Anonymizing Social Graphs via Uncertainty Semantics

Rather than anonymizing social graphs by generalizing them to super nodes/edges or adding/removing nodes and edges to satisfy given privacy parameters, recent methods exploit the semantics of uncertain graphs to achieve privacy protection of participating entities and their relationship. These techniques anonymize a deterministic graph by converting it into an uncertain form. In this paper, we propose a generalized obfuscation model based on uncertain adjacency matrices that keep expected node degrees equal to those in the unanonymized graph. We analyze two recently proposed schemes and show their fitting into the model. We also point out disadvantages in each method and present several elegant techniques to fill the gap between them. Finally, to support fair comparisons, we develop a new tradeoff quantifying framework by leveraging the concept of incorrectness in location privacy research. Experiments on large social graphs demonstrate the effectiveness of our schemes

Detecting Communities under Differential Privacy

Complex networks usually expose community structure with groups of nodes sharing many links with the other nodes in the same group and relatively few with the nodes of the rest. This feature captures valuable information about the organization and even the evolution of the network. Over the last decade, a great number of algorithms for community detection have been proposed to deal with the increasingly complex networks. However, the problem of doing this in a private manner is rarely considered. In this paper, we solve this problem under differential privacy, a prominent privacy concept for releasing private data. We analyze the major challenges behind the problem and propose several schemes to tackle them from two perspectives: input perturbation and algorithm perturbation. We choose Louvain method as the back-end community detection for input perturbation schemes and propose the method LouvainDP which runs Louvain algorithm on a noisy super-graph. For algorithm perturbation, we design ModDivisive using exponential mechanism with the modularity as the score. We have thoroughly evaluated our techniques on real graphs of different sizes and verified their outperformance over the state-of-the-art

Programmes optimaux d’investissement en R & D

This article presents a model of inventive activity and capital accumulation. It also suggests ways of estimating optimal investment in research and development and outlines in the same time some econometric problems associated to measurement. In such a model, it has been shown that increases in technical knowledge are fundamentally related to the amount of resources devoted to inventive activity. Thus the role of invention in economic growth is explicitly recognize

La stabilité de l’OPEP

In the energy field and more specifically in the petroleum sector, several models have been developed with a view to determining long-term price strategies and supply and demand flows without considering the sector in question from an oligopolistic perspective : institutions have been excluded from these models. This study explicitly recognizes the importance of variables often characterized as extra-economic and proposes to examine the degree of OPEC's stability. Among the factors that could negatively influence this stability are bilateral oil agreements, the coalition of consumer countries within the International Energy Agency and rivalry among the members of OPEC. The respective weight of each of these factors has been carefully examined.On the other hand, an oil price indexing formula accepted and respected by all parties concerned would ensure the stability of this organization. However, stability via indexing is unlikely as it is difficult to find a formula acceptable to all parties. It is therefore to be anticipated that the world energy and petroleum situation in the near future will be a function of the policies of the two poles : the United States, the largest consumer, and Saudi Arabia, the largest producer. The functions-objectives of these two countries have also been examined in order to derive a number of specific hypotheses relative to the eventual evolution of the energy and petroleum sector

浅い感潮水路における塩分と潮流の空間的および時間的変動性

広島大学(Hiroshima University)博士(工学)Doctor of Engineeringdoctora

The Cenozoic evolution of the South Vietnam margin of the South China Sea and the origin of coastal placer deposits

Vietnam mineral reserves contribute significantly to its economy and South Vietnam is especially rich in these resources. Whilst this region is well known as a source of oil and gas, extracted from offshore basins it is also an exporter of titanium ore extracted from coastal sands rich in heavy minerals. Despite decades of exploitation there remain fundamental questions about the origins of these resources that form the aims of this thesis. Specifically, 1) Where did the titanium bearing mineral known as ilmenite found in the heavy mineral sands come from? 2) How is the sedimentation history of the hydrocarbon basins connected to the uplift and erosion history of South Vietnam? To answer these questions an extensive set of rock and sand samples were collected from across the region and analysed using a combination of detrital zircon geochronology, petrology, geochemistry and apatite thermochronometry. In answer to question one results showed that the placer sands along coastal southern Vietnam came from local river catchments rich in outcrops of Cretaceous granites. The geochemical and petrological data also showed ilmenite titanium contents increased to the south, explained by a wider continental shelf that increased exposure to weathering during glacial sea-level lowstands before rising sea- levels remobilised the sand. Question two was answered by apatite thermochronometry data that detected increased rock uplift between 25-15 Ma across most of South Vietnam. This timing is significant as local marine basins also show inversion and a regional unconformity at the Oligocene/Miocene boundary. Following inversion basins subsided under the load of thick sands produced by erosion of the onshore region. These data provide the first solid link between basin sedimentation and onshore erosion. The cause of uplift is likely related to a change in regional stress field linked to ocean spreading in the South China Sea

Superiority of Exporters and the Causality Between Exporting and Firm Characteristics in Vietnam

The study in this paper is on the causal relationship between export activities of firms and their characteristics in a transition country that is pursuing export-led growth strategies and experiencing a fast track of trade liberalization. For this purpose, we examine the superiority of exporters using a panel of firm-level data of manufacturing firms in Vietnam. We observe that exceptional performance of exporters, especially in TFP, does prevail in this country. Via testing self-selection hypothesis using a random-effects dynamic probit model to examine the causality from firm characteristics to export probability, we find significantly positive impacts of factors such as firm size, age or foreign ownership but not that of TFP. However, TFP superiority of exporters is satisfactorily explained by the existence of learning-by-exporting effects that are tested in a multivariate analysis using matching technique in combination with difference-in-differences approach. Besides contributing an empirical analysis to heterogeneous-firm trade theories, this study gives us some insights into the interpretation of mixed findings in macro-analysis of the effects of exports on growth in Vietnam.Exporter superiority, Self-selection, Learning-by-exporting, Vietnam