Made available in DSpace on 2014-10-09T12:41:03Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:17Z (GMT). No. of bitstreams: 1 04033.pdf: 2633354 bytes, checksum: f9347be894a819791c1c4ebbed150b1e (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

M.B.A. / To determine the factors that influence the foreign exchange hedging practice adopted amongst corporate customers of Standard Corporate and Merchant Bank (SCMB). The objectives of this study are: To achieve the above aim the following research objectives are relevant: To determine the factors influencing the setting of foreign exchange hedging objectives. To investigate the foreign exchange products that are used to achieve the hedging objective. And to determine from corporations if the foreign exchange products used are effective in achieving their hedging objectives.

Motivated by the popularity of marketplace applications over social net works, we study optimal recommendation algorithms for online exchange markets. Examples of such markets include peerflix. corn and readitswapit.co.uk. We model these markets as a social network in which each user has two as sociated lists: The item list, i.e, the set of items the user is willing to give away, and the wish list, i.e., the set of items the user is interested in receiv ing. A transaction involves a user giving an item to another user. Users are motivated to engage in transactions in expectation of realizing their wishes. Wishes may be realized by a pair of users swapping items corresponding to each otherâ s wishes, but more generally by means of users exchanging items through a cycle, where each user gives an item to the next user in a cycle, in accordance with the receiving userâ s wishes. In this thesis, we first consider the problem of how to efficiently gener ate recommendations for item exchange cycles in an online market social network. We consider deterministic and probabilistic models and show that under both models, the problem of determining an optimal set of recommen dations that maximizes the expected value of items exchanged is NP-hard and develop efficient approximation algorithms for both models. Next, we study exchange markets over time and try to optimize usersâ waiting times, and fairness whereby fairness we mean: give higher priority to users who contribute more to the system in addition to maximizing expected value. We show that by introducing the concept of points, average waiting time can be improved by a large factor. By designing a credit system, we try to maxi mize fairness in the system. We show not only is the fairness optimization problem NP-hard, but also inapproximable within any multiplicative factor. We propose two heuristic algorithms, one of which is based on rounding the solution to a linear programming relaxation and the other is a greedy algorithm. For both the one-shot market and the overtime market studied in this thesis, we conduct a comprehensive set of experiments, and explore the performance and also scalability of the proposed algorithms. Our experiments suggest that the performance of our algorithms in practice could be much better than the worst-case performance guarantee factors. / Science, Faculty of / Computer Science, Department of / Graduate

This study sets out to investigate the impact of foreign exchange controls on economic performance of emerging economies and South Africa in particular. Amidst South Africa’s newly established stable political environment and its reintroduction to the global economy, a fierce debate exists on whether some measure of exchange controls are necessary or whether they should be abolished altogether. The debate also extends to the nature of the economic liberalisation process in the removal of exchange controls, either in an instantaneous “big bang” approach or in a gradual manner. The research describes arguments for both the support of exchange controls and their abolition. This includes a description of the path South Africa has adopted and an assessment of the merits of exchange controls. Experience from other emerging economies is investigated and correlated with the South African experience. Results indicated that a gradual approach in the relaxation of exchange controls is recommended and that domestic monetary and fiscal policy and trade reforms first before liberating the capital account. It was found that the intensive use of exchange controls as a means of capital account restriction appears to hinder good economic performance; instead it is recommended to create and maintain an institutional environment in which the investment process can occur and where policy-makers can stimulate investment activity with a consequential elimination of capital flight. / Dissertation (MBA)--University of Pretoria, 2010. / Gordon Institute of Business Science (GIBS) / unrestricted

No description available.

The colloidal fraction is the vital part of a soil. These extremely minute particles determine the nature of the soil and are mainly responsible for its many and varied functions. The most important of these functions is perhaps the ability of the colloids to adsorb and exchange cations, the elements so essential to all organisms as building materials. When pure water is passed through a non-saline. soil, the leachate will contain very few dissolved cations. If, on the other hand, an electrolyte such as a weak solution of sodiun chloride, is passed through the same soil, the leachate will contain considerable quantities of calcium, magnesium and potassiun chlorides as well as much of the original sodium chloride. The number of equivalents of the cations collected will be approximately the same as the number of equivalents of sodium ions added. Sodium ions have displaced some of the calcian, magnesium and potassium ions from the soil. This phenomenon is known as cation exchange. Intro., p. 1.

The object of this research is to further investigate the possiblitiy of resolving racemic bases on an optically active cation exchange resin. Any success in this direction would help to explain the reason for Bunnett and Mark's failure, since the general assumption that selective adsorption of one enantimorph of a racemic compound on an active exchanger should occur has been verified by Grubhofer and Schleith. The work can be conveniently divided into two sections. a) The preparation of optically active cation exchange resins and, b) the use of these as resolving agents. P. 8

In order to increase the current efficiency in copper electrowinning tankhouses, iron can be removed from the electrolyte using ion exchange. While this is a proven technology, very little data is available for the application of this technology to copper electrowinning electrolytes containing antimony and bismuth. The feasibility of utilizing iron ion exchange for the removal of iron from copper electrowinning electrolytes containing antimony and bismuth was studied in the laboratory. A picolylamine, a sulphonated diphosphonic, an aminophosphonic and three sulphonated monophosphonic resins were tested. The picolylamine resin was found to be completely impractical as it loaded high levels of copper. All the phosphonic resins tested loaded an appreciable amount of antimony, however, only the aminophosponic resin loaded an appreciable amount of bismuth. Tests to determine whether or not the sulphonated monophosphonic Purolite 5957 resin would continue to load antimony with time and, hence, reduce the resin's ability to remove iron gave inconclusive results. In the event that the resin's ability to remove iron is hampered due to antimony loading, testing has shown that the resin performance may be restored via a regeneration with a solution containing sulphuric acid and sodium chloride. A case study for the application of this technology to the CVRD Inco CRED plant has shown that, while iron removal by ion exchange is technically feasible, it will upset the plant's acid balance in electrolyte. Therefore, an acid removal process would need to be implemented in tandem with an iron ion exchange system. Additionally, preliminary calculations suggest that a system with a single ion exchange column may have difficulty removing sufficient iron for the CRED design conditions. Therefore, consideration should be given to the possibility of utilizing a two column system (one column loading, one column stripping). / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The aim of this study was to establish whether samples of South African-mined clinoptilolite could be used to remove selected metal cations from aqueous solution. The clinoptilolite samples supplied, (by Pratley SA) were in four different particle sizes. Batch study results revealed a decrease in the initial metal concentration in samples that were in contact with clinoptilolite. The finer particle size clinoptilolite had a greater capacity to remove metal cations from aqueous solution. However, ion-exchange results from atomic absorption analysis showed that the larger particle sizes, removed more magnesium ions. Magnesium was the only ion investigated in this study that was present as an exchangeable ion in the Pratley clinoptilolite chemical formula, (MgCaNa2K2)2.5(AlO2)7(SiO2)30.21H2O. Results from the ion-exchange studies showed that the decreasing order of percentage metal removal at pH 3.00 was as follows: Pb > Ni > Cu > Fe > Mg. The mass of metal ions that accumulated on one gram of clinoptilolite as determined from the isotherms was calculated to be 6.16 mg/g for lead and 0.74 mg/g for copper. Data from the lead equilibrium studies were fitted into Langmuir and Freundlich equations and linear regression was used to calculate linearity coefficients for the isotherms. The results showed that the removal of lead ions by clinoptilolite is complex as both monolayer and multilayer adsorption occurs on a heterogeneous surface.

Exchanging and integrating data that belong to worlds of different vocabularies are two prominent problems in the database literature. While data coordination deals with managing and integrating data between autonomous yet related sources with possibly distinct vocabularies, data exchange is defined as the problem of extracting data from a source and materializing it in an independent target to conform to the target schema. These two problems, however, have never been studied in a unified setting which allows both the exchange of the data as well as the coordination of different vocabularies between different sources. Our thesis shows that such a unified setting exhibits data integration capabilities that are beyond the ones provided by data exchange and data coordination separately. In this thesis, we propose a new setting – called DSE, for Data Sharing and Exchange – which allows the exchange of data between independent source and target applications that possess independent schemas, as well as independent yet related domains of constants. To facilitate this type of exchange, we extend the source-to-target dependencies used in the ordinary data exchange setting which allow the association between the source and the target at the schema level, with the mapping table construct introduced in the classical data coordination setting which defines the association between the source and the target at the instance level. A mapping table construct defines for each source element, the set of associated (or corresponding) elements in the domain of the target. The semantics of this association relationship between source and target elements change with different requirements of different applications. Ordinary DE settings can represent DSE settings; however, we show that there exist DSE settings with particular semantics of related values in mapping tables where DE is not the best exchange solution to adopt. The thesis introduces two DSE settings with such a property. We call the first DSE with unique identity semantics. The semantics of a mapping table in this DSE setting specifies that each source element should be uniquely mapped to at least one target element that is associated with it in the mapping table. ii In this setting, classical DE is one method to perform a data exchange; however, it is not the best method to adopt, since it can not represent exchange applications, that require – as DC applications – to compute both portions as well as complete sets of certain answers for conjunctive queries. In addition, we show that adopting known DE universal solutions as semantics for such DSE settings is not the best in terms of efficiency when computing certain answers for conjunctive queries. The second DSE setting that the thesis introduces with the same property is called DSE with equality semantics. This setting captures interesting meaning of related data in a mapping table. Such semantics impose that each source element in a mapping table is related to a target element only if both elements are equivalent (i.e they have the same meaning). We show in our thesis that this DSE setting differs from ordinary DE settings in the sense that additional information could be entailed under such interpretation of related data. Also, this added information needs to be augmented to both the source instance and the mapping table in order to generate target instances that correctly reflect both in a DSE scenario. In other words, we can say that in such a DSE setting, a source instance and a mapping table can be incomplete with respect to the semantics of the mapping table. We formally define the two aforementioned semantics of a DSE setting and we distinguish between two types of solutions for this setting, named,universal DSE solutions, which contain the complete set of exchanged information, and universal DSE KB-Solutions, which store a portion of the exchanged information with implicit information in the form of a set of rules over the target. DSEKB-Solutions allow applications to compute on demand both a portion and the complete set of certain answers for conjunctive queries. In addition,we define the semantics of conjunctive query answering, and we distinguish between sound and complete certain answers for conjunctive queries and we define the algorithms to compute these efficiently. Finally, we provide experimental results which compare the run times to generate DSE solutions versus DSE KB-solutions, and compare the performance of computing sound and complete certain answers for conjunctive queries using both types of solutions