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Problem 1. Designing a distributed personal medical system
Presenter
Professor Jeff Sanders, African Institute for Mathematical Sciences, South Africa
Problem statement
Can we design a distributed (i.e. de-centralised) system to manage personal medical history?
People expect to be, and are in normal years, far more mobile than ever before. Mobile phones and the web provide the communications and information they need, but national border control, personal ID and health systems remain resiliently conventional in spite of being essential for travel. By comparison currency has been potentially liberated, with the advent of Bitcoin.
Can we do the same for personal health records?
If you're stung by a jellyfish on holiday in northern Queensland, break a leg skiing in the Alps, or catch a virus whilst working in Wuhan, immediate treatment requires knowledge of your medical history, allergies and insurance. Record books are unreliable, easy to lose and to keep with you at all times. Is there some distributed system which allows access to your personal medical information from anywhere in the world? What functionality should it support? What are the ethical requirements of such a design?
- This project begins with a brief survey of centralised versus distributed systems, emphasising the local thinking needed to design a distributed protocol which achieves some global property.
- It then considers the features and functionality desired of a distributed personal medical system, emphasising those not achievable in a conventional system (for instance exploitation of data analytics). Ethics, accountability, and intrusion are important considerations that participants may not be used to addressing.
- A system is designed which incorporates the desired features. Coding is not required, but reasoning about correctness of behaviour of our design is.
A distributed system will be thought of as a `data structure' i.e. as consisting of state on which certain operations are defined, like `Update a record', and `Query a record'. We must decide what `state' the system has in order to be able to express its operations accurately. The first step is to under stand what exactly is a `data structure' and how to describe it using discrete mathematics in the Z notation.
A typical industrial problem requires a solution which optimises some quantity. When an optimal solution is unrealistic an acceptably efficient one is sought. It might be: what standard length of aluminium minimises wasteage over various uses. Or what treatment of the residue of sugar cane, for use in generating electricity all-year round, minimises use of energy. The solution is typically described by differential equations and then constraints are imposed to optimise the solution.
This project is an example of an important family of contemporary problems whichfit that paradigm, but whose solution is, instead of a solution to a differential equation, a design (of optimal or acceptable efficiency). Ingenuity is required to invent the design and mathematics is needed to express it and to show that it functions as desired. The design might enable several robots to coordinate in exploring a mine. It might be for a secure electronic voting system. Or it might be for on-line sales featuring specials that benefit from market data. The mathematics is discrete and straightforward though perhaps unfamiliar.
An implementation (i.e. code) is not sought. Indeed our time will be spent on deciding then expressing features and reasoning about how they would be captured in a design.
Presentation
Modelling Camp 2022 Problem 1 Presentation
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Problem 2: An investigation of some numerical methods for solving singular integral equations with Cauchy-type kernels
Presenter
Dr Mathibele Nchabeleng, Department of Mathematics and Applied Mathematics, University of Pretoria
Problem statement
Integral equations are equations in which some unknown function to be determined appears under one or several integral signs. Integral equations arise in several fields of science and engineering, for example, in elasticity, potential theory, fluid mechanics, biomechanics, approximation theory, plasticity, game theory, queuing theory, medicine, acoustics, heat and mass transfer, economics. There are many types of integral equations. We will focus on Cauchy-type singular integral equations of the first kind. Singular integral equations with Cauchy kernels appear in many practical problems of elasticity, crack theory, wing theory and fluid flow. The aim is to study solutions of simple singular integral differential equations.
Presentation
Modelling Camp 2022 Problem 2 Presentation
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Problem 3: Solitary waves in mixtures of fluid and gas bubbles
Presenter
Professor D P Mason, School of Computer Science and Applied Mathematics, University of the Witwatersrand, Johannesburg
Problem statement
The propagation of solitary pressure waves in bubble-fluid mixtures will be studied. The Korteweg-de Vries equation will be derived for pressure waves propagating in one direction only. The single soliton solution of the Korteweg-de Vries equation will be obtained and analysed. The effect of bubbles on the breadth of the solitary wave will be determined. The two-soliton solution devised by Bergmann, which describes the interaction of two solitons, will be investigated. The solutions will be applied to the propagation of solitary pressure waves in Lake Kivu. Lake Kivu is situated on the boarder between Rwanda and the Republic of the Congo. It is a very deep lake with large quantities of methane and carbon dioxide gases dissolved in the depth of the lake. Methane gas is extracted from the lake and used to generate electricity. Gas eruptions could occur if the gas concentrations become sufficiently high producing a bubble-fluid mixture.
Supporting material
- L van Wijngaarden. On the equations of motion for mixtures of liquid and gas bubbles, J Fluid Mechanics, 33, (1968), 465-474.
- G L Lamb. Elements of soliton theory, John Wiley and Sons, 1980, Ch 1.
Presentation
Graduate Modelling Camp Problem 3 Presentation
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Problem 4: Mathematical Modelling of the Max 2-Cut Problem and Solving the Relaxed Model
Presenter
Professor M Ali, School of Computer Science and Applied Mathematics, University of the Witwatersrand, Johannesburg
Problem statement
The max k-cut problem is a very well-known NH-hard combinatorial optimization problem for which no polynomial time algorithm is currently known. Researchers have been working in two directions: (1) the design of efficient algorithms for solving the problem faster, and (2) the better mathematical modelling of the problem. Much effort has been put into the development of the tighter relaxed mathematical model for quicker solution. We consider the max 2-cut problem. The students will derive the non-linear integer programming model and then learn how to derive a semi-definite relaxation of the non-linear model. The semi-definite program (SDP) is a convex problem for which several software are available. The students will use the problem (in the form of a graph) given in the supporting document and derive its mathematical formulation and SDP relaxation. The students then use SeDumi to solve the relaxed problem and examine the results to see if the optimal solution has been obtained. SeDumi is an open-source software which can be downloaded from the internet. The students can then use their own example and obtain results.
Supporting Material
Mathematical Modelling of the Max 2-Cut Problem and Solving the Relaxed Model
Presentation
Maximum Cut of Graph by Semidefinite Relaxation
Modelling Camp 2022 Problem 4 Presentation
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Problem 5: Detecting oil and gas using sound waves
Presenter
Erick Mubai, School of Computer Science and Applied Mathematics, University of the Witwatersrand, Johannesburg
Problem statement
Sound waves are used to detect structures such as salt domes and seeps at the seafloor. These structures might indicate the presence of oil and gas since they can trap and prevent oil and gas from escaping.
The layers of the seafloor are examined using seismic reflection and refraction. A sound pulse is sent from a ship using an airgun array and the reflected/refracted sound from the seafloor is detected by an array of hydrophones. The detected sound can be used to create three-dimensional image of the seafloor and its layer.
Airguns rapidly release compressed air, forming a bubble. This bubble formation produces a loud sound which can penetrate the seafloor as much as 20-30 km below.
The time it takes the sound to return to the surface of the sea can be used to determine the depth of the seafloor and the thickness of the layers in the seafloor.
The sound waves are refracted as the pass-through different layers of the seafloor. The refracted sound can be used to determine density of the layers.
Possible questions:
- How can the refracted sound be used to calculate the densities of the seafloor layers?
- How can the refracted sound be separated from the reflected sound?
Presentation
Modelling Camp 2022 Problem 5 Presentation
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