Alberto Costa

Alberto Costa
ETH Zurich - Future Resilient Systems, Singapore

PhD

About

43
Publications
22,782
Reads
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526
Citations
Additional affiliations
October 2017 - present
ETH Zurich
Position
  • Project Manager
Description
  • Project Coordinator for the Cyber Civil Infrastructure group
May 2015 - September 2017
National University of Singapore
Position
  • Researcher
Description
  • robust optimization
January 2013 - January 2015
Singapore University of Technology and Design
Position
  • Researcher
Description
  • black-box optimization

Publications

Publications (43)
Article
The aim of model-based structural identification is to identify suitable models and values for model parameters that determine structure behavior through comparing measurements with predictions. Well-known methodologies, such as traditional implementations of Bayesian model updating, have been shown to be inaccurate in cases characterized by system...
Article
Full-text available
The retrieval function is one of the most important components of an Information Retrieval (IR) system, because it determines to what extent some information is relevant to a user query. Most retrieval functions have “free parameters” whose value must be set before retrieval, significantly affecting the effectiveness of an IR system. Choosing the o...
Article
Full-text available
Cluster analysis refers to finding subsets of vertices of a graph (called clusters) which are more likely to be joined pairwise than vertices in different clusters. In the last years this topic has been studied by many researchers, and several methods have been proposed. One of the most popular is to maximize the modularity, which represents the fr...
Article
Full-text available
Modularity density maximization is a clustering method that improves some issues of the commonly used modularity maximization approach. Recently, some Mixed-Integer Linear Programming (MILP) reformulations have been proposed in the literature for the modularity density maximization problem, but they require as input the solution of a set of auxilia...
Article
Full-text available
Excavation is a complex multistage problem, where field responses of soil properties such as deflections at one stage of the operation depend on responses at the preceding stage. In order to help asset managers make better decisions and thus improve safety, soil properties should be accurately identified using sensor-data collected at the current s...
Article
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In this paper, we develop a distributionally robust optimization model for the design of rail transit tactical planning strategies and disruption tolerance enhancement under downtime uncertainty. First, a novel performance function evaluating the rail transit disruption tolerance is proposed. Specifically, the performance function maximizes the wor...
Article
The Internet of Things creates opportunities to develop data-driven design methodologies for smart cities. However, effects rather than causes are often measured in complex urban systems, requiring robust data-interpretation methodologies. Additionally, effective monitoring of large urban components, such as civil infrastructure, often involves mul...
Article
Full-text available
This article investigates the intersection and convergence of Smart Cities and Creative Cities that emerge with the availability of social media data, technology—smart technologies—and the shifting mode of cultural production—creative economies—forming a new nexus of Smart-Cultural Cities. It starts with a short review of literature surrounding Sma...
Article
In responsive cities, user feedback and information provided by sensors are combined to improve urban design and to support asset managers in performing decision making. Optimal management of infrastructure networks requires accurate knowledge of current asset conditions, in order to avoid unnecessary replacement and expensive interventions when ch...
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We consider the problem of optimizing an unknown function given as an oracle over a mixed-integer box-constrained set. We assume that the oracle is expensive to evaluate, so that estimating partial derivatives by finite differences is impractical. In the literature, this is typically called a black-box optimization problem with costly evaluation. T...
Article
This paper studies the problem of allocating fortification resources in an electric power grid with the aim of maximizing its immunity against malicious attacks. An attacker of the grid allocates his attack resource budget to destroy targeted transmission lines in the network. The attacker is successful if the power load shed after attack exceeds a...
Article
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In this paper we consider the optimal meeting scheduling problem in a commercial building over a fixed period of time, with the objectives of minimizing the cost of energy consumption by the air-conditioning system and possibly achieving more balanced power distribution. By considering a set of realistic factors, including the eligible time slots o...
Article
In this paper we consider a particular method of clustering for graphs, namely the modularity density maximization. We propose a hierarchical divisive heuristic which works by splitting recursively a cluster into two new clusters by maximizing the modularity density, and we derive four reformulations for the mathematical programming model used to o...
Article
Full-text available
Climate change, resource depletion, and worldwide urbanization feed the demand for more energy and resource-efficient buildings. Increasingly, architectural designers and consultants analyze building designs with easy-to-use simulation tools. To identify design alternatives with good performance, designers often turn to optimization methods. Random...
Article
Full-text available
Information retrieval (IR) systems are designed, in general, to satisfy the information need of a user who expresses it by means of a query, by providing him with a subset of documents selected from a collection and ordered by decreasing relevance to the query. Such systems are based on IR models, which define how to represent the documents and the...
Article
Full-text available
We develop a mathematical programming approach to schedule meetings in an organization over a fixed period of time, while minimizing the wasted energy and possibly achieving more balanced demand distribution. The problem is formulated as a mixed integer linear program subject to a set of realistic constraints including people's available time slots...
Conference Paper
Full-text available
This paper deals with an application of optimization in architectural design. Formally, we consider the problem of optimizing a function that can only be evaluated through an expensive oracle. We assume that the analytical expression of the function is unknown and first-order information is not available. This situation frequently occurs when each...
Conference Paper
We develop a mathematical programming approach to schedule meetings in an organization over a fixed period of time, while minimizing the wasted energy and possibly achieving more balanced demand distribution. The problem is formulated as a mixed integer linear program subject to a set of realistic constraints including people's available time slots...
Article
Finding clusters, or communities, in a graph, or network is a very important problem which arises in many domains. Several models were proposed for its solution. One of the most studied and exploited is the maximization of the so called modularity, which represents the sum over all communities of the fraction of edges within these communities minus...
Article
Full-text available
A quantitative function for community detection called modularity density has been proposed by Li, Zhang, Wang, Zhang, and Chen in $[$Phys. Rev. E 77, 036109 (2008)$]$. Among the properties presented by the authors, some of them are not proved or need to be clarified, e.g., the NP-hardness of the problem, the fact that the modularity density of eac...
Article
Given a set of entities, cluster analysis aims at finding subsets, also called clusters or communities or modules, entities of which are homogeneous and well separated. In the last ten years clustering on networks, or graphs, has been a subject of intense study. Edges between pairs of vertices within the same cluster should be relatively dense, whi...
Article
Full-text available
Finding communities in complex networks is a topic of much current research and has applications in many domains. On the one hand, criteria for doing so have been proposed, the most studied of which is modularity. On the other hand, properties to be satisfied by each community have been suggested. It has recently been observed that one of the best...
Article
We consider the problem of placing n points in the unit square in such a way as to maximize their minimum pairwise distance m. Starting from two properties of the optimal solution presented by Locatelli and Raber in [Discrete Applied Mathematics 122 (1-3) (2002) 139-166], and using the known theoretical lower and upper bounds, we derive some constr...
Article
We study the problem of packing equal circles in a square from the mathematical programming point of view. We discuss different formulations, we analyze formulation symmetries, we propose some symmetry breaking constraints and show that not only do they tighten the convex relaxation bound, but they also ease the task of local NLP solution algorithm...
Article
Full-text available
Mathematical programming is a technique that can be used to solve real-world optimization problems, where one wants to maximize, or minimize, an objective function subject to some constraints on the decision variables. The key features of mathematical programming are the creation of a model for describing the problem (the so called formulation), an...
Conference Paper
Bilinear, trilinear, quadrilinear and general multilinear terms arise naturally in several important applications and yield nonconvex mathematical programs, which are customarily solved using the spatial Branch-and-Bound algorithm. This requires a convex relaxation of the original problem, obtained by replacing each multilinear term by appropriatel...
Article
Full-text available
Finding communities, or clusters or modules, in networks can be done by optimizing an objective function defined globally and/or by specifying conditions which must be satisfied by all communities. Radicchi et al. [Proc. Natl. Acad. Sci. USA 101, 2658 (2004)] define a susbset of vertices of a network to be a community in the strong sense if each ve...
Article
The Packing Equal Circles in a Square (PECS) problem is a nonconvex nonlinear optimization problem which involves a high degree of symmetry. The Branch-and-Bound algorithms work bad due to the presence of symmetric optima, because the Branch-and-Bound tree becomes large, and the time to reach the leaves (i.e., the optimal solutions) increases. In t...
Article
Full-text available
In a recent paper, Zhan, Zhang, Guan, and Zhou [Phys. Rev. E 83, 066120 (2011)] presented a modified adaptive genetic algorithm (MAGA) tailored to the discovery of maximum modularity partitions of the node set into communities in unipartite, bipartite, and directed networks. The authors claim that "detection of communities in unipartite networks or...
Conference Paper
Full-text available
In the Recommender Systems field ensemble techniques gain growing interest. This approach is based on the idea of mixing many recommenders and to get an average prediction from all of them. Even if it is useful this process may be very expensive from a computational point of view. We propose the use of Operations Research techniques in order to opt...
Article
Full-text available
In this paper, we describe the solution for a problem dealing with definite properties of binary sequences. This problem, proposed by Xavier Grandsart in the form of a mathematical contest, has been solved also by Maher Younan, Ph.D. student of Theoretical Physics at the University of Geneva, and Pierre Deligne, professor at Princeton and Field Med...
Article
Full-text available
In this paper we present a method for reformulating the Recommender Systems problem in an Information Retrieval one. In our tests we have a dataset of users who give ratings for some movies; we hide some values from the dataset, and we try to predict them again using its remaining portion (the so-called "leave-n-out approach"). In order to use an I...
Article
The performance of Branch-and-Bound algorithms is severely impaired by the presence of symmetric optima in a given problem. We describe a method for the automatic detection of formulation symmetries in MINLP instances. A software implementation of this method is used to conjecture the group structure of the problem symmetries of packing equal circl...
Conference Paper
Full-text available
Information Retrieval (IR) systems combine a variety of techniques stemming from logical, vector-space and probabilistic models. This variety of combinations has produced a significant increase in retrieval effectiveness since early 1990s. Nevertheless, the quest for new frameworks has not been less intense than the research in the optimization and...

Questions

Question (1)
Question
Hi all,
I am looking for datasets (small-medium size) representing computer networks. For example, nodes can be PC, servers, routers and an arc between two nodes indicates a physical (or virtual) connection. It would be great to have also informations as capacity of the nodes/arcs (for example bandwidth/throughput for lines and routers). Is there any public collection of such datasets?
Thank you!

Projects

Projects (2)
Project
This project aims to develop and apply techniques for population-based back analysis of geotechnical excavations.
Project
Smart-Cultural Cities