Titanium dioxide or titania is applied in paints, in the paper industry, fibbers, cosmetics, sunscreen products, toothpaste, foodstuffs, optical coatings, beam splitters and anti-reflection coatings. It is also used as support catalyst and its use as humidity and high-temperature oxygen sensor is under consideration. These applications are related to its high refractive index, oil absorption, tinting strength and inert chemical properties. Commonly, titania is recovered either by leaching ilmenite with sulphuric acid and subsequently hydrolysing the resulting sulfate solution by boiling. In another process, titanium feedstock is converted into titanium tetrachloride and further oxidised to titanium dioxide. These methods are reportedly time-consuming and environmentally unfriendly. They are also unable to use all existing types of titanium minerals. In this study, a novel process for the extraction of titanium valuables from its minerals is presented. The process entails the roasting of titanium ore with alkaline metal salt. The roasted product is hydrolysed with water and acid, and subsequently reacted with sulphuric acid. Alternatively, the hydrolysed product can be used as feedstock in the chloride process. Roasting at 900°C and using a 2:1 (NaOH:ilmenite) mole ratio proved to be the most efficient in releasing titanium units from its ore. Ternary phases dominate under these conditions. Na0.75Fe0.75Ti0.25O2 was the dominant titanium-bearing phase. NaFeTiO4a ndNa2Fe2Ti3O10 were also present. Whenever the Ti:Fe atom ratio was different from one, the surplus titanium was accommodated in single titanates, mainly Na2TiO3, while iron was accommodated in NaFeO2. In many cases Na8Ti5O14 was also present as a result of Na2TiO3 polymerisation. This is consistent with a fusion period of one hour or more. Shorter fusion periods tended to produce binary phases. Similar results were obtained when lower fusion temperatures were employed, i.e. below 550°C. When anatase reactant was used to resemble an anatase ore, Na2Ti6O3,Na2TiO3, Na8Ti5O14 and Na16Ti10O28 were identified in the products. Optimum recoveries were obtained using a 1:1 NaOH:TiO2 mole ratio, and fusing at 800°C for 2 h. Close to 100% of the titanium was recovered. A one-step leaching process was found to be effective compared with multi-step leaching. The leaching step was found to be dependent on time, solid:liquid ratio and temperature. The optimum conditions for solid:liquid ratio, time and temperature were found to be 0.20, and 15 min at 75°C, respectively. Acidic hydrolysis was controlled by the relative amount of iron and titanium in solution. It was found that less than 1% was dissolved between 3 and 7 in pH units. Higher pH values are recommended, since less acid will be used. Any excess of sulphuric acid in the sulfation step proved to be unnecessary. No significant changes were observed in the amount of dissolved iron and titanium. Therefore the stoichiometric amount can be used in the sulfation process. / Thesis (PhD)--University of Pretoria, 2012. / Chemistry / unrestricted

Ein Weg zur Abschätzung von Schwebstaubkonzentrationen aus Sichtweitenbeobachtungen in einer belasteten Atmosphäre auf der Basis der Sichtweitentheorie nach Koschmieder, 1925 unter Berücksichtigung der Feuchtigkeit wird beschrieben. / An approach for the estimation of concentrations of particulate matter in a polluted atmosphere has been described basing on the view range by the Koschmieder formula under consideration of the relative humidity.

Modelling Polygeneration with Desiccant Cooling System for Tropical(and Sub Tropical) ClimatesAbstractSpace cooling has become a necessity in tropical countries. Maintainingcomfortable indoor conditions in industrial environments incur high energy bills due toheavy dependency on electrically operated air conditioning systems. In order to exploreways and means to improve the energy efficiency and alternative energy resources, afeasibility study was conducted using a transient simulation software TRNSYS toimplement a combined cooling, heating and power system suitable for a tropicalcountry.It is proven from the literature search that desiccant dehumidification inconjunction with evaporative coolers can reduce air conditioning operating costssignificantly since the energy required to power a desiccant cooling system is small andthe source of this required energy can be diverse.(Low exergy heat such as solar, wasteheat and natural gas)This research is conducted to evaluate the performance and applicability ofdesiccant cooling systems under tropical climatic conditions. Two operating modes;ventilation and recirculation modes of solid desiccants based open cycle air conditioningthat use waste heat from a CHP plant are analysed to understand their operatingranges, performances and applicability. The model developed is used to propose asuitable desiccant cooling system for a selected industry environment in Sri Lanka.Preliminary results obtained by a parametric analysis for weather data for Colombo, SriLanka shows 0.95 and 1.02 optimum coefficients of performance for the ventilation andrecirculation modes respectively when heat is available at 85°C. Based on thecomparisons of the analysis it is seen that the desiccant cooling appears to be a logicalsupplement for space cooling applications in tropical climates like Sri Lanka. And for thecase study taken to investigate can be proposed with a desiccant cooling system with ahot water storage as the energy supply and it can maintain a COP of about 0.48 undertropical weather conditions.

The main objective of the research was to study the effect of the Stenotaphrum secundatum and Zoysia japonica grasses on the higher and lower environment temperature and lower relative humidity; the secondary objective was to compare whether the Stenotaphrum secundatum grass has a greater impact on the environment parameters of comfort than the Zoysia japonica species. Six materials were used for the extensive green roof, each one forming a layer of the system, which were placed on the concrete slab and in an upward direction, including: PVC geomembrane, Polyester asphalt carpet, Pumice stone, Planar geodren, Prepared soil with guano, compost, muss, and Substrate. In order to make measurements of the higher and lower ambient temperature, a digital thermometer and lower relative humidity meter was used. Stenotaphrum secundatum and Zoysia japonica were used as grass species, as they were the most representative of the grasses used in extensive green roofs. The experimentation was carried out for 2 months from September to October of 2021, having built 3 modules of 1000x600mm roofs, including 1module of the concrete roof with ceramic covering and 2 modules of extensive green roof with two types of grass: Stenotaphrum secundatum and Zoysia japonica. The readings of the environment temperature and relative humidity of the higher and lower part were taken in six points of each module to have a greater number of representative measurements. The watering of the 2 green roof modules with grass was carried out twice a week, applying 5L of water per module. The results indicate that the Zoysia japonica grass is the one that presents a better behavior before the higher ambient temperature and that the Stenotaphrum secundatum grass behaves better before the lower ambient temperature and lower relative humidity. The conclusions indicate that the Stenotaphrum secundatum grass behaves better temperature and relative humidity; the two grass types exhibit different behavior.

For the past several decades, challenges in the detection and collection of latent prints exposed to harsh environmental conditions have inspired research in pretreatment methods prior to the application of chemical, physical, or optical-based enhancement techniques. Some of the difficulties associated with processing degraded latent prints are attributed to dehydration, alterations in chemical composition, and physical disturbance of ridge detail. This study seeks to investigate the effectiveness of humidity, cyanoacrylate fuming method (CFM), and a reflected ultraviolet imaging system (RUVIS) on the detection and collection of aged latent palmprints. Prints were exposed to air flow and ultraviolet (UV) light for a period of 0 to 28 days, and subsequently treated with either cool or warm humidity and CFM. RUVIS was then utilized to detect and capture friction ridge detail after each treatment step. Improvements in RUVIS detection between treatments were evaluated based on four response factors: minutiae count, percent print recovery, ridge thickness and contrast. By measuring these factors, each latent print photograph was able to be converted to quantifiable data to facilitate statistical analysis of potential differences or improvements between treatments. The results demonstrate that the application of 80% relative humidity successfully revived aged latent palmprints across all factors. The combined effect of humidity followed v by CFM treatment and RUVIS detection was greatest for minutiae count and ridge thickness, while percent print recovery and contrast demonstrated more modest improvements when compared to control prints. Additionally, cool temperature treatments outperformed warm temperature treatments across all factors except contrast. The data therefore suggest that to achieve print rejuvenation and overall improvements in RUVIS detection, combined cool humidity and CFM is more effective than humidity alone. The data also indicate a potential correlation between temperature treatments and latent print age. Warm humidity combined with CFM appeared to best enhance RUVIS images on fresher prints of a few days to one week old, while cool humidity and CFM appeared to maximally enhance RUVIS images on prints of several weeks old.

L'observation de la variabilité de l'humidité dans les basses couches de l'atmosphère peut être réalisée en passant par la mesure du paramètre thermodynamique appelé réfractivité. Les radars météorologiques peuvent mesurer les changements de réfractivité dans la couche limite de l'atmosphère en exploitant la phase des signaux de retour des cibles fixes situées aux alentours. La cartographie de ce paramètre a été mise en place à plusieurs reprises lors de campagne de mesures aux Etats-Unis et en Europe, ce qui a démontré qu'elle est maintenant possible dans un rayon de 30 km autour du radar, avec une résolution temporelle de 15 minutes et une résolution spatiale de 5 km. . Un travail de simulation fait par Besson et al. 2012, à l'origine fait pour étudier les sources d'erreur de repliement de la phase, a permis de montrer que la variabilité de la réfractivité augmente considérablement notamment pendant les après-midi et l'été. Depuis trois ans, le travail mené au LATMOS et à Météo-France a consisté à étudier la possibilité de mesurer les fluctuations à l'échelle hectométrique dans l'atmosphère en utilisant la variabilité de la réfractivité. La première étape de ce travail, basée sur un jeu de données issues des réseaux opérationnels de Météo-France (stations automatiques et radar de Trappes) a permis d'établir un lien clair entre les variabilités à 5 minutes, de la réfractivité radar, et de la réfractivité in-situ.La deuxième étape du travail a consisté à regarder la nature de ce lien à plus petite échelle pour comprendre les limites éventuelles de la mesure. Ainsi, une campagne de mesure, TeMeRAiRE (Test de la Mesure de Réfractivité Atmosphérique par Radar à l'Echelle hectométrique) a été menée durant l'été 2014 sur le site instrumenté du SIRTA. Afin de se placer en conditions contrôlées, deux radars ont été placés en visée fixe et horizontale vers 4 réflecteurs connus. L'échantillonnage temporel était de 0,25s pour BASTA et de 1,5ms pour CURIE. Des stations de mesures in-situ ont également été placées à côtés des cibles. Les premiers résultats montrent que la mesure de réfractivité, et de sa variabilité, est possible aux fréquences utilisées (bande X et bande W), ce qui constitue en soi une première. Nous avons aussi pu démontrer que la différentiation spatiale conduit à une résolution spatiale de l'ordre de 100m, et proposer une explication pour un comportement spécifique, et très localisé, de la réfractivité sur le site du SIRTA. e but est maintenant de regarder, par le biais de comparaisons entre les différents instruments, si la mesure radar de la variabilité de la réfractivité dans un volume d'atmosphère constitue effectivement une mesure locale, et si cette dernière peut donner une information sur l'état turbulent de l'atmosphère et son évolution. / Weather radars can retrieve refractivity changes based on phase variations of stationary targets. These retrievals provide valuable information of moisture in the atmospheric boundary layer along the radar path. Recent work on errors associated with these retrievals has shown that the refractivity variability is stronger during the afternoon and the summer season. This observation has led us to study further the link between the refractivity variability measured by radar and the small scales atmospheric fluctuations. First, we compared the variability of the refractivity retrieved from operational weather radars operating at C-band (5.6 GHz) to the variability of the refractivity directly measured by Automatic Weather Stations (AWS). A strong correlation between the two measurements was shown with a negative bias increasing with range from the radar. The bias is well explained when the variability signal is strong if one considers the model of a frozen turbulence transported by the wind. In winter, the measured variability was weaker and close to quantization noise of the AWS measurements, so it was more difficult to draw thesame conclusions. Overall, we were able to demonstrate qualitatively and quantitatively that the refractivity variability retrieved using the radar observations and measured by AWS stations is due to low-level coherent turbulent structures. Next, in order to obtain information at hectometre’s scales, a dedicated field campaign was conducted at SIRTA atmospheric observatory, near Paris. From June to September 2014 two radars (a 94 GHz W-band and a 9.5 GHz X-band radar) were pointing horizontally toward four corner reflectors aligned along a 700 meters line. Two wind and humidity high frequency measurement towers were deployed near the targets. Inter-comparisons between radar and in-situ refractivity measurement also showed a very good correlation. We finally demonstrated the possibility to compute radar refractivity on the path between two targets separated by 50 to 350 m and used this measure of the local variability of the refractivity to identify boundary processes linked to low level atmospheric turbulence.

For many years seed growers have thought that definite relationships existed between seed production and the weather. When this subject is approached there is little unity of opinion, even among neighboring seed growers. This lack of unity would indicate that growers generally are aware of some cause which affects seed setting, but they are not certain that any particular condition of the weather is the chief contributing factor. Scientific writers1 on the subject are also confident that weather is probably one of the major factors influencing seed production.

La complexité du climat repose en grande partie sur le cycle de l'eau. Dans les tropiques,l'eau atmosphérique est un paramètre clef,60% des précipitations globales ont lieu dans lestropiques. La compréhension du cycle de l'eau atmosphérique à l'échelle globale passe par l'utilisation d'observations satellites. Le satellite franco indien Megha-Tropiques, lancé en 2011, permet d'étudier pour la première fois des observations simultanées de l'humidité et de la pluie. La première partie de la thèse consiste en l'étude de l'impact d'un cyclone sur son environnement. Pour cela, un cas d'étude a été sélectionné (typhon Bopha) et undiagnostique a été réalisé pour étudier la production/ consommation d'humidité et de chaleur dans le typhon. La seconde partie de la thèse consiste en l'étude des relations entre les nuages et l'humidité dans la haute troposphère. Cette étude est réalisée au-dessus de l'océan Indien (entre 2011 et 2014) et au-dessus du Sahel (entre 2012 et 2015). / The complexity of the climate depends largely on the water cycle. In the tropics, atmosphericwater is a key parameter, 60% of global rainfall occurs in the tropics. The understandingof the atmospheric water cycle on a global scale need to use satellite observations. The Indo-French satellite Megha-Tropiques, launched in 2011, allows to study for the _rst time simultaneous observations from moisture and rain. The _rst part of the thesis is the study of the impact of a hurricane on its environment. For this, a case study was selected (Typhoon Bopha) and a diagnosis was performed to study the production / consumption of moisture and heat in the typhoon. The second part of the thesis is the study of the relationshipbetween clouds and humidity in the upper troposphere. This study was conducted over the Indian Ocean (between 2011 and 2014) and over the Sahel (between 2012 and 2015).

The present doctoral thesis engages in an internal environment of wooden buildings. Currently, the specialists endeavour to design and realize this type of buildings as low-energy consuming. In an effort, they minimize the thermal losses by reduction of heat transfer coefficient of external walls and reduction or elimination of their air permeability. Not always structural and technical requirements of this kind of buildings are satisfied and also a sanitary and health protection is not fully sustained. Increase in a relative air humidity of internal environment has a negative impact on moisture in wood and heat insulation in the structure. Then the buildings are exposed to the increased risk of mold infestation. This can cause various health problems such as headache, respiratory diseases, general fatigue or impaired concentration. For the purpose of experimental verification of the internal environment, four wooden houses of medium size were observed in 2010 and 2011. The internal temperature and humidity as well as subjective feelings of the household members were monitored there. For the simulation of the real wooden construction, an application BSim was used. Different states as well as stationary and nonstationary physical processes were simulated by the boundary conditions adjustment. Also the criteria for designing and optimization of living comfort of household members were recommended in the thesis.

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