on the Richards equation, which neglects the flow of pore air, assuming that it remains at constant atmospheric pressure. However, there is also evidence that the air flow can be important, especially when the connectivity between the pore air and atmospheric air is lost. In such cases a full two-phase air-water flow model should be...
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Nonlocalized thermal behavior of rotating micromachined beams under dynamic and thermodynamic loads
PublicationRotating micromachined beams are one of the most practical devices with several applications from power generation to aerospace industries. Moreover, recent advances in micromachining technology have led to huge interests in fabricating miniature turbines, gyroscopes and microsensors thanks to their high quality/reliability performances. To this end, this article is organized to examine the axial dynamic reaction of a rotating...
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Integrated Three-Level Dual-Phase Inverter
PublicationIn view of reducing the number of inverter legs that provide dual-phase, three-level output voltages (as may be needed in an uninterruptible power supply), and that also provide a wide range of output frequencies (as needed in an advanced motor drive system with wide speed ranges), a three-level, dual-phase inverter topology is presented in this paper. Its three-level attribute was based on the F-type inverter topological concept,...
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Multiscale model for blood flow after a bileaflet artificial aortic valve implantation
PublicationCardiovascular diseases are the leading cause of mortality in the world, mainly due to atherosclerosis and its consequences. The article presents the numerical model of the blood flow through artificial aortic valve. The overset mesh approach was applied to simulate the valve leaflets motion and to realize the moving mesh, in the aortic arch and the main branches of cardiovascular system. To capture the cardiac system’s response...
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Material Identification of the Human Abdominal Wall Based On the Isogeometric Shell Model
PublicationThe human abdominal wall is an object of interest to the research community in the context of ventral hernia repair. Computer models require a priori knowledge of constitutive parameters in order to establish its mechanical response. In this work, the Finite Element Model Updating (FEMU) method is used to identify an heterogeneous shear modulus distribution for a human abdominal wall model, which is based on nonlinear isogeometric...
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Free Convection Heat Transfer from Horizontal Cylinders
PublicationThe results of experimental investigation of free convection heat transfer in a rectangular container are presented. The ability of the commonly accepted correlation equations to reproduce present experimental data was tested as well. It was assumed that the examined geometry fulfils the requirement of no-interaction between heated cylinder and bounded surfaces. In order to check this assumption recently published correlation equations...
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Gigantic electro-chemo-mechanical properties of nanostructured praseodymium doped ceria
PublicationSome oxygen defective fluorites are non-Newnham electrostrictors, i.e., the electromechanical response does not depend on their dielectric properties. Here, we show gigantic electrostriction in nanocrystalline 25 mol% praseodymium doped ceria (PCO) bulk ceramics. The material was fabricated with a fieldassisted spark plasma sintering (SPS) process from high-purity nanoscale PCO powders (<20 nm). The SPS process consolidates the...
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Heat transfer intensification by jet impingement – numerical analysis using RANS approach
PublicationJet impingement is a method of the heat transfer enhancement applied in the engineering systems. The idea is to generate fast-flow fluid jet which impinge on the heated (or cooled) surface, causing significantly higher heat transfer rate. Although some flat surface jet impingement cases are described in the literature, the validated data is still limited. The reason is coming from the fact, that these flows are hydrodynamically...