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See detailAn Optimal Sensor Placement Algorithm taking into account Diagnosability Specifications
Yassine, Abed Alrahim; Rosich, Albert UL; Ploix, Stéphane

in Automation Quality and Testing Robotics (AQTR), 2010 IEEE International Conference on (Volume:2 (2010)

Suitable installed sensors in a industrial process is a necessary condition for fault diagnosis. Sensor placement for diagnosis purposes is to study which process variables have to be measured to satisfy ... [more ▼]

Suitable installed sensors in a industrial process is a necessary condition for fault diagnosis. Sensor placement for diagnosis purposes is to study which process variables have to be measured to satisfy diagnosis specifications (detectability, dis-criminability and diagnosability). This paper presents a method based on the study of the structural model properties and the Dulmage-Mendelsohn decomposition. Due to the use of structural models, the proposed approach can be applied to a wide variety of system (linear, algebraic, dynamics, etc.). Assuming that the cost of placing a sensor for each possible variable is defined, this method finds the minimal cost sensor configuration according to the diagnosability criteria. This method does not require the computation of testable subsystems [less ▲]

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See detailOptimal Sensor Placement for FDI using Binary Integer Linear Programming
Rosich, Albert UL; Sarrate, Ramon; Nejjari, Fatiha

in 20th International Workshop on Principles of Diagnosis (2009)

This work is devoted to find an optimal set of sensors for model-based FDI. The novelty is that linary integer linear programming is used in the optimization problem, leading to a formulation of the ... [more ▼]

This work is devoted to find an optimal set of sensors for model-based FDI. The novelty is that linary integer linear programming is used in the optimization problem, leading to a formulation of the detectability and isolability specifications as linear inequality constraints. Furthermore, a very detailed system model is not needed since the methodology handles structural models. The approach has been successfully applied to a two-tank system, as an illustrative example. [less ▲]

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See detailOptimal Sensor Placement For Fuel Cell System Diagnosis using BILP Formulation
Nejjari, Fatiha; Sarrate, Ramon; Rosich, Albert UL

in Control & Automation (MED), 2010 18th Mediterranean Conference on (2010)

This paper presents the application of a new methodology for Fault Detection and Isolation (FDI) to a Fuel Cell System. The work is devoted to find an optimal set of sensors for model-based FDI. The ... [more ▼]

This paper presents the application of a new methodology for Fault Detection and Isolation (FDI) to a Fuel Cell System. The work is devoted to find an optimal set of sensors for model-based FDI. The novelty is that binary integer linear programming (BILP) is used in the optimization formulation, leading to a reformulation of the detectability and isolability specifications as linear inequality constraints. The approach has been successfully applied to a Fuel Cell System. [less ▲]

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See detailOptimal Sensor Placement for Leak Location in Water Distribution Networks Using Genetic Algorithms
Casillas, Myrna V.; Puig, Vicenç; Garza-Castañon, Luis E. et al

in 2nd International Conference on Control and Fault-Tolerant Systems (2013)

In this paper, a new approach for sensor placement in water distribution networks (WDN) is proposed. The sensor placement problem is formulated as an integer optimization problem. The optimization ... [more ▼]

In this paper, a new approach for sensor placement in water distribution networks (WDN) is proposed. The sensor placement problem is formulated as an integer optimization problem. The optimization criterion consists in minimizing the number of non-isolable leaks according to the isolability criteria introduced. Because of the non-linear integer and large-scale nature of the resulting optimization problem, genetic algorithms (GA) are used as solution approach. To validate the results obtained, they are compared with exhaustive search methods with higher computational cost proving that GA allow to find near-optimal solutions with less computational load. The proposed sensor placement algorithm is combined with a projection-based isolation scheme. However, the proposed methodology does not depend on the isolation method chosen by the user and it could be easily adapted to any other isolation scheme. Experiments on a real network allow to evaluate the performance of such approach. [less ▲]

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See detailOptimal Sensor Placement for Leak Location in Water Distribution Networks Using Genetic Algorithms
Casillas, Myrna V.; Puig, Vicenç; Garza-Castañon, Luis E. et al

in Sensors (2013), 13(11), 14984-15005

This paper proposes a new sensor placement approach for leak location in water distribution networks (WDNs). The sensor placement problem is formulated as an integer optimization problem. The optimization ... [more ▼]

This paper proposes a new sensor placement approach for leak location in water distribution networks (WDNs). The sensor placement problem is formulated as an integer optimization problem. The optimization criterion consists in minimizing the number of non-isolable leaks according to the isolability criteria introduced. Because of the large size and non-linear integer nature of the resulting optimization problem, genetic algorithms (GAs) are used as the solution approach. The obtained results are compared with a semi-exhaustive search method with higher computational effort, proving that GA allows one to find near-optimal solutions with less computational load. Moreover, three ways of increasing the robustness of the GA-based sensor placement method have been proposed using a time horizon analysis, a distance-based scoring and considering different leaks sizes. A great advantage of the proposed methodology is that it does not depend on the isolation method chosen by the user, as long as it is based on leak sensitivity analysis. Experiments in two networks allow us to evaluate the performance of the proposed approach. [less ▲]

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See detailOptimal Sensor Placement for Leakage Detection and Isolation in Water Distribution Networks
Rosich, Albert UL; Sarrate, Ramon; Nejjari, Fatiha

in Fault Detection, Supervision and Safety of Technical Processes, Volume# 8 | Part# 1 (2012)

In this paper, the problem of leakage detection and isolation in water distribution networks is addressed applying an optimal sensor placement methodology. The chosen technique is based on structural ... [more ▼]

In this paper, the problem of leakage detection and isolation in water distribution networks is addressed applying an optimal sensor placement methodology. The chosen technique is based on structural models and thus it is suitable to handle non-linear and large scale systems. A drawback of this technique arises when costs are assigned uniformly. A main contribution of this paper is the proposal of an iterative methodology that focuses on identifying essential sensors which ultimately leads to an improvement of the optimal search efficiency. The algorithm presented in this work is successfully applied to a District Metered Area (DMA) in the Barcelona water distribution network. [less ▲]

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See detailOptimal Sensor Placement for Model-Based Fault Detection and Isolation
Sarrate, Ramon; Puig, Vicenç; Escobet, Teresa et al

in Decision and Control, 2007 46th IEEE Conference on (2007)

The problem of optimal sensor placement for FDI consists in determining the set of sensors that minimizes a pre-defined cost function satisfying at the same time a pre- established set of FDI ... [more ▼]

The problem of optimal sensor placement for FDI consists in determining the set of sensors that minimizes a pre-defined cost function satisfying at the same time a pre- established set of FDI specifications for a given set of faults. The main contribution of this paper is to propose an algorithm for model-based FDI sensor placement based on formulating a mixed integer optimization problem. FDI specifications are translated into constraints of the optimization problem considering that the whole set of ARRs has been generated, under the assumption that all candidate sensors are installed. To show the effectiveness of this approach, an application based on a two-tanks system is proposed. [less ▲]

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See detailThe optimal size of a permit market
Krysiak, Frank C.; Schweitzer, Patrick UL

in Journal of Environmental Economics and Management (2010), 60(2), 133-143

Regulating the emissions of non-uniformly mixed pollutants with a permit market carries the risk of hot spot formation, which can be reduced by dividing the regulation area into trading zones. The trading ... [more ▼]

Regulating the emissions of non-uniformly mixed pollutants with a permit market carries the risk of hot spot formation, which can be reduced by dividing the regulation area into trading zones. The trading zone approach has been extensively discussed for the full-information case. We consider incomplete information concerning the emitters’ abatement costs, their locations, and pollution dispersion. We derive the optimal number of trading zones and the optimal number of permits per zone and analyze under which conditions a system of independent trading zones is superior to other policy measures. Our results show that appropriately sized permit markets are well-suited to regulating non-uniformly mixed pollutants under informational constraints if firms are not too heterogeneous. Only for substantial heterogeneity and a highly non-linear damage function can it be optimal to use command-and-control strategies. [less ▲]

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See detailOptimal station localization for bicycle sharing system
Medard de Chardon, Cyrille UL

Scientific Conference (2013, September 07)

Many urban planning strategies for sustainable cities (New Urbanism, Mixed Use Development and Compact City) tout the need for smaller more compact communities [1, 2, 3]. These urban forms depend on a ... [more ▼]

Many urban planning strategies for sustainable cities (New Urbanism, Mixed Use Development and Compact City) tout the need for smaller more compact communities [1, 2, 3]. These urban forms depend on a modal shift from automobiles to walking and cycling. As this shift is unlikely to be driven by the markets, increases in sustainable modal transport, infrastructure and disincentives for driving [4] are necessary [5]. In some cities, bicycle sharing systems (BSS) have been catalysts for increasing cycling through their ability to extend existing public transit systems, encourage cycling accessibility and visibility. Cycling has many direct and indirect health benefits such as cardiovascular and reduced CO emissions, compared to car transport, respectively as well as social and equity benefits [6, 5:123]. BSSs are composed of bicycles and spatially fixed stations containing a constant number of docks. Two important advantages of the current generation BSSs are simplicity and security [7]; bicycle theft is difficult yet subscribers may checkout bicycles quickly and without difficulty, allowing users to seamlessly transfer between transport modes. The central question of this research is determining whether a mismatch occurs between BSS’s stations’ optimal locations based on origin and destination demands of potential cyclists and the existing stations. Most BSSs are being managed by private corporations, which often use advertising to subsidize the systems. BSS stations, or kiosks, often have double purposes of providing BSS services, such as checking out a bike, and displaying advertising. Effectively locating BSS stations throughout an urban fabric is of crucial importance to the adoption of the BSS. The optimal locations for advertising billboards and BSS stations are unlikely to consistently correspond. This conflict of interest has been explicitly anticipated by at least one city developing a BSS [8]. The overlap between optimal advertiser locations and stations for BSSs are destinations of high traffic such as commercial and transportation hubs. Conversely, BSS stations may insufficiently serve residential areas far from or without through-roads due to having decreased traffic and therefore marketing potential. This project addresses the question in three steps. The first is the gathering of spatial and spatio-temporal data related to cycling demand in order to develop demand surfaces. Next, demand is contrasted against existing BSS station infrastructure. Assessment is complex due to the alternate realities between data, theory and the practical operations of placing stations within available space constraints and the varying BSS priorities, such as social or racial equity, of cities. Finally we develop a model that optimally locates BSS stations for public use across the urban fabric based on demand and network distances between stations. Performing this process across multiple cities with BSSs we bring insight into whether a localization bias exists towards high throughput and advertising valued locations. Bicycle sharing systems may become the first new ubiquitous ‘public’ transport system in over a century. However, the initial privatization of this new transport system, whose impacts and evolution are not yet completely understood, may result in inefficiencies with lasting negative outcomes. The inadequate development of a city’s BSS may cause it to fail and stigmatize a progressive sustainable transport alternative for a generation. [less ▲]

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See detailOptimal strategy for multiple-phase estimation under practical measurement with multimode NOON states
Ur Rehman, Junaid UL; Hong, Seongjin; Lee, Seung-Woo et al

in Physical Review. A. (2022), 106

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See detailOptimal Switching from Competition to Cooperation: A Preliminary Exploration
Boucekkine, Raouf; Camacho, Carmen; Zou, Benteng UL

in Haunschmied, Josef; Kovacevic, Raimund; Semmler, Willi (Eds.) et al Dynamic economic problems with regime switches (2020)

In this paper, we tackle a generic optimal regime switching problem where the decision making process is not the same from a regime to another. Precisely, we consider a simple model of optimal switching ... [more ▼]

In this paper, we tackle a generic optimal regime switching problem where the decision making process is not the same from a regime to another. Precisely, we consider a simple model of optimal switching from competition to cooperation. To this end, we solve a twostage optimal control problem. In the first stage, two players engage in a dynamic game with a common state variable and one control for each player. We solve for open-loop strategies with a linear state equation and linear-quadratic payoffs. More importantly, the players may also consider the possibility to switch at finite time to a cooperative regime with the associated joint optimization of the sum of the individual payoffs. Using theoretical analysis and numerical exercises, we study the optimal switching strategy from competition to cooperation. We also discuss the reverse switching. [less ▲]

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See detailOptimal Timing of Carbon Capture and Storage Policies - a Social Planner's View
Chen, Yiwen; Wan, Xi; Zou, Benteng UL

E-print/Working paper (2022)

Carbon capture and storage (CCS) is considered one of the most realistic and plausible options for reducing greenhouse gas (GHG) emissions from large pollution sources. However, CCS deployment is costly ... [more ▼]

Carbon capture and storage (CCS) is considered one of the most realistic and plausible options for reducing greenhouse gas (GHG) emissions from large pollution sources. However, CCS deployment is costly. This paper considers the social cost of CCS projects and GHG damage from a central planer's point of view, providing clear information about when each player should deploy CCS. The findings are twofold: (1) given the heterogeneity of players, it is not socially optimal for all players to start CCS projects at the same time; instead, the player that has a cost advantage should start first; (2) it may be socially desirable for the player with a cost disadvantage never starts CCS. We show the conditions that support both possibilities. The second finding provides a clear policy guideline for the decision-maker: reduce the costs of the high-cost player in order to reduce global GHG emissions, provided that is the aim of the supranational institute. [less ▲]

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See detailOptimal TNFS-secure pairings on elliptic curves with composite embedding degree
Fotiadis, Georgios UL; Martindale, Chloe

E-print/Working paper (2019)

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See detailOptimal TNFS-secure pairings on elliptic curves with even embedding degree
Fotiadis, Georgios UL; Martindale, Chloe

E-print/Working paper (2018)

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See detailOptimal training sequences for joint timing synchronization and channel estimation in distributed communication networks
Nasir, Ali A.; Mehrpouyan, Hani; Durrani, Salman et al

in IEEE Transactions on Communications (2013), 7(61), 3002-3015

For distributed multi-user and multi-relay cooperative networks, the received signal may be affected by multiple timing offsets (MTOs) and multiple channels that need to be jointly estimated for ... [more ▼]

For distributed multi-user and multi-relay cooperative networks, the received signal may be affected by multiple timing offsets (MTOs) and multiple channels that need to be jointly estimated for successful decoding at the receiver. This paper addresses the design of optimal training sequences for efficient estimation of MTOs and multiple channel parameters. A new hybrid Cramer-Rao lower bound (HCRB) for joint estimation of MTOs and channels is derived. Subsequently, by minimizing the derived HCRB as a function of training sequences, three training sequence design guidelines are derived and according to these guidelines, two training sequences are proposed. In order to show that the proposed design guidelines also improve estimation accuracy, the conditional Cramer-Rao lower bound (ECRB), which is a tighter lower bound on the estimation accuracy compared to the HCRB, is also derived. Numerical results show that the proposed training sequence design guidelines not only lower the HCRB, but they also lower the ECRB and the mean-square error of the proposed maximum a posteriori estimator. Moreover, extensive simulations demonstrate that application of the proposed training sequences significantly lowers the bit-error rate performance of multi-relay cooperative networks when compared to training sequences that violate these design guidelines. [less ▲]

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See detailOptimal Two-Dimensional Lattices for Precoding of Linear Channels
Kapetanovic, Dzevdan UL; Cheng, Hei Victor; Mow, Wai Ho et al

in IEEE Transactions on Wireless Communications (2013), 12(5), 2104-2113

Consider the communication system model y = HFx+n, where H and F are the channel and precoder matrices, x is a vector of data symbols drawn from some lattice-type constellation, such as M-QAM, n is an ... [more ▼]

Consider the communication system model y = HFx+n, where H and F are the channel and precoder matrices, x is a vector of data symbols drawn from some lattice-type constellation, such as M-QAM, n is an additive white Gaussian noise vector and y is the received vector. It is assumed that both the transmitter and the receiver have perfect knowledge of the channel matrix H and that the transmitted signal Fx is subject to an average energy constraint. The columns of the matrix HF can be viewed as the basis vectors that span a lattice, and we are interested in the precoder F that maximizes the minimum distance of this lattice. This particular problem remains open within the theory of lattices and the communication theory. This paper provides the complete solution for any nonsingular M ×2 channel matrix H. For real-valued matrices and vectors, the solution is that HF spans the hexagonal lattice. For complex-valued matrices and vectors, the solution is that HF, when viewed in four-dimensional real-valued space, spans the Schlafli lattice D4. [less ▲]

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See detailOptimal V-BLAST Ordering in Fast Rayleigh Fading: A Linear Assignment Problem
Järmyr, Simon; Ottersten, Björn UL; Jorswieck, Eduard

in Signal Processing Advances in Wireless Communications (SPAWC), 2011 IEEE 12th International Workshop on (2011)

We explore a novel approach to perform decoding-order optimization in the vertical Bell Labs layered space-time (V-BLAST) architecture. Allowing for simultaneous transmission of multiple, separately ... [more ▼]

We explore a novel approach to perform decoding-order optimization in the vertical Bell Labs layered space-time (V-BLAST) architecture. Allowing for simultaneous transmission of multiple, separately encoded data streams, the V-BLAST transmit-receive scheme applies to the uplink of a multi-user communication system. A multi-antenna receiver decodes data streams successively, dealing with inter-stream interference by means of cancelling and nulling; interference from previously decoded streams is cancelled by subtraction, and remaining interference is nulled by linear equalization. The order in which the streams are decoded can have a noticeable impact on system performance. We consider the optimization of a fixed decoding order in fast Rayleigh fading, based on long-term channel-fading parameters. For a wide range of performance measures, we show that the fast-fading ordering problem can be treated as a classical linear assignment problem, allowing a solution using existing, efficient algorithms. [less ▲]

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See detailDas optimale Interface für internationale Websites: Andere Länder, anderes Design
Rohles, Björn UL

Article for general public (2016)

Interkulturelles Webdesign nimmt auf die kulturelle Prägung der Menschen Rücksicht. Die Theorie der kulturellen Dimensionen von Geert Hofstede kann helfen, die richtige Gestaltung zu wählen.

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See detailOptimality Properties and Low-Complexity Solutions to Coordinated Multicell Transmission
Björnson, Emil; Bengtsson, Mats; Ottersten, Björn UL

in Global Telecommunications Conference (GLOBECOM 2010), 2010 IEEE (2010)

Base station cooperation can theoretically improve the throughput of multicell systems by coordinating interference and serving cell edge terminals through multiple base stations. In practice, the extent ... [more ▼]

Base station cooperation can theoretically improve the throughput of multicell systems by coordinating interference and serving cell edge terminals through multiple base stations. In practice, the extent of cooperation is limited by the increase in backhaul signaling and computational demands. To address these concerns, we propose a novel distributed cooperation structure where each base station has responsibility for the interference towards a set of terminals, while only serving a subset of them with data. Weighted sum rate maximization is considered, and conditions for beamforming optimality and the optimal transmission structure are derived using Lagrange duality theory. This leads to distributed low-complexity transmission strategies, which are evaluated on measured multiantenna channels in a typical urban multicell environment. [less ▲]

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See detailOptimality Properties,Distributed Strategies, and Measurement-Based Evaluation of Coordinated Multicell OFDMA Transmission
Björnson, Emil; Jaldén, Niklas; Bengtsson, Mats et al

in IEEE Transactions on Signal Processing (2011), 59(12), 6086-6101

The throughput of multicell systems is inherently limited by interference and the available communication resources. Coordinated resource allocation is the key to efficient performance, but the demand on ... [more ▼]

The throughput of multicell systems is inherently limited by interference and the available communication resources. Coordinated resource allocation is the key to efficient performance, but the demand on backhaul signaling and computational resources grows rapidly with number of cells, terminals, and subcarriers. To handle this, we propose a novel multicell framework with dynamic cooperation clusters where each terminal is jointly served by a small set of base stations. Each base station coordinates interference to neighboring terminals only, thus limiting backhaul signalling and making the framework scalable. This framework can describe anything from interference channels to ideal joint multicell transmission. The resource allocation (i.e., precoding and scheduling) is formulated as an optimization problem (P1) with performance described by arbitrary monotonic functions of the signal-to-interference-and-noise ratios (SINRs) and arbitrary linear power constraints. Although (P1) is nonconvex and difficult to solve optimally, we are able to prove: 1) optimality of single-stream beamforming; 2) conditions for full power usage; and 3) a precoding parametrization based on a few parameters between zero and one. These optimality properties are used to propose low-complexity strategies: both a centralized scheme and a distributed version that only requires local channel knowledge and processing. We evaluate the performance on measured multicell channels and observe that the proposed strategies achieve close-to-optimal performance among centralized and distributed solutions, respectively. In addition, we show that multicell interference coordination can give substantial improvements in sum performance, but that joint transmission is very sensitive to synchronization errors and that some terminals can experience performance degradations. [less ▲]

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