### Browsing by Subject "physics"

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- ItemOpen AccessThe 2000 year old computer: the antikythera mechanism(2014-09-29) Wolfe, DavidIn 1900 the first ancient marine wreck was discovered in the Mediterranean. It took a century to understand that the most interesting and unique find was a series of small bronze barnacle encrusted fragments. When investigated with sophisticated technology, they turned out to be from an analogue mechanical computer, built about 70 BCE and capable of predicting planetary positions and eclipses of the Sun and the Moon both in the past and the future. Its sophistication is centuries earlier than any mechanism that even began to emulate such a device. How did it work and who could have designed and built it? This double lecture will offer answers to these absorbing questions.
- ItemOpen AccessComputational physics resources - topic 1 - basic Monte Carlo(2013) Wheaton, SpencerA collection of resources (simulations and worksheets) focusing on basic Monte Carlo techniques. These materials are suited for guided-inquiry instruction at the senior undergraduate or honours level.
- ItemOpen AccessDemOnline(2014-09-15) Buffler, Andy; Malahe, MichaelDemOnline is a collection of demonstrations and VPython scripts for use in an introductory physics course. The website catalogues both lecture demonstrations and VPython scripts. The lecture demos section contains descriptions of the setup and execution of various physics experiments, along with screenshots and a reference for finding the equipment in the UCT Physics labs. The VPython scripts section contains scripts that demonstrate various physics concepts.
- ItemOpen AccessFull 3+1 dimensional simulation of the relativistic Boltzmann equation(2021) Grunow, Ernst William; Peshier, AndreRelativistic hydrodynamics has been the tool of choice to simulate the dynamics of the quark-gluon plasma produced in heavy-ion collisions. Despite the success of hydrodynamics, it has several shortcomings stemming from the fact that it assumes a system close to equilibrium. An alternative to hydrodynamics is solving the Boltzmann equation, which describes the evolution of the full distribution function of the system without the close to equilibrium requirement. Large scale simulations using the Boltzmann equation, however, has hitherto proved computationally intractable due to their computational expense. By using a novel algorithm, and leveraging the computational power of graphical processor units, we numerically integrate the Boltzmann equation in the relaxation time approximation.
- ItemOpen AccessGalactic and extragalactic distance scales: Some South African contributions(2005) Feast, MichaelThe work of South African astronomers in establishing and refining methods of measuring the distances of stars and galaxies is reviewed.
- ItemOpen AccessGyromagnetic factors and atomic clock constraints on the variation of fundamental constants(2011) Luo, Feng; Olive, Keith A; Uzan, Jean-PhilippeWe consider the effect of the coupled variations of fundamental constants on the nucleon magnetic moment. The nucleon g-factor enters into the interpretation of the measurements of variations in the fine-structure constant, alpha, in both the laboratory (through atomic clock measurements) and in astrophysical systems (e.g. through measurements of the 21 cm transitions). A null result can be translated into a limit on the variation of a set of fundamental constants, that is usually reduced to alpha. However, in specific models, particularly unification models, changes in alpha are always accompanied by corresponding changes in other fundamental quantities such as the QCD scale, Lambda_QCD. This work tracks the changes in the nucleon g-factors induced from changes in Lambda_QCD and the light quark masses. In principle, these coupled variations can improve the bounds on the variation of alpha by an order of magnitude from existing atomic clock and astrophysical measurements. Unfortunately, the calculation of the dependence of g-factors on fundamental parameters is notoriously model-dependent.
- ItemOpen AccessInvestigating multi-directional inhomogeneous granular suspensions(2019) De Klerk, David; Govender Indresan; Mainza, AubreyGranular flows in rotating drums find many applications in industry, even though the dynamics of their granular media is not fully understood. Several models of granular flow and granular suspensions (where a viscous fluid is present in the voids between the granular particles) have been proposed in the last decade and a half. These models are unified in the way that dimensional analysis is employed to describe bulk properties of the flow in terms of a number of dimensionless parameters. However, applicability to rotating drums has not been demonstrated for many of these models. Furthermore, most studies rely on numerical simulations or experiments of slowly rotating drums that are not easily identified with industrial applications that operate in higher Froude regimes. This thesis presents a series of Positron Emission Particle Tracking (PEPT) experiments and Discrete Element Method (DEM) simulations of rotating drums with a viscous fluid. The three aims of the thesis are, to investigate the use of the Ergodic hypothesis when analysing PEPT data, to test the use of the lubrication approximation in the DEM simulations and to compare results from rotating drums to the latest models of granular rheology and granular suspensions. Two sets of PEPT experiments were carried out with a drum (radius R = 230 mm and length L = 200 mm) which was forced to rotate around its axis. The first series of experiments, used to investigate the use of the ergodic hypothesis, used a fixed rotation rate (Ï‰ = 0.6Ï‰c = 0.6 p g/R) and three different particle sizes (5 mm, 8 mm and 10 mm). A radio labelled tracer particleâ€™s location was recorded for 10 h for each of the three particle sizes. The second series of experiments, intended to test rheology models of dense suspensions and the use of the lubrication approximation in DEM, used 10 mm diameter glass spheres and glycerol/water mixtures in a drum. The second configuration was simulated with DEM using the Hertz-Mindlen contact model for particle-particle interactions. The effect of a viscous force between particles in close proximity to each other was captured by a lubrication approximation. Particle level data from experiments and simulations are transformed to smooth fields by a coarsegraining method which is described in detail. The ergodic assumption (which states that time averages of the PEPT tracer is equivalent to the ensemble average and central to analysing PEPT data) is evaluated using the first series of experiments. It was found that the average velocity can be established after 15 min tracking time, however the solids fraction still shows under sampled regions after tracking for 3 h. Several techniques were used to investigate this, including as PoincarÃ© maps and the global mixing index. A variation on the averaging technique is shown to account for under sampled regions in the solids fraction.
- ItemOpen AccessIsaac Newton and his enemies(2011) Wolfe, DavidLectures by David Wolfe, Emeritus Professor of Physics, University of New Mexico and Director, Oppenheimer Institute for Science and International Co-operation. These audio lectures will be of interest to anyone interested in learning more about Isaac Newton and physics from a historical perspective.
- ItemOpen AccessThe Large Hadron Collider and the physics of elementary particles(2012) Wolfe, DavidThe Large Hadron Collider (LHC) at CERN on the Swiss-French border is designed to search for new physics, a term primarily applied to the appearance of symmetries in nature. These audio lectures will be of interest to anyone interested in learning more about the Large Hadron Collider (LHC).
- ItemOpen AccessMeasurements of Gamow-Teller strength in medium mass nuclei using (p,n) reactions at intermediate energies(1997) Steyn, Douw; Aschman, DavidThe simplicity of the beta decay process makes it a powerful tool for the investigation of the weak interaction and of nuclear structure. The two main operators involved, the Fermi (F) and Gamow-Teller (GT) operators, change just the isospin projection, and the isospin and spin projections of a nucleon respectively. Beta decay studies enable the extraction of the transition matrix elements to high precision. However, most GT transition rates deduced from beta decay measurements turn out to be smaller than the calculated single particle rates [1, 2, 3], a phenomenon that has become known as the quenching of GT strength. Beta decay studies are limited io radioactive nuclei in which the transitions are energetically possible. These are invariably between states of low excitation energy, and are also often relatively weak transitions. In addition, the calculation of the beta decay strengths is model-dependent. The model-dependence and uncertainties would be reduced if larger fractions of the total strength were analysed [4]. It is, however, possible to do so with the use of other probes of spin-isospin strength and to compare the results of these to those of beta decay. One such probe is the zero degree (p,n) reaction at intermediate energies [2, 5, 6]. Such a reaction is not subject to some of the limitations of beta decay in that any desired target nucleus may be probed and that the GT strength function may be investigated up to high excitation energies in the final nucleus. The essential similarity of the transition matrix elements of the two processes allows the measured (p,n) strengths to be converted to beta decay strengths.
- ItemOpen AccessPHY1004W - Matter & Interactions(2014-09-18) Buffler, Andy; Fearick, Roger; Govender, Indresan; Peshier, AndrePHY1004W is a first-year, calculus-based introductory Physics course for Science students intending to continue with second-year Physics. MODERN MECHANICS: Matter and interactions, conservation laws, the momentum principle, atomic nature of matter, conservation of energy, energy in macroscopic systems, energy quantization, multiparticle systems, exploring the nucleus, angular momentum, entropy, kinetic theory of gases, efficiency of engines. ELECTRIC AND MAGNETIC INTERACTIONS: Electric fields, electric potential, magnetic fields, electric circuits, capacitance, resistance, magnetic force, Gauss' law, Ampere's law, Faraday's law, induction, electromagnetic radiation, waves and particles, semiconductor devices.
- ItemOpen AccessPHY1012F(2013) Leigh, GregorFirst year physics lectures covering a wide range of topics, namely: Motion; Kinematics; Vectors; and Kinematics in two dimensions. These lecturer slides are aimed at introdcutory courses for Physics at a university level. These lecture slides contain graphs and visualisations of key physics concepts, as well as problem-solving strategies to help students develop their analytical and mathematical skills. These lecture slides can be used by lecturers looking to supplement their lecture materials with external materials or students looking to improve their knowledge through self-study. 5) Dynamics 6) Circular Motion 7) Momentum 8) Energy 9) Work 10) Rotation
- ItemOpen AccessPHY1023H - Principles of Physics A(2014-09-18) Buffler, Andy; Morrison, AngusPHY1023H is a a first-year, calculus-based introductory course primarily for students on the General Entry for Programmes in Science (GEPS). The first half of this course provides students with the essential tools and skills that are required for dealing successfully with physics at first-year university level. The three broad areas that are covered are (a) mathematical techniques and their relationship with physical phenomena, (b) experimental procedures and (c) communication skills, in particular report writing. The second half of the course covers material similar to that of the first half of PHY1004W. Second semester: Mechanics: vectors, kinematics, dynamics, work, energy power, conservative and non-conservative forces, friction, impulse, momentum, collisions, rotation, rotational dynamics, torque, rotational inertia, rotational energy, angular momentum, static equilibrium, gravitation. Properties of matter: elasticity, elastic moduli, hydrostatics, hydrodynamics. Thermodynamics: temperature, heat, kinetic theory of gases, thermodynamic laws, entropy.
- ItemOpen AccessPHYLAB1 - Course 1 laboratory(2014-09-18) Buffler, Andy; Fearick, RogerThis laboratory course accompanies PHY1004W. A first-year laboratory course based on Modern Mechanics and Electromagnetism.
- ItemOpen AccessPHYLAB2 - Course 2 laboratory(2014-09-18) Fearick, RogerThis is a second year laboratory course that accompanies UCT courses PHY2014F and PHY2015S. The lab focuses on an introduction to computational methods, in support of the Classical and Quantum Mechanics lectures. This lab also explores the use of Python in physics education.
- ItemOpen AccessPython for physics(2014-08-22) Fearick, RogerThis is an introduction to the Python programming language for computational physics. Python is a programming language which is increasingly being used for computation in physics. Python is easy to learn; it is a modern, interpreted, object-oriented language; Python programs are simple, clean and easily readable; and it has a wide range of support packages (or program libraries) useful for numerical computation. This resource is useful for physics and mathematics students looking for open-source programmes to support their work.
- ItemOpen AccessSimulation of the ATLAS ITk strip endcap modules for testbeam reconstruction and analysis(2019) Atkin, Ryan Justin; Yacoob, Sahal; Peterson, Stephen W; Wraight, Kenneth G; Blue, AndrewThe Large Hadron Collider (LHC) is planned to be upgraded to the High Luminosity LHC (HL-LHC), increasing the rate of collisions and producing more particles passing through the detectors. This increased production rate will require upgrades to the detectors in order to cope with the large increase in data collection and radiation as well as improving the tracking and particle reconstruction in the higher occupancy environment. A major upgrade to ATLAS, one of the LHC detectors, will be replacing the current Inner Detector (ID) with a fully silicon semi-conductor based Inner Tracker (ITk). The research and development phase of the ITk requires a simulation of the sensors for performance simulations and testing the sensors in testbeams. The ITk strip end-cap sensors will use radial geometries, however the current testbeam telescope simulation software (AllPix) and reconstruction software (EUTelescope) are designed with cartesian geometries. Presented is the work behind implementing a radial geometry for one of the ITk strip endcap sensors, the R0 module, in the simulation software of Allpix and the reconstruction software of EUTelescope. Included in this work is the simulation of the propagation of the charge deposited in the sensor by the beam. The simulated data, as well as data from the actual EUDET testbeam telescope at DESY, Hamburg are both reconstructed with the same reconstruction software and analysed using the same post-reconstruction software. A comparison of the simulation to experiment is then performed, in particular to study the residuals, efficiency and charge sharing of the R0 module.
- ItemMetadata onlyWhy OER ?(2013) Mitchell, Veronica; Klopper, JuanThis video resource is a valuable contribution to promoting Open Educational Resources (OER) for educators to understand how teaching material can be produced and shared. Dr Juan Klopper's willingness to share his expertise and passion with the wider world is an example of good practice where knowledge is for the public good. This video can be an inspiration to other educators to open up their classrooms and to be a producer of OER. In addition it encourages students to realize the flexibility gained from a flipped classroom approach to learning. Dr Klopper's popular website with YouTube teaching tutorials in Surgery, Mathematics and Physics and video edits has been viewed by over 160,000 people worldwide (August 2013).