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2. Empirical correlation between the shear-wave velocity and the dynamic probing heavy test : case study, Varaždin, CroatiaStjepan Strelec, Davor Stanko, Mario Gazdek, 2016, izvirni znanstveni članek Opis: Varaždin is located in the north-western part of Croatia in shallow quaternary alluvial sediments of the Drava River basin. Local site effects due to the alluvial soft sediments can play a crucial role in the amplification of seismic-wave ground motions. The shear-wave velocity (VS) is one of the most important parameters for determining dynamic soil properties and ground-response analyses.
The seismic surface wave method (MASW) is the simplest and a very efficient way of measuring the shear-wave velocity in the field. The Dynamic Probing Heavy (DPH) test is suited to determining the soil strength and the soil deformation properties. However, there are a lack of correlations between the shear-wave velocity and the DPH tests (VS - NDPH) in the literature. In this paper we present empirical correlations between the shear-wave velocity VS and the soil penetration resistance NDPH with: a) raw (original) NDPH data: VS = 97.839·NDPH0.395, (R2 = 0.723); b) a groundwater correction NDPH data: VS = 92.998·NDPH0.363 (R2 = 0.815). From the measured DPH data, the shear-wave velocity (VS), the shear modulus (Go) and the Young’s modulus (Eo and Er) were estimated. Two different approaches (low vs. high strain) were compared, and the results were found to be in good agreement when the relative difference between the velocities is small and smooth.
Dynamic probing tests are good for studying a discrete point of interest in a large field area based on preliminary seismic tests. The suggested correlation VS - NDPH can be used for a rough estimation of VS from NDPH (they are site-specific, and so not applicable worldwide). In this way valuable information about dynamic soil properties can be extracted for ground-response analyses and the study of local site effects. Ključne besede: shear-wave velocity, MASW, DPH, empirical correlations, dynamic elastic moduli, dynamic soil properties Objavljeno v DKUM: 15.06.2018; Ogledov: 1850; Prenosov: 87 Celotno besedilo (1,34 MB) Gradivo ima več datotek! Več... |
3. Determination of Vs30 for seismic ground classification in the Ljubljana area, SloveniaJanez Rošer, Andrej Gosar, 2010, izvirni znanstveni članek Opis: The shear modulus, known as Gmax, is a key parameter for predicting the static and dynamic behavior of soils. Its value decreases by increasing the shear strain. This is because of reducing the soil’s stiffness as a result of increasing the shear deformation. The increasing of the shear modulus by increasing the shear strain is affected by some of the soil properties, such as the Void ratio (e), the Over consolidated ratio (OCR), the Normal stress (σ), the Plasticity index (PI), the Water content (ω%), the Shear strain rate, the Soil structure, and the Loading history, etc. In this paper, undrained, direct shear tests were conducted to study the effect of the plasticity index (PI) and the normal stress (σ) on the shear behavior and the shear modulus of remolded clays. The results show that the normalized shear modulus at a constant strain will generally increase as the σ and PI increase, and the common empirical equations for undisturbed soils at γ = 0~0.1 might be applicable for the disturbed soils too. Ključne besede: microtremor survey methods, shear-wave velocity, seismic site effect, microzonation, Eurocode 8 Objavljeno v DKUM: 11.06.2018; Ogledov: 1223; Prenosov: 187 Celotno besedilo (1,07 MB) Gradivo ima več datotek! Več... |
4. Increased augmentation index and central systolic arterial pressure are associated with lower school and motor performance in young adolescentsBernarda Vogrin, Marjan Rupnik, Dušanka Mičetić-Turk, 2017, izvirni znanstveni članek Opis: Objective: In adults, improper arterial function has been linked to cognitive impairment. The pulse wave velocity (PWV), augmentation index (AIx) and other vascular parameters are useful indicators of arterial health. In our study, we monitored arterial properties, body constitution, school success, and motor skills in young adolescents. We hypothesize that reduced cognitive and motor abilities have a vascular origin in children.
Methods: We analysed 81 healthy school children aged 11-16 years. Anthropometry central systolic arterial pressure, body mass index (BMI), standard deviation scores (SDS) BMI, general school performance grade, and eight motor tests were assessed. PWV, AIx, and central systolic arterial pressure (SBPao) were measured.
Results: AIx and SBPao correlated negatively with school performance grades. Extremely high AIx, PWVand SBPao values were observed in 5% of children and these children had average to low school performance. PWV correlated significantly with weight, height, and waist and hip circumference. AIx, PWV, school success, and BMI correlated strongly with certain motor functions.
Conclusions: Increased AIx and SBPao are associated with lower school and motor performance in children. PWV is influenced by the body's constitution. Ključne besede: augmentation index, pulse wave velocity, school success, motor functions, young adolescents, central systolic arterial pressure, body mass index Objavljeno v DKUM: 13.07.2017; Ogledov: 1285; Prenosov: 347 Celotno besedilo (160,29 KB) Gradivo ima več datotek! Več... |
5. Dynamic arc fitting path follower for skid-steered mobile robotsPeter Lepej, Johannes Maurer, Suzana Uran, Gerald Steinbauer, 2015, izvirni znanstveni članek Opis: Many applications, such as surveillance, inspection or search and rescue operations, can be performed with autonomous robots. Our aim is a control of modular autonomous systems in rescue robotics. One of the basic problems with autonomous robotics is the execution part where the control commands (translation and rotational velocities) are produced for mobile bases. Therefore we have focused on this area because there is only a small amount of available path following software for skid-steered mobile robots. Our goal was to develop a velocity controller that could be used for multiple skid-steered mobile bases. We considered differential drive mobile bases such as tracked skid-steering mobile bases. Our approach is based on an arc fitting algorithm, which takes into account the robot constraints and kinematical model. It produces a continuous trajectory where fitting to the given path is adapted based on given parameters. Moreover, we have included orientation angle compensation while the mobile robot is moving and ground inclination compensation. Our rescue robot is described, together with the simulation setup and algorithm implementation. We compared our algorithm to the Hector-based software and curvature velocity approach. The results for the proposed algorithm are shown for the simulation results and the experiment. Ključne besede: mobile robot, arc fitting, path following, velocity control, rescue robot Objavljeno v DKUM: 12.07.2017; Ogledov: 2037; Prenosov: 392 Celotno besedilo (1,43 MB) Gradivo ima več datotek! Več... |
6. Design of Lyapunov based nonlinear velocity control of electrohydraulic velocity servo systemsEdvard Detiček, Nenad Gubeljak, Mitja Kastrevc, 2017, izvirni znanstveni članek Opis: Development of a hydraulically driven process of steel centrifugal die casting industry requires accurate response of position in time. In the frame of preliminary investigations the analysis and control of electrohydraulic velocity servo system is considered in the presence of flow nonlinearities and internal friction. The nonlinear and uncertainty characteristics make the conventional controller not yield to the system high requirements. Two different nonlinear design procedures are employed: feedback linearization and backstepping. It is shown that both these techniques can be successfully used to stabilize any chosen operating point of the system. Additionally, invaluable new insights are gained about the dynamics of the system under consideration. This illustrates that the true potential of constructive nonlinear design lies far beyond the mere task of achieving a desired control objective. All derived results are validated by computer simulation of the nonlinear mathematical model of the system. Ključne besede: computer simulation, electro-hydraulic velocity servo system, integrator backstepping, Lyapunov methods, velocity control Objavljeno v DKUM: 11.07.2017; Ogledov: 1522; Prenosov: 387 Celotno besedilo (1,52 MB) Gradivo ima več datotek! Več... |
7. Using LabVIEW in a flow parameters studyGorazd Bombek, Matej Fike, 2012, objavljeni znanstveni prispevek na konferenci Opis: The results of numerical simulations can be validated experimentally, but usually only the aggregate characteristics are compared. If the aggregate and partial characteristics can be compared at the same time, the level of trust is increased and the physics can be studied in detail. This paper presents a modular measurement system incorporating several devices, including a PIV, traverse system, NI CompactRIO and/or a DAQ, which are synchronized and enable the simultaneous acquisition of aggregate and partial parameters at various sampling frequencies. The modular concept allows for easy configuration and adjustments as needed. The high DI sampling frequency achieved by the CompactRIO system enabled the analysis of trigger delay and significantly increased the AI capability of the PIV system. Ključne besede: flow parameter study, velocity profile, measurements, local partial characteristics Objavljeno v DKUM: 10.07.2015; Ogledov: 1334; Prenosov: 55 Povezava na celotno besedilo |
8. Mixed boundary elements for laminar flowsMatjaž Ramšak, Leopold Škerget, 1999, izvirni znanstveni članek Opis: This paper presents a mixed boundary element formulation of the boundary domain integral method (BDIM) for solving diffusion-convective transport problems. The basic idea of mixed elements is the use of a continuos interpolation polynomial for conservative field function approximation and a discontinuous interpolation polynomial for its normal derivative along the boundary element. In this way, the advantages of continuous field function approximation are retained and its conservation is preserved while the normal flux values are approximated by interpolation nodal points with a uniquely defined normal direction. Due to the use of mixed boundary elements, the final discretized matrix system is overdetermined and a special solver based on the least squares method is applied. Driven cavity, natural and forced convection in a closed cavity are studied. Driven caviaty results at Re=100, 400 and 1000 agree better with the benchmark solution than Finite Element Method of Finite Volume Method results for the same grid density with 21 x 21 degrees of freedom. The average Nusselt number values for natural convection ▫$10^3$▫▫$le$▫Ra▫$le$▫▫$10^6$▫ agree better than 0.1% with benchmark solutions for maximal calculated grid desities 61 x 61 degrees for freedom. Ključne besede: fluid mechanics, incompressible fluid, laminar flow, velocity vorticity formulation, boundary element method, mixed boundary elements Objavljeno v DKUM: 01.06.2012; Ogledov: 2327; Prenosov: 96 Povezava na celotno besedilo |
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10. On new approach to rheological modeling of an electrostatic ash and water - quadratic lawPrimož Ternik, 2002, objavljeni znanstveni prispevek na konferenci Opis: In the paper a new rheological model for an electrostatic ash and water mixture is proposed. The fundamental equation of the rheological model was used to determine the relationship between the shear stress and the shear rate as well as the equation of a velocity profile for the flow through a straight pipe. Experimental results obtained from a capillary viscometer were used as the basis to determine the parameters for the proposed model by the non-linear regression analysis. With the Quadratic law a numerical analysis of a mixture flow through a capillary pipe with the finite volume method was performed. The derived equations for the velocity profile, shear stress and shear rate were validated through a comparison of numerically obtained and theoretical results. Finally, the compariosn between the Quadratic and the Power law is presented. Ključne besede: fluid mechanics, non-Newtonian fluids, mixture of electrofilter ash and water, flow in pipes, capillary pipes, rheological model, velocity profile, shear stress, finite volume method, numerical analysis, quadratic law, power law, mehanika fluidov Objavljeno v DKUM: 01.06.2012; Ogledov: 2434; Prenosov: 46 Povezava na celotno besedilo |