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Measurement of CO2 solubility and diffusivity in poly(L-lactide) and poly(D,L-lactide-co-glycolide) by magnetic suspension balance
Elena Markočič, Mojca Škerget, Željko Knez, 2008, izvirni znanstveni članek

Opis: The solubility of supercritical carbon dioxide (scCO2) in poly(l-lactide) and poly(d,l-lactide-co-glycolide) at different temperatures (308, 313 and 323 K) and pressures (10-30 MPa) was measured using a magnetic suspension balance. The solubility data were also used for estimating the binary diffusion coefficients. The results show a good solubility of CO2 in both polymers: up to 43% in poly(l-lactide) and 30% in poly(d,l-lactide-co-glycolide). The diffusion coefficients have high values, which verify the liquid-like solvating properties of scCO2. The diffusion coefficient depends on the quantity of gas already absorbed by the polymer; its values decrease with increasing gas concentration.
Ključne besede: SC CO2, solubility, diffusivity, magnetic suspension balance
Objavljeno: 31.05.2012; Ogledov: 1047; Prenosov: 55
URL Povezava na celotno besedilo

Numerical simulation of dilute particle laden flows by wavelet BEM-FEM
Jure Ravnik, Leopold Škerget, Matjaž Hriberšek, Zoran Žunič, 2008, izvirni znanstveni članek

Opis: A wavelet transform based BEM and FEM numerical scheme was used to simulate laminar viscous flow. The velocity-vorticity formulation of the Navier-Stokes equations was used. The flow simulation algorithm was coupled with a Lagrangian particle tracking scheme for dilute suspensions of massless particles and particles without inertia. The proposed numerical approach was used to simulate flow and particle paths for two test cases: flow over a backward-facing step and flow past a circular cylinder. We present methods of calculating the pressure and stream function field at the end of each time step. The pressure field was used to calculate drag and lift coefficients, which enable qualitative comparison of our results with the benchmark. The stream function enabled the comparison of streamlines and massless particle paths in steady state low Reynolds number value flow fields, and thus provided an estimate on the accuracy of the particle tracking algorithm. Unsteady higher Reynolds number value flows were investigated in terms of particle distributions in vortex streets in the wake of the cylinder and behind the step. Sedimentation of particles without inertia was studied in the flow field behind a backward-facing step at Reynolds number value 5000.
Ključne besede: boundary element method, velocity-vertocity formulation, discrete wavelet transform, Lagrangian particle tracking, backward-facing step, bluff body flow, dilute particle suspension
Objavljeno: 01.06.2012; Ogledov: 1061; Prenosov: 58
URL Povezava na celotno besedilo

Decomposed fuzzy proportional-integral-derivative controllers
Marjan Golob, 2001, izvirni znanstveni članek

Opis: In this paper, several types of decomposed proportional-integral-derivative fuzzy logic controllers (PID FLCs) are tested and compared. An important feature of decomposed PID FLCs are their simple structures. In its simplest version, the decomposed PID FLC uses three one-input one-output inferences with three separate rule bases. Behaviours of proportional, integral and derivative PID FLC parts are defined with simple rules in proportional rule base, integral rule base and derivative rule base. The proposed decomposed PID FLC has been compared with several PID FLCs structures. All PID FLCs have been realised by the same hardware and software tools and have been applied as a real-time controller to a simple magnetic suspension system.
Ključne besede: fuzzy logic control, PID control, decomposed fuzzy system, magnetic suspension system
Objavljeno: 01.06.2012; Ogledov: 1103; Prenosov: 64
URL Povezava na celotno besedilo

Shpetim Lajqi, 2013, doktorska disertacija

Opis: The key goal of doctoral thesis was to conceive, design, optimize, and analyze the suspension and steering systems for a four wheel drive and four wheel steered terrain vehicle. The common characteristic of a terrain vehicle is the greater motion of the wheels in order to protect the vehicle from rollover risk when running over rough terrain. Known suspension and steering systems have serious weaknesses. In order to ensure good driving comfort, efficient driving safety, and higher maneuverability, new principles of suspension and steering systems are proposed. The proposed suspension system has been successfully derived from a classical double wishbone control arm. The control arms are long but both equal. Greater wheel motion has been ensured without reducing driving performance. In order to improve the comfort and safety an optimal active damping force has been determined by the active and semi-active systems. On the basis of comprehensive analysis, active system adequacy has been achieved. The proposed suspension design provides relatively small lateral wheel motion, zero camber angles, and it effectively absorbs the vibrations caused by ground configurations. The goal of the developed steering system for this terrain vehicle was to design a new steering mechanism that would provide maneuverability at low speed and suitable stability at higher speed. This has been ensured by two modes of steering, all wheel steer and front wheel steer. The proposed steering mechanisms conform to Ackermann steering geometry for all modes and situations. A totally new steering concept has been developed. This effective design consists of special pairs of gears, known as’ non-circular gears’.
Ključne besede: Terrain vehicle, suspension system, steering system, four wheels steering
Objavljeno: 18.03.2013; Ogledov: 2173; Prenosov: 268
.pdf Celotno besedilo (13,58 MB)

Design of independent suspension mechanism for a terrain vehicle with four wheels drive and four wheels steeering
Shpetim Lajqi, Stanislav Pehan, Naser Lajqi, Afrim Gjelaj, Jože Pšeničnik, Sašo Emin, 2013, izvirni znanstveni članek

Opis: In this paper a terrain vehicle with four wheels drive and four wheels steer intended to use for recreational purpose is presented. The main purpose is to design the suspension mechanism that fulfills requirements about stability, safety and maneuverability. Nowadays, as well as in the past, the development of the suspension systems of the vehicle has shown greater interest by designers and manufacturers of the vehicles. Research is focused to do a comprehensive study of different available independent suspension system (MacPherson, double wishbone, multi-link) and hence forth develop a methodology to design the suspension system for a terrain vehicle. Few chosen suspension systems are analyzed into the very details in order to find out the optimal design of it. During development process of the suspension system should be considered design constraints and requirements provided in the checklist. Afterwards the simulation results for kinematics analyses of suspension mechanism are performed in Working Model 2D and MATLAB environments. Achieved results are discussed in detail in order to find the best solution that will fulfill pretentious requirement from developed suspension system. All these investigations and reviews related to the suspension system will be exploited in order to obtain the optimal suspension geometry to equip a terrain vehicle, with such system.
Ključne besede: terrain vehicle, design, suspension mechanism, suspension geometry
Objavljeno: 10.07.2015; Ogledov: 660; Prenosov: 39
URL Povezava na celotno besedilo

Designs and optimizations of active and semi-active non-linear suspension systems for a terrain vehicle
Shpetim Lajqi, Stanislav Pehan, 2012, izvirni znanstveni članek

Opis: This paper introduces a design and optimization procedure for active and semi-active non-linear suspension systems regarding terrain vehicles. The objective of this approach is the ability to quickly analyze vehicles' suspension performances resulting from passive, active, or semi-active systems. The vehicle is represented by a mathematical model regarding a quarter of it, and equations for motion are derived and solved by using MATLAB/Simulink. In order to verify the reliability of the derived computer program, a comparison is made with one of the comprehensive commercial software packages. The decision parameters of the active damping device are optimized by using the Hooke-Jeeves method, which is based on non-linear programming. The usefulness of the treated active and semi-active systems on a concrete terrain vehicle is presented and compared with the presented passive systems by analyzing the vehicle's body acceleration, velocity, displacement, and vertical tire force, namely those aspects that directly influence driving comfort and safety.
Ključne besede: terrain vehicles, vehicle design, suspension system, semi-active
Objavljeno: 10.07.2015; Ogledov: 403; Prenosov: 57
URL Povezava na celotno besedilo

Influence of crosslinker and monomer ratio on bead size distribution, swelling and polymer network flexibility of 4-nitrophenylacrylate polymer supports
Irena Pulko, Peter Krajnc, 2005, izvirni znanstveni članek

Opis: Sphere shaped polymer supports with styrene and 4-nitrophenylacrylate as monomers and divinylbenzene (DVB) or ethyleneglycoldimethacrylate (EGDMA) as crosslinkers were prepared by free radical polymerization in suspension medium. Ratio of monomers as well as the crosslinking degree varied in order to test the influences on head size distribution, swelling and polymer network flexibility. The amount of crosslinker had an effect on bead size, average bead diameters being between 10 µm and 35 µm when 5% of crosslinker was applied and between 35 µm and 55 µm when 20% was used. The crosslinking degree also affected swelling in dichloromethane, water, methanol, toluene and acetonitrile, being more intense with lower concentrations of DVB or EGDMA. The flexibility of polymer networkwas investigated using reactions with 1,8-diaminooctane. High degrees of additional crosslinking was observed, namely between 58 and 95% indicating high flexibility of polymer network.
Ključne besede: organic chemistry, polymer supports, 4-nitrophenilacrylate, suspension polimerization, bead size distribution
Objavljeno: 10.07.2015; Ogledov: 858; Prenosov: 73
.pdf Celotno besedilo (510,34 KB)
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Upgrading the Management of Electronic Systems in a Passenger Car
Josip Sučec, 2019, magistrsko delo

Opis: The master's thesis introduces the process of modernizing an older model of a passenger car. The mechanical, electrical and programming solutions were required to upgrade the existing car. Upgrades have been made to improve safety, comfort and performance. The safety upgrades contain the development and implementation of the brake temperature and the tire pressure monitoring system, respectively. The comfort upgrades include the car’s light system and accessory improvements, such as “follow me home” function and automatic window closing. The performance upgrades include installation of racing coilovers and the development of remote damping ratio adjustment system. For the central logic unit, a vehicle specific Android device was installed. It controls the local electronic control units made for each specific task and displays tire pressures and brake temperatures. The Android device communicates with the electromechanical car systems by using several serial buses. The communication protocols and their messages in the original car had to be reverse engineered to establish proper communication among the systems in the upgraded car.
Ključne besede: passenger car, serial buses, reverse engineering, adjustable suspension, sensors
Objavljeno: 02.08.2019; Ogledov: 209; Prenosov: 62
.pdf Celotno besedilo (6,95 MB)

Porous beads from multiple emulsions with thiol-ene polymerisation
Stanko Kramer, 2019, magistrsko delo

Opis: This thesis aims to explain the process of porous bead synthesis. The porous beads were prepared from a multiple emulsion water-in-oil-in-water (W/OW) system. The W/O/W multiple emulsion was made up of a High Internal Phase Emulsion (HIPE (primary emulsion)) and a suspension phase. The HIPE consisted of pentaerythritol tetrakis (3 mercaptopropionate) (TT) in combination with either divinyl adipate (DVA) or trimethylolpropane triacrylate (TMPTA) and an internal phase volume fraction of 80 %. The suspension phase consisted of an aqueous phase with dissolved surfactants which stabilised the secondary emulsion. The surfactants which stabilised the secondary emulsion were polyvinylpyrrolidone K30 (PVP K30) and polyvinylpyrrolidone K90 (PVP K90). The polymerisation was carried out thermally at first for 24 hours and later under UV light and daylight, as the thermally initiated polymerisation was unsuccessful due to coalesence. The beads that were obtained using the photoinitiated polymerisation were porous with a mostly bicontinuous structure and varying diameters. The viscosity of the primary emulsion (HIPE) had the greatest influence on the stability of the entire W/O/W emulsion. By adding more than 5 wt. % of toluene to the primary emulsion, the emulsion broke down and did not successfully polymerise. Another important factor was the ratio of the functional groups in the case of TT-co-TMPTA, which greatly affected the yield and structure of the obtained beads. The diameters of the spherical particles were dependent on the viscosity, monomer ratio and surfactant used in the suspension phase. The inner structure of the beads was mostly bicontinuous with occasional pores that resembled a polyHIPE structure. The obtained beads had a yield of up to 80 % in the case of TT-co-DVA and a yield of up to 90 % in the case of TMPTA-co-DVA
Ključne besede: polyHIPE, thiol-ene, suspension polymerisation, porous beads, HIPE
Objavljeno: 17.09.2019; Ogledov: 131; Prenosov: 42
.pdf Celotno besedilo (3,56 MB)

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