The objective of this dissertation is to investigate the factors that influence the design of wide-area wavelength division multiplexing (WDM) optical networks. Wide-area networks are presented as communication networks capable of transporting voice and data communication over large geographical areas. These networks typically span a whole country, region or even continent.The rapid development and maturation of WDM technology over the last decade have been well-received commercially and warrants the development of skills in the field of optical network design.The fundamental purpose of all communication networks and technologies is to satisfy the demand of end-users through the provisioning of capacity over shared and limited physical infrastructure. Consideration of the business aspects related to communications traffic and the grooming thereof are crucial to developing an understanding of customer requirements in terms of the selection and quality of services and applications. Extensive communication networks require complex management techniques that aim to ensure high levels of reliability and revenue generation.An integrated methodology is presented for the design of wide-area WDM optical networks. The methodology harnesses physical, logical, and virtual topologies together with routing and channel assignment (RCA) and clustering processes to enhance objectivity of the design process. A novel approach, based on statistical clustering using the Ward linkage as similarity metric, is introduced for solving the problem of determining the number and positions of the backbone nodes of a wide-area network, otherwise defined as the top level hub nodes of the multi-level network model. The influence of the geographic distribution of network traffic, and the intra/inter-cluster traffic ratios are taken into consideration through utilisation of modified gravity models and novel network node weighting. / Dissertation (MEng)--University of Pretoria, 2005. / Electrical, Electronic and Computer Engineering / unrestricted

Cette thèse est une contribution empirique à l’analyse du commerce des produits alimentaires entre le Cameroun et les pays voisins de la zone CEMAC et le Nigeria. La thèse utilise plusieurs outils économétriques permettant de mieux prendre en compte le niveau de désagrégation des données par produits et paires de marchés agricoles. Le premier chapitre, essentiellement descriptif, présente quelques faits stylisés sur le commerce intra-régional en zone CEMAC. Le deuxième chapitre analyse la contribution des chocs de rente pétrolière dans les pays limitrophes du Cameroun sur leur demande d’importations de produits alimentaires camerounais. En utilisant une variété d’estimateurs appropriés pour les modèles de gravité, les résultats indiquent que la croissance de la rente pétrolière dans la sous-région a favorisé de manière significative, l’expansion des exportationscamerounaises de produits alimentaires. Le troisième chapitre a pour objectif d’apprécier l’existence de ruptures structurelles et le degré d’asymétrie dans le niveau d’intégration des marchés agricoles au Cameroun. Les résultats des estimations des modèles à correction d’erreur avec rupture et asymétriques révèlent l’existence d’une instabilité temporelle récente dans l’intégration des marchés agricoles au Cameroun. De plus, les résultats indiquent que les chocs de prix de certains produits agricoles dans les marchés de consommation répondent de façon asymétrique aux variations des prix des marchés de production. Enfin, le quatrième chapitre utilise un modèle à deux pays pour quantifier le degré d’intégration entre les marchés camerounais et sous-régionaux (Gabon) au prisme d’une analyse de co-mouvement des prix des entre marchés. Les résultats économétriques obtenus à partir d’estimation de modèles vectoriels à correction d’erreur sur données de panel montrent qu’il existe une causalité bidirectionnelle et positive à court et long terme entre les marchés camerounais et gabonais. / This is an empirical contribution to the analysis of the regional integration of agricultural markets in central Africa. The thesis uses several econometric models aimed at taking advantage of the high disaggregation of the data by products and market dyads. The first chapter focuses on recent stylized facts on agricultural trade and food security in Cameroon and in the region. Chapter 2 examines the effect of oil discoveries in neighbor countries on Cameroonian exports of agricultural products within the region. Using a wide range of estimators designed for gravity data, econometric results uncover a positive and significant association between oil discoveries in neighbor regional countries on the demand for Cameroonian agricultural goods. The third chapter tests and discusses the existence of a temporal structural break and the asymmetry in agricultural markets within Cameroon. The econometric results obtained from error correction models allowing for structural break and the asymmetry of shocks show that Cameroonian agricultural markets have become less integrated recently, contributing to the asymmetry in the transmission of shocks from production to consumption markets. Chapter 4 uses a two-country model to provide an international evidence of the integration of agricultural markets in central Africa. The framework consists in estimating vector error correction models usingpanel data to test the causality between product prices between the two countries. The results highlight the existence of a bi-directional causality in both the short and long-run.

This thesis concerns about the effectiveness of sanctions imposed between Russia and the EU in 2014. Firstly are conducted theoretical foundations of sanctions and their imposition from the EU as well as Russian contra-sanctions. Secondly, the analysis is based on the gravity model in trade in log-linear form and further develop out-of-sample estimations about trade potentials. Although trade potentials did not proved the expected decrease in exports from EU to Russia, the Input-Output analysis of impacts on exports of food products did so. Results yielded calculated impacts on GDP of various countries due to food embargo that are more or less comparable with the actual evolution of GDP and trade flows. Thirdly, the indirect effects of sanctions of third country effect and re-exports are observed from trade patterns. There has been recorded increased exports of food related products from the EU towards members of Euroasian Customs Union as well as increased imports from these countries to Russia. Finally, the results points out decreased economic activity of Russia due to depreciation of domestic currency, capital flight, decline in oil prices and also sanctions adding up to the problems the economy deals with. The economic impacts of sanctions are present in both parties. However, from the political view sanctions did not proved to be effective so far. Russian intervention in Ukraine territory is continuing.

Cette thèse adopte une approche analytique interrégionale de trois régions économiques pour évaluer les connaissances productives et la diplomatie dans le contexte d’intégration régionale, et en parallèle, les déterminants de la création d'entreprises. Du point de vue de l'intégration européenne, nous introduisons une nouvelle méthodologie de contrôle synthétique pour évaluer l'impact de l'adhésion à l'UE sur l'indice de complexité économique des nouveaux États membres d'Europe centrale et orientale. Nos résultats indiquent que l'adhésion à l'UE a joué un rôle catalyseur pour la connaissance productive des pays portant de faibles niveaux de complexité avant l'adhésion, permettant un taux de développement plus élevé dans la sophistication de l'espace d'exportation de leurs produits. En élargissant notre analyse à tous les pays européens et aux États d’Afrique du Nord, nous procédons dans un deuxième temps à l’analyse des déterminants du commerce des infrastructures institutionnelles et logistiques en élargissant le modèle de Gravité pour y incorporer des éléments de diplomatie (notamment la présence d’ambassades et d’ambassadeurs). Nos résultats démontrent les avantages des infrastructures immatérielles et matérielles ainsi que de l'activité diplomatique sur le commerce bilatéral des PECO et de l'Afrique du Nord, confirmant l'importance de ces variables en tant que moteurs de l'intégration régionale. Dans une dernière partie, nous concentrons notre analyse sur Fédération de Russie en tant que région géographique en introduisant une régression panel des déterminants de l’entrée et de la sortie d’entreprises. Cette évaluation empirique conclut que les défaillances institutionnelles et l’environnement politico-économique ont des effets significatifs sur la création et la destruction d’entreprises russes, avec une estimation robuste du prix mondial du pétrole (quelle que soit la différence entre les régions cibles) suggérant une forte exposition de chaque région russe à une crise mondiale. / This thesis takes a cross-regional analytical approach of three distinct economic areas to evaluate productive knowledge and diplomacy in the context of regional integration alongside determinants of business creation. From the angle of European integration, we introduce a new synthetic control methodology to evaluate the impact of EU accession on the economic complexity index of new CEE member states its results indicating that accession to the EU acted as a catalyst for the productive knowledge of countries with low levels of complexity before accession, allowing a higher rate of development in the sophistication of their product export space. Expanding our analysis to include all European countries and North African states, we proceed in a second stage to analyse institutional and logistical infrastructure determinants of trade by extending the traditional Gravity model to incorporate elements of diplomacy (including the presence of embassies and ambassadors). Our results demonstrate the benefits of soft and hard infrastructure as well as diplomatic activity on the bilateral trade fixed effect CEE and North African countries, validating their importance of these variables as powerful drivers of regional integration. In a final part, we turn our analysis to the Russian Federation as a regional geography with a panel regression analysis of the determinants of firm entry and exit. The empirical evaluation concludes that institutional failures and the politico-economic environment exhibit statistically significant and economically meaningful effects both on the creation and destruction of Russian firms, with a robust estimate of the world oil price (irrespective of the difference in target regions) suggesting a possible high exposure of each Russian region to a global crisis.

In view of the postponement of negotiations for the modernization of the EU-Turkey customs union, this paper is aimed to look back and examine the ex-post impacts of the CU by examining its trade creation and diversion effects. The study tests effects of 44 countries (including Turkey, 28 EU and 15 non-EU countries) with aggregated data for time period from 1989 to 2019 and disaggregated sectoral trade data from 1995 to 2019. For estimation, the gravity model with strong theoretical and empirical foundation is used by combining various fixed effects with PPML method. The results from the aggregated analysis confirm the trade-promoting effects of the EU-Turkey customs union with mixed effects on both trade within the members (intra-trade creation effects) and trade with non- members (extra-trade creation effects). But the trade diversion is not significantly proved in the model. Besides, a substantial heterogeneity in the CU effect is found across different industries, suggesting the CU has significantly improved the trade on textiles, transportation, machinery, metals and plastics/rubbers, but negligibly influence agriculture, mineral and chemicals. Furthermore, the study also evidences that the impact of the CU is stronger in EU's export to Turkey than Turkey's export to the EU. Finally, CU's...

The main purpose of this dissertation is to explore the trade potentials between Central and Eastern Europe countries and China. According to the collected information and data, this dissertation believes that although there are some shortcomings in the trade between CEE countries and China, CEE countries' trade potentials with China are relatively high. This is because, on the one hand, by observing the trend of the trade development in the past ten years, it could be found that the trade scale between CEE countries and China has been continuously increasing. Combined with the trade competitiveness and trade complementarity between CEE countries and China, this dissertation believes that the practical basis for trade cooperation between CEE countries and China is relatively strong. For example, Latvia has an obvious competitive advantage and trade complementarity in crude materials, inedible, except fuels (SITC 2). On the other hand, according to the trade potential ratios calculated by the trade gravity model, the overall trade potential ratios between CEE countries and China are not significantly high, which suggests that CEE countries and China still have strong trade potentials in export and import trade. Keywords: Central and Eastern Europe countries, China, trade potential, trade gravity...

Proper modelling of the gravitational fields of irregularly shaped asteroids and comets is an essential yet challenging part of any spacecraft visit and flyby to these bodies. Accurate density representations provide crucial information for proximity missions, which rely heavily on it to design safe and efficient trajectories. This work explores using a spacecraft swarm to maximise the measured gravitational signal in a hypothetical mission around the comet 67P/Churyumov-Gerasimenko. Spacecraft trajectories are simultaneously computed and evaluated using a high-order numerical integrator and an evolutionary optimisation method to maximise overall signal return. The propagation is based on an open-source polyhedral gravity model using a detailed mesh of 67P/C-G and considers the comet’s sidereal rotation. We compare performance on various mission scenarios using one and four spacecraft. The results show that the swarm achieved an expected increase in coverage over a single spacecraft when considering a fixed mission duration. However, optimising for a single spacecraft results in a more effective trajectory. The impact of dimensionality is further studied by introducing an iterative local search strategy, resulting in a generally improved robustness for finding efficient solutions. Overall, this work serves as a testbed for designing a set of trajectories in particularly complex gravitational environments, balancing measured signals and risks in a swarm scenario. / En korrekt modellering av de gravitationsfält som uppstår runt irreguljärt formade asteroider och kometer är en avgörande och utmanande del för alla uppdrag till likartade himlakroppar. Exakta densitetsrepresentationer tillhandahåller viktig information för att säkerställa säkra och effektiva rutter för särsilt närgående rymdfarkoster. I denna studie utforskar vi användningen av en svärm av rymdfarkoster för att maximera den uppmätta gravitationssignalen i ett hypotetisk uppdrag runt kometen 67P/Churyumov-Gerasimenko. Rymdfarkosternas banor beräknas och utvärderas i parallella scheman med hjälp av en högre ordningens numerisk integration och en evolutionär optimeringsmetod i syfte att maximera den totala uppmätta signalen. Beräkningarna baseras på en öppen källkod för en polyhedral gravitationsmodell som använder ett detaljerat rutnät av triangulära polygoner för att representera 67P/C-G och beaktar kometens egna rotation. Vi jämför sedan prestanden för olika uppdragscenarier med en respektive fyra rymdfarkoster. Resultaten visar att svärmen uppnådde en förväntad ökning i täckning jämfört med en enskild rymdfarkost under en fast uppdragsvaraktighet. Dock resulterar optimering för en enskild rymdfarkost i en mer effektiv bana. Påverkan av dimensionshöjningen hos oberoende variabler studeras vidare genom att introducera en iterativ lokal sökstrategi, vilket resulterar i en generellt förbättrad robusthet samt effektivare lösningar. Sammantaget fungerar detta arbete som en testbädd för att studera och utforma rymdfarkosters banor i särskilt komplexa gravitationsmiljöer, samt för att balansera uppmätta signaler och risker i ett svärmscenario.

<p>This dissertation consists of three major chapters. The first chapter is dedicated to testing a novel gravity model of international trade, while the last two chapters explore cross-country commitment and implementation behavior within the World Trade Organization’s Trade Facilitation Agreement. </p> <p><strong>Chapter 1:</strong> I test a novel theoretical gravity model of international trade on firm-level export data from Colombia in 2018. The model assumes a power law relationship between trade flows and distance, with the distance elasticity resulting from two dynamic processes: firm-export growth captured in a Pareto distribution; and the growth of the distance over which those exports are sold. Although the model has been shown to work well in French data, its usefulness for interpreting data from other countries remains unexplored. I find evidence that the model fails in Colombia because some large firms contradict its assumptions by exhibiting shorter export distances compared to smaller firms in the sample. I hypothesize that these large firms are branches of foreign multinational corporations (MNCs). MNCs’ headquarters constraint the export growth of its affiliates as well as the markets they reach. While I cannot prove firms’ MNC affiliation, I use export sophistication as an imperfect metric to reflect MNC presence. When MNC affiliates are excluded from the sample, firm export distance rises faster with firm size, leading to improved predictions of the distance elasticity of trade in Colombia by the model. These findings have implications not only for the tested model but also for other theories that explain gravity in international trade through firm-level behavior.</p> <p><strong>Chapter 2:</strong> We use a new database of commitments made during the process of ratifying the Trade Facilitation Agreement (TFA) to study variation in countries’ commitment behavior. The TFA is a novel World Trade Organization agreement because it allows developing countries to select commitments from a menu of best practices in trade facilitation, rather than to consent, or not, to a comprehensive package of negotiated commitments. The operation of this <em>à la carte</em> approach to concluding trade agreements is worthy of study in its own right, but the commitment data also offer a high-level description of progress in an international effort to improve border management procedures around the globe. Our study uses data on TFA commitments to describe progress across subcomponents of the agreement. A regression model shows that the number of Type A trade facilitation commitments that a country made in the TFA ratification process depends on its level of development, population size, ability to control corruption, and foreign aid received to support trade facilitation. We use multidimensional scaling techniques to study differences in the content of national commitment bundles. This approach demonstrates that variation in the content of countries’ commitments is closely tied to the number of commitments made.</p> <p><strong>Chapter 3:</strong> This chapter examines the implementation progress of the Trade Facilitation Agreement (TFA) from 2019 to 2023. The TFA, which is the latest World Trade Organization agreement, came into force in 2017. In its novelty, it allows developing countries to set their own implementation schedule and adjust it if needed. This flexibility aligns implementation requirements with the capabilities of signatory countries, but introduces uncertainties in achieving complete global implementation and fully realizing the potential benefits of the agreement. Using data on the notified implementation dates for each measure of the TFA, this study describes the progress made in implementing different subcomponents of the agreement over a period of five years. A regression analysis suggests that the annual rate of progress towards achieving full TFA implementation does not vary based on country characteristics such as GDP per capita, population size, or landlocked status. Assuming that the tendency at which countries implement measures remains unchanged, I project that 95% of developing countries will achieve 95% TFA implementation between the years 2036 and 2047.</p>

This study examines the fundamental determinants of bilateral trade flows between South Africa and BRIC countries. This is done by exploring the magnitude of exports among these countries. The Gravity model approach is used as the preferred theoretical framework in explaining and evaluating successfully the bilateral trade flows between South Africa and BRIC countries The empirical part of this study uses panel data methodology covering the time period 2000-2012 and incorporates the five BRICS economies in the sample. The results of the regressions are subject to panel diagnostic test procedures. The study reveals that, on the one hand, there are positive and significant relationships between South African export flows with the BRICs and distance, language dummy, the BRICs’ GDP, the BRICs’ openness and population in South Africa. On the other hand, GDP in South Africa, real exchange rate and time dummy are found to be negatively related to export flows. / Economics / M. Com. (Economics)

多邊主義下帶動之「全球化」及區域主義下所帶動之「區域化」皆已成為現階段國際經貿發展的兩股重要潮流，透過洽簽自由貿易協定所達到之區域經濟整合，在區域內可消除絕大部份之關稅及非關稅貿易障礙，預計將有助於增進會員國間之貿易量，形成貿易創造效果，而或對於非會員國造成貿易轉向效果。故其將影響國際貿易的流向，國際資源的重分配，進而改變國際分工型態。 為瞭解區域經濟整合對於貿易流量的影響，本文首先將就區域經濟整合之定義與法源、區域經濟整合發展與現況、及台灣與各主要區域經濟整合之貿易概況進行概述。鑒於引力模型可有效的分析雙邊的貿易流量，本文針對該模型之相關文獻及實證歸納與整理，並利用引力模型，選擇全球六個重要區域經濟組織包括北美自由貿易區、歐盟、東協自由貿易區、南方共同市場、安地略集團及紐澳緊密關係協定等區域共計37個國家，以設定虛擬變數之方式實證1990年至2003年長達13年間各區域經濟整合的過程中，其對於區內會員國及對非屬會員國進、出口貿易流量之影響，特別是整合過程中對台灣是否產生貿易轉向之現象進行實證研究，並分析影響貿易流量之因素。 本實證研究發現影響二國間貿易流量的因素分別為出、進口國之國民生產毛額及人均國民生產毛額，以及距離。區域經濟整合具有明顯的貿易創造效果，而貿易轉向效果則隨經濟整合的緊密程度、區域內產業分工型態及與區域外國家出、進口結構及產業間相互競合程度不一而產生不同的影響。在上述六個區域經濟整合中，北美自由貿易區及南方共同市場對台灣產生貿易轉向的現象。本研究亦針對上述之結果與區域經濟整合實際進展現況進行交互分析。最後，本研究將就政策面及後續研究的方向提出建議，俾供參考。 / Globalization and regionalization have been the two main trends in international economic development in recent years. Already, many countries have signed Free Trade Agreements to achieve the goal of regional economic integration. This integration allows members of the region to virtually eliminate all tariff and non-tariff trade barriers and, as a result, increase trade volume between member countries. This phenomenon is called trade creation. On the other hand, trade volume between members of the region and non-member may decrease, a phenomenon called trade diversion. All of this will affect international trade flows, the allocation of international resources and change the pattern of the international industrial division. In order to learn how regional economic integration influences trade flows, this paper deals first with the definition and regulation under the GATT of regional trade agreements, the present situation and the development of regional economic integration. We also examine the current state of import and export trade between Taiwan and the main regional economies in the world. This paper reviews the relevant literature on the gravity model, a model that can effectively analyze trade flows between two countries, then proceeds to use this model with NAFTA, EU, AFTA, MERCOSUR, ANDEAN Community, and CER (Closer Economic Relationship between the Australia and New Zealand) as regional dummies. This allows us to test alterations in trade flows between members and other members as well as between members and non-members (especially Taiwan) in these six regional trade blocs for the 13 years between 1990 and 2003. This model also analyzes the main factors affecting trade flows. We find first that the main factors influencing trade flows between two countries are the GDP and per capita GDP of the importer and exporter as well as distance. Secondly, while regional economic integration clearly brings with it trade creation, the degree of trade diversion is affected by such factors as the degree of regional economic integration, the pattern of industrial division in the region, the structure of imports from and exports to non-member countries and the level of competition and cooperation in various sectors. The empirical evidence shows that NAFTA and Mercosur have resulted in trade diversion away from Taiwan. Based on our findings, we offer policy suggestions and suggestions for further research.