Desalination is a technique of producing fresh water from the saline water. Industrial desalination of sea water is becoming an essential part in providing sustainable source of fresh water for a large number of countries around the world. Thermal process being the oldest and most dominating for large scale production of freshwater in today¿s world. Multi-Stage Flash (MSF) distillation process has been used for many years and is now the largest sector in the desalination industry. In this work, a steady state mathematical model of Multistage Flash (MSF) desalination process is developed and validated against the results reported in the literature using gPROMS software. The model is then used for further investigation. First, a steady state calcium carbonate fouling resistance model has been developed and implemented in the full MSF mathematical model developed above using gPROMS modeling tool. This model takes into consideration the effect of stage temperature on the calcium carbonate fouling resistance in the flashing chambers in the heat recovery section, heat rejection section, and brine heaters of MSF desalination plants. The effect of seasonal variation of seawater temperature and top brine temperature on the calcium carbonate fouling resistance has been studied throughout the flashing stage. In addition, the total annual operating cost of the MSF process is selected to minimise, while optimising the operating parameters such as seawater rejected flow rate, brine recycle flow rate and steam temperature at different seawater temperature and fouling resistance. Secondly, an intermediate storage between the plant and the client is considered to provide additional flexibility in design and operation of the MSF process throughout the day. A simple polynomial based dynamic seawater temperature and different freshwater demand correlations are developed based on actual data. For different number of flash stages, operating parameters such as seawater rejected flow rate and brine recycle flow rate are optimised, while the total annual operating cost of the MSF process is selected to minimise.The results clearly show that the advantage of using the intermediate storage tank adds flexible scheduling in the MSF plant design and operation parameters to meet the variation in freshwater demand with varying seawater temperatures without interrupting or fully shutting down the plant at any time during the day by adjusting the number of stages. Furthermore, the effect of non-condensable gases (NCG) on the steady state mathematical model of MSF process is developed and implemented in the MSF model developed earlier. Then the model is used to study effect of NCG on the overall heat transfer coefficient. The simulation results showed a decrease in the overall heat transfer coefficient values as NCG concentrations increased. The model is then used to study the effect of NCG on the design and operation parameters of MSF process for fixed water demand. For a given plant configuration (fixed design) and at different seawater and steam temperatures, a 0.015 wt. % of NCG results in significantly different plant operations when compared with those obtained without the presence of NCG. Finally, for fixed water demand and in the presence of 0.015 wt. % NCGs, the performance is evaluated for different plant configurations and seawater temperature and compared with those obtained without the presence of NCG.

Constitutive models that conform to separable KBKZ specification have been shown to fit steady-state strain hardening rheological data in planar and uniaxial elongational flows, but with inaccuracy in the rate of strain hardening. The single parameter Molecular Stress Function model of Wagner [Rheol. Acta, 39 (2000), 97-109] has been shown to accurately fit the rise-rate in experimental data for a number of strain hardening and strain softening materials. We study this models accuracy against the well characterised IUPAC LDPE data, and present a method for full implementation of this model for flow solution which is suitable for incorporating into existing separable KBKZ software. A new method for particle tracking in arbitrarily aligned meshes, which is efficient and robust, is given. The Quadratic Molecular Stress Function (QMSF) model is compared to existing separable KBKZ based models, including one which is capable of giving planar strain hardening; the QMSF is shown to fit experimental rheological and contraction flow data more convincingly. The issue of `negative correction pressures¿ notable in some Doi-Edwards based models is addressed. The cause is identified, and leads to a logical method of calculation which does not give these anomalous results.

No / Modelling played an important role in simulation, optimisation, and control of multi-stage flash (MSF) desalination processes. Top brine temperature (TBT) is one of the many important parameters that affect optimal design and operation of MSF processes. Within the MSF process model, calculation of TBT is therefore important. For a given pressure, TBT is a function of boiling point temperature (BPT) at zero salinity and temperature elevation (TE) due to salinity. In this work, we develop several neural network (NN) based correlations for predicting TE. It is found that the NN based correlations can predict the experimental TE very closely. Also predictions by the NN based correlations were good when TE values, obtained using existing correlations from the literature are compared. Due to advancement of the microcomputer, plant automation becomes reliable means of plant maintenance. NN based correlations (models) can be updated in terms of new sets of weights and biases for the same architecture or for a new architecture reliably with new plant data.

Nuwe kommunikasie- en inligtingstegnologie vorm ’n individu se persepsies en hoe hulle ’n spesifieke organisasie sien. MSF Suid-Afrika se webtuiste (met spesifieke verwysing na die foto’s wat gebruik word op die webtuiste) is een van die kommunikasie- en inligtingstegnologieë wat ’n invloed sal hê op die persepsies van die organisasie se belangegroepe. MSF moet krities dink oor die foto’s wat hulle op hulle webtuiste plaas, aangesien dit moontlik die kommunikasie tussen die vrywilligers en die organisasie, sowel as die persepsies van vrywilligers, kan beïnvloed. Dit is van belang vir MSF om deur die foto’s wat hulle op MSF Suid-Afrika se webtuiste plaas die publiek in te lig oor die omstandighede van die populasie waarbinne die veldwerkers werk. Persepsies rig denke en besluite – problematiese uitdagings kan ontstaan indien hierdie persepsies in kontras staan met die persepsies wat MSF graag wil vorm met die gebruik van foto’s op hulle webtuiste. Die studie fokus vervolgens op die persepsies van potensiële vrywilligers van MSF, met spesifieke fokus op die foto’s gebruik op MSF Suid-Afrika se webtuiste. Die algemene doelstelling van hierdie studie is om vanuit ’n organisasiemediabestuursperspektief te bepaal watter rol foto’s op MSF Suid-Afrika se webtuiste speel in die persepsievorming tydens kommunikasie met potensiële vrywilligers as belangegroep. Die hoof bevindinge van die studie toon dat foto’s ’n rol speel om betekenis by te dra tot kommunikasie met belangegroepe, en dat die impak van die foto’s op MSF se webtuiste ’n rol speel in potensiële vrywilligers se persepsievorming. MSF kan meer fokus op die rol wat foto’s in die kommunikatiewe proses speel. Potensiële vrywilligers het verder aangetoon dat hulle meer persoonlike aandag vanaf MSF wil hê. Daar is ook gevind dat dit van belang is dat MSF se webtuiste visueel aanloklik moet wees en dat die foto’s wat op die webtuiste gebruik word akkuraat en geloofwaardig moet wees. MSF se sukses kan verbeter as hulle meer aandag aan potensiële vrywilligers gee. Respondente het verskillende voorstelle gemaak vir hoe MSF meer vrywilligers kan werf. Die studie dra by tot die belangegroepbestuur tussen MSF Suid- Afrika en hulle potensiële vrywilligers. Dit bied aan MSF Suid-Afrika geleentheid om beter te verstaan wat ’n steekproef van potensiële vrywilligers tans dink van die gebruik van foto’s op hulle webtuiste. / MA (Communication Studies), North-West University, Potchefstroom Campus, 2015

Nuwe kommunikasie- en inligtingstegnologie vorm ’n individu se persepsies en hoe hulle ’n spesifieke organisasie sien. MSF Suid-Afrika se webtuiste (met spesifieke verwysing na die foto’s wat gebruik word op die webtuiste) is een van die kommunikasie- en inligtingstegnologieë wat ’n invloed sal hê op die persepsies van die organisasie se belangegroepe. MSF moet krities dink oor die foto’s wat hulle op hulle webtuiste plaas, aangesien dit moontlik die kommunikasie tussen die vrywilligers en die organisasie, sowel as die persepsies van vrywilligers, kan beïnvloed. Dit is van belang vir MSF om deur die foto’s wat hulle op MSF Suid-Afrika se webtuiste plaas die publiek in te lig oor die omstandighede van die populasie waarbinne die veldwerkers werk. Persepsies rig denke en besluite – problematiese uitdagings kan ontstaan indien hierdie persepsies in kontras staan met die persepsies wat MSF graag wil vorm met die gebruik van foto’s op hulle webtuiste. Die studie fokus vervolgens op die persepsies van potensiële vrywilligers van MSF, met spesifieke fokus op die foto’s gebruik op MSF Suid-Afrika se webtuiste. Die algemene doelstelling van hierdie studie is om vanuit ’n organisasiemediabestuursperspektief te bepaal watter rol foto’s op MSF Suid-Afrika se webtuiste speel in die persepsievorming tydens kommunikasie met potensiële vrywilligers as belangegroep. Die hoof bevindinge van die studie toon dat foto’s ’n rol speel om betekenis by te dra tot kommunikasie met belangegroepe, en dat die impak van die foto’s op MSF se webtuiste ’n rol speel in potensiële vrywilligers se persepsievorming. MSF kan meer fokus op die rol wat foto’s in die kommunikatiewe proses speel. Potensiële vrywilligers het verder aangetoon dat hulle meer persoonlike aandag vanaf MSF wil hê. Daar is ook gevind dat dit van belang is dat MSF se webtuiste visueel aanloklik moet wees en dat die foto’s wat op die webtuiste gebruik word akkuraat en geloofwaardig moet wees. MSF se sukses kan verbeter as hulle meer aandag aan potensiële vrywilligers gee. Respondente het verskillende voorstelle gemaak vir hoe MSF meer vrywilligers kan werf. Die studie dra by tot die belangegroepbestuur tussen MSF Suid- Afrika en hulle potensiële vrywilligers. Dit bied aan MSF Suid-Afrika geleentheid om beter te verstaan wat ’n steekproef van potensiële vrywilligers tans dink van die gebruik van foto’s op hulle webtuiste. / MA (Communication Studies), North-West University, Potchefstroom Campus, 2015

Desalination technology provides fresh water to the arid regions around the world. Multi-Stage Flash (MSF) distillation process has been used for many years and is now the largest sector in the desalination industry. Top Brine Temperature (TBT) (boiling point temperature of the feed seawater in the first stage of the process) is one of the many important parameters that affect optimal design and operation of MSF processes. For a given pressure, TBT is a function of Boiling Point Temperature (BPT) at zero salinity and Temperature Elevation (TE) due to salinity. Modelling plays an important role in simulation, optimisation and control of MSF processes and within the model, calculation of TE is therefore important for each stages (including the first stage, which determines the TBT). Firstly, in this work, several Neural Network (NN) based correlations for predicting TE are developed. It is found that the NN based correlations can predict the experimental TE very closely. Also predictions of TE by the NN based correlations were found to be good when compared to those obtained using the existing correlations from the literature. Secondly, a hybrid steady state MSF process model is developed using gPROMS modelling tool embedding the NN based correlation. gPROMS provides an easy and flexible platform to build a process flowsheet graphically. Here a Master Model connecting (automatically) the individual unit model (brine heater, stages, etc.) equations is developed which is used repeatedly during simulation and optimisation. The model is validated against published results. Seawater is the main source raw material for MSF processes and is subject to seasonal temperature variation. With fixed design the model is then used to study the effect of a number of parameters (e.g. seawater and steam temperature) on the freshwater production rate. It is observed that, the variation in the parameters affect the rate of production of fresh water. How the design and operation are to be adjusted to maintain a fixed demand of fresh water through out the year (with changing seawater temperature) is also investigated via repetitive simulation. Thirdly, with clear understanding of the interaction of design and operating parameters, simultaneous optimisation of design and operating parameters of MSF process is considered via the application MINLP technique within gPROMS. Two types of optimisation problems are considered: (a) For a fixed fresh water demand throughout the year, the external heat input (a measure of operating cost) to the process is minimised; (b) For different fresh water demand throughout the year and with seasonal variation of seawater temperature, the total annualised cost of desalination is minimised. It is found that seasonal variation in seawater temperature results in significant variation in design and some of the operating parameters but with minimum variation in process temperatures. The results also reveal the possibility of designing stand-alone flash stages which would offer flexible scheduling in terms of the connection of various units (to build up the process) and efficient maintenance of the units throughout the year as the weather condition changes. In addition, operation at low temperatures throughout the year will reduce design and operating costs in terms of low temperature materials of construction and reduced amount of anti-scaling and anti-corrosion agents. Finally, an attempt was made to develop a hybrid dynamic MSF process model incorporating NN based correlation for TE. The model was validated at steady state condition using the data from the literature. Dynamic simulation with step changes in seawater and steam temperature was carried out to match the predictions by the steady state model. Dynamic optimisation problem is then formulated for the MSF process, subjected to seawater temperature change (up and down) over a period of six hours, to maximise a performance ratio by optimising the brine heater steam temperature while maintaining a fixed water demand.

Among many seawater desalination processes, the multistage flash (MSF) desalination process is a major source of fresh water around the world. The most costly design and operation problem in seawater desalination is due to scale formation and corrosion problems. Fouling factor is one of the many important parameters that affect the operation of MSF processes. This thesis therefore focuses on determining the optimal design and operation strategy of MSF desalinations processes under fouling which will meet variable demand of freshwater. First, a steady state model of MSF is developed based on the basic laws of mass balance, energy balance, and heat transfer equations with supporting correlations for physical properties. gPROMS software is used to develop the model which is validated against the results reported in the literature. The model is then used in further investigations. Based on actual plant data, a simple dynamic fouling factor profile is developed which allows calculation of fouling factor at different time (season of the year). The role of changing brine heater fouling factor with varying seawater temperatures (during the year) on the plant performance and the monthly operating costs for fixed water demand and fixed top brine temperature are then studied. The total monthly operation cost of the process are minimised while the operating parameters such as make up, brine recycle flow rate and steam temperature are optimised. It was found that the seasonal variation in seawater temperature and brine heater fouling factor results in significant variations in the operating parameters and operating costs. The design and operation of the MSF process are optimized in order to meet variable demands of freshwater with changing seawater temperature throughout the day and throughout the year. On the basis of actual data, the neural network (NN) technique has been used to develop a correlation for calculating dynamic freshwater demand/consumption profiles at different times of the day and season. Also, a simple polynomial based dynamic seawater temperature correlation is developed based on actual data. An intermediate storage tank between the plant and the client is considered. The MSF process model developed earlier is coupled with the dynamic model for the storage tank and is incorporated into the optimization framework within gPROMS. Four main seasons are considered in a year and for each season, with variable freshwater demand and seawater temperature, the operating parameters are optimized at discrete time intervals, while minimizing the total daily costs. The intermediate storage tank adds flexible scheduling and maintenance opportunity of individual flash stages and makes it possible to meet variable freshwater demand with varying seawater temperatures without interrupting or fully shutting down the plant at any-time during the day and for any season. Finally, the purity of freshwater coming from MSF desalination plants is very important when the water is used for industrial services such as feed of boiler to produce steam. In this work, for fixed water demand and top brine temperature, the effect of separation efficiency of demister with seasonal variation of seawater temperatures on the final purity of freshwater for both cleaned and fouled demister conditions is studied. It was found that the purity of freshwater is affected by the total number of stages. Also to maintain the purity of freshwater product, comparatively large number of flash stage is required for fouled demister.

Lors de l’été 1968, des images d’enfants décharnés, souffrant de maladies dues à la malnutrition affluent dans les médias occidentaux. Elles proviennent de la région sud orientale de la Fédération du Nigeria, qui a déclaré son indépendance une année auparavant sous le nom de République du Biafra, où se déroule une guerre civile qui oppose les troupes fédérales aux indépendantistes biafrais. L’émotion suscitée en Occident par les représentations du conflit et de la famine qui l’accompagne engendre la mobilisation de diverses organisations humanitaires, qui mettent sur pied des opérations de secours internationales destinées aux populations civiles. Encore peu étudiées par l’historiographie, la crise du Biafra et les réponses qui y sont apportées par les acteurs occidentaux sont l’objet de cette thèse. La recherche examine tout d’abord comment une guerre civile africaine prend la dimension d’une crise humanitaire internationale. Pour ce faire, elle analyse tant la situation sur place que les acteurs de son internationalisation et ses représentations. Ensuite, afin d’appréhender les opérations de secours dans leur complexité la thèse étudie le processus d’élaboration et le déploiement des réponses occidentales à la crise, ainsi que leur réception au Nigeria dans un contexte post-colonial. Enfin, la thèse questionne les principaux éléments qui ont fait du Biafra un moment charnière de l’histoire de l’humanitaire et met en lumière les reconfigurations des discours et des pratiques de l’aide humanitaire qui s’opèrent à la fin des années 1960. / In the summer of 1968, pictures of emaciated children, suffering from diseases due to malnutrition, poured in western medias. They came from the eastern region of the Federation of Nigeria, which had proclaimed its independence one year before and taken the name of the Republic of Biafra. War and famine that were taking place in the region generated widespread concern in the West, where humanitarian organizations decided to set up international relief operations to help alleviate the suffering of the civilian population. Still understudied by the historiography, the crisis in Biafra and the mobilization of western organizations are the subjects of this PhD. Firstly, the dissertation examines how an African civil war became an international humanitarian crisis. To this purpose, it analyses the situation in the ground, the actors of its internationalization and how it was represented. Secondly, in order to grasp the complexity of humanitarian aid, the dissertation studies the elaboration and the deployment of the relied operations, as well as their reception in Nigeria in a post-colonial context. Finally, the thesis questions why Biafra is usually considered as a turning point in the history of humanitarianism. By so doing, it sheds light on the reconfigurations of the discourses and practices of humanitarian aid that took place in the late 1960’s.

In this dissertation, the problem of planning the motion of m Unmanned Vehicles (UVs) (or simply vehicles) through n points in a plane is considered. A motion plan for a vehicle is given by the sequence of points and the corresponding angles at which each point must be visited by the vehicle. We require that each vehicle return to the same initial location(depot) at the same heading after visiting the points. The objective of the motion planning problem is to choose at most q(≤ m) UVs and find their motion plans so that all the points are visited and the total cost of the tours of the chosen vehicles is a minimum amongst all the possible choices of vehicles and their tours. This problem is a generalization of the wellknown Traveling Salesman Problem (TSP) in many ways: (1) each UV takes the role of salesman (2) motion constraints of the UVs play an important role in determining the cost of travel between any two locations; in fact, the cost of the travel between any two locations depends on direction of travel along with the heading at the origin and destination, and (3) there is an additional combinatorial complexity stemming from the need to partition the points to be visited by each UV and the set of UVs that must be employed by the mission. In this dissertation, a sub-optimal, two-step approach to motion planning is presented to solve this problem:(1) the combinatorial problem of choosing the vehicles and their associated tours is based on Euclidean distances between points and (2) once the sequence of points to be visited is specified, the heading at each point is determined based on a Dynamic Programming scheme. The solution to the first step is based on a generalization of Held-Karp’s method. We modify the Lagrangian heuristics for finding a close sub-optimal solution. In the later chapters of the dissertation, we relax the assumption that all vehicles are homogenous. The motivation of heterogenous variant of Multi-depot, Multiple Traveling Salesmen Problem (MDMTSP) derives form applications involving Unmanned Aerial Vehicles (UAVs) or ground robots requiring multiple vehicles with different capabilities to visit a set of locations.

As water resources are rapidly being exhausted, more and more interest is focused on the desalination of sea water and brackish water. Increasing amounts of fresh water will be required in the future due to the rise in population rates, increasing living standards and the expansion of industrial and agricultural activities. The thesis is concentrated on current issues of treatment of sea water, mainly the desalination based on the distillation principle, in order to develop a unit for seawater treatment. The aim is to develop a compact modular unit for seawater desalinate on based on the implementation and evaluation of experimental tests on the experimental unit. The solution includes an overview of systems for treatment of seawater, a discussion of structural and material aspects of the units, design and manufacture of the experimental unit and confrontation the calculated values with the results of experimental measurements.