Statistical disclosure control in tabular data

Data disseminated by National Statistical Agencies (NSAs) can be classified as either microdata or tabular data. Tabular data is obtained from microdata by crossing one or more categorical variables. Although cell tables provide aggregated information, they also need to be protected. This chapter is a short introduction to tabular data protection. It contains three main sections. The first one shows the different types of tables that can be obtained, and how they are modeled. The second describes the practical rules for detection of sensitive cells that are used by NSAs. Finally, an overview of protection methods is provided, with a particular focus on two of them: “cell suppression problem” and “controlled tabular adjustment”.Postprint (published version

Thirty years of optimization-based SDC methods for tabular data

In 1966 Bacharach published in Management Science a work on matrix rounding problems in two-way tables of economic statistics, formulated as a network optimization problem. This is likely the first application of optimization/operations research for statistical disclosure control (SDC) in tabular data. Years later, in 1982, Cox and Ernst used the same approach in a work in INFOR for a similar problem: controlled rounding. And thirty years ago, in 1992, a paper by Kelly, Golden and Assad appeared in Networks about the solution of the cell suppression problem, also using network optimization. Cell suppression was used for years as the main SDC technique for tabular data, and it was an active field of research which resulted in several lines of work and many publications. The above are some of the seminal works on the use of optimization methods for SDC when releasing tabular data. This paper discusses some of the research done this field since then, with a focus on the approaches that were of practical use. It also discusses their pros and cons compared to recent techniques that are not based on optimization methods.Peer ReviewedPostprint (published version

Cell suppression problem: A genetic-based approach

Cell suppression is one of the most frequently used techniques to prevent the disclosure of sensitive data in statistical tables. Finding the minimum cost set of nonsensitive entries to suppress, along with the sensitive ones, in order to make a table safe for publication, is a NP-hard problem, denoted the cell suppression problem (CSP). In this paper, we present GenSup, a new heuristic for the CSP, which combines the general features of genetic algorithms with safety conditions derived by several authors. The safety conditions are used to develop fast procedures to generate multiple initial solutions and also to recombine, to perturb and to repair solutions in order to improve their quality. The results obtained for 300 tables, with up to more than 90,000 entries, show that GenSup is very effective at finding low-cost sets of complementary suppressions to protect confidential data in two-dimensional tables.(2008).info:eu-repo/semantics/publishedVersio

Capacity modeling for admission control in WiMAX networks

WiMAX networks support QoS reservation of resources by allowing a new flow to apply for admittance in the system. Thus, there is a need for an accurate estimation of the available capacity to be shared by incoming connections. Admission control algorithm must ensure that, when a new QoS resource reservation is accepted, reservations already present in the system continue having their QoS guarantees honored. Its efficiency is then expressed in terms of accuracy and computational complexity which is the focus of the work in this thesis. Different approaches are presented to compute the aggregated allocated capacity in WiMAX networks and, based on their limitations, the E-Diophantine solution has been proposed. The mathematical foundations for the designed approach are provided along with the performance improvements to be expected, both in accuracy and computational terms, as compared to three alternatives of increasing complexity. The different solutions considered are validated and evaluated with OPNET’s WiMAX simulator in a realistic scenario. Finally, the multi-hop relay case is analyzed: a capacity model description is provided together with a conjectured reuse of the admission control algorithm designed

ECLSS advanced automation preliminary requirements

A description of the total Environmental Control and Life Support System (ECLSS) is presented. The description of the hardware is given in a top down format, the lowest level of which is a functional description of each candidate implementation. For each candidate implementation, both its advantages and disadvantages are presented. From this knowledge, it was suggested where expert systems could be used in the diagnosis and control of specific portions of the ECLSS. A process to determine if expert systems are applicable and how to select the expert system is also presented. The consideration of possible problems or inconsistencies in the knowledge or workings in the subsystems is described

Reliability Assessment and Optimization of Water Distribution Systems Explicitly Considering Isolation Valve Locations

Water distribution systems have changed the landscape of communities through two services: 1) providing water supply for domestic and industrial use, and 2) providing water required to fight fires. However, a substantial portion of the water infrastructure in the country, as many of other public assets built over 50 years ago, are now reaching the end of their useful life; which combined with rapid growth and changes in demographics have placed water distribution pipe networks at a state that requires revitalization. The aging infrastructure along with the growing threat of natural and man-made disruptions have led water utilities to place a greater emphasis on developing better strategies to minimize the impact on the system users when a failure event occurs (i.e., improve the reliability of the system). The proposed segment-based analysis considers valve location to estimate the number of pipes taken out of service to seclude the initial pipe break or element failure. The objective of the assessment is to identify critical segments (i.e., smallest set of pipes that can be secluded using the closest isolation valves) and critical valves in a set of real water distribution networks. The critical elements, the segments or valves that when taken out of service cause the greatest reduction in the supply delivered and the level of service provided, are identified using the performance metrics based on: loss of connectivity, and the failure to meet hydraulic and fire protection requirements. This type of assessment seeks to be a simple method to provide information on critical elements that considers the role of isolation valves, thus offering a more realistic view of the effects of a breakdown. This framework is then used to define valve locations that could offer the improvement in reliability for a given capital investment

Occlusion reasoning for multiple object visual tracking

Thesis (Ph.D.)--Boston UniversityOcclusion reasoning for visual object tracking in uncontrolled environments is a challenging problem. It becomes significantly more difficult when dense groups of indistinguishable objects are present in the scene that cause frequent inter-object interactions and occlusions. We present several practical solutions that tackle the inter-object occlusions for video surveillance applications. In particular, this thesis proposes three methods. First, we propose "reconstruction-tracking," an online multi-camera spatial-temporal data association method for tracking large groups of objects imaged with low resolution. As a variant of the well-known Multiple-Hypothesis-Tracker, our approach localizes the positions of objects in 3D space with possibly occluded observations from multiple camera views and performs temporal data association in 3D. Second, we develop "track linking," a class of offline batch processing algorithms for long-term occlusions, where the decision has to be made based on the observations from the entire tracking sequence. We construct a graph representation to characterize occlusion events and propose an efficient graph-based/combinatorial algorithm to resolve occlusions. Third, we propose a novel Bayesian framework where detection and data association are combined into a single module and solved jointly. Almost all traditional tracking systems address the detection and data association tasks separately in sequential order. Such a design implies that the output of the detector has to be reliable in order to make the data association work. Our framework takes advantage of the often complementary nature of the two subproblems, which not only avoids the error propagation issue from which traditional "detection-tracking approaches" suffer but also eschews common heuristics such as "nonmaximum suppression" of hypotheses by modeling the likelihood of the entire image. The thesis describes a substantial number of experiments, involving challenging, notably distinct simulated and real data, including infrared and visible-light data sets recorded ourselves or taken from data sets publicly available. In these videos, the number of objects ranges from a dozen to a hundred per frame in both monocular and multiple views. The experiments demonstrate that our approaches achieve results comparable to those of state-of-the-art approaches

DC & Hybrid Micro-Grids

This book is a printed version of the papers published in the Special Issue “DC & Hybrid Microgrids” of Applied Sciences. This Special Issue, co-organized by the University of Pisa, Italy and Østfold University College in Norway, has collected nine papers and the editorial, from 28 submitted, with authors from Asia, North America and Europe. The published articles provide an overview of the most recent research advances in direct current (DC) and hybrid microgrids, exploiting the opportunities offered by the use of renewable energy sources, battery energy storage systems, power converters, innovative control and energy management strategies