Alejandro López‐Ortiz

Centro de Investigación en Materiales Avanzados

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

V. Collins-Martı́nez

Centro de Investigación en Materiales Avanzados

Reza Dorrigiv

Samsung (United States)

Shahin Kamali

York University

Alejandro Salinger

Systems, Applications & Products in Data Processing (Germany)

J. Ian Munro

University of Waterloo

Jesús Salinas Gutiérrez

Centro de Investigación en Materiales Avanzados

Miguel A. Escobedo-Bretado

Universidad Juárez del Estado de Durango

Erik D. Demaine

Vassar College

Virginia Hidalina Collins Martinez

Jesús M. Salinas-Gutiérrez

Centro de Investigación en Materiales Avanzados

Cooperative Institutions

University of Waterloo

Centro de Investigación en Materiales Avanzados

Saarland University

University of Alberta

Concordia University

University of Windsor

Concordia University

University of Regina

Centre National de la Recherche Scientifique

Max Planck Society

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Optimal Distributed Searching in the Plane with and Without Uncertainty

Lecture notes in computer science (2016)

Alejandro López‐Ortiz Daniela Maftuleac

Visibility

Search and rescue

Drone

Search problem

10.1007/978-3-319-30139-6_6

Cite

Citations (2)

Redox Stabilization Effect of TiO2 in Co3O4 as Oxygen Carrier for the Production of Hydrogen through POX and Chemical Looping Processes

International Journal of Chemical Reactor Engineering (2005)

Thelma De los Rios Daniel Lardizábal‐Gutiérrez V. Collins Martínez Alejandro López‐Ortiz

Novel proposed processes for H2 production and energy generation such as partial oxidation of hydrocarbons (POX-MeO) and chemical looping process (CLP), respectively require the use of solid oxides as oxygen carriers. In POX-MeO the required oxygen for the partial oxidation of methane is provided by a transition metal oxide (MeO). First, H2 is produced through CH4+MeO = CO+H2+Me. Secondly, Me is re-oxidized through Me+O2 = MeO to regenerate the oxygen carrier. In the CL process, CH4 is being completely oxidized through CH2 + MeO = CO2 + H2O + Me producing heat and CO2 ready for sequestration. Finally, Me is re-oxidized using air to regenerate the Me back to MeO. In both processes the regenerated MeO is sent back to the initial step to result in a cyclic operation. Continuous exposure of MeO to Redox cycles frequently produces sinterization and MeO stabilization is needed to avoid loss of activity. The objective of this study is to investigate the stabilization effect of TiO2 in Co3O4 during Redox cycles to be used as an oxygen carrier using CoxTiOy type spinnels. Characterization of the synthesized samples included XRD, TPR, and SEM. Co2TiO4 and CoTiO3 spinnels were synthesized by solid state reaction. TGA and TPR Redox performance cycles of Co3O4 produced sintering, while results using a Co2TiO4 spinnel structure suggest a strong stabilization effect of TiO2 on Co. Ten Redox cycles using H2 and CH4 as reducing agents and a mixture of O2/N2 as oxidizer resulted in fixation of Co to TiO2 avoiding sintering.

Chemical-Looping Combustion

Partial oxidation

Reducing agent

10.2202/1542-6580.1260

Cite

Citations (7)

Online Scheduling FIFO Policies with Admission and Push-Out

Theory of Computing Systems (2015)

Kirill Kogan Alejandro López‐Ortiz Sergey Nikolenko Alexander Sirotkin

Competitive Analysis

Online algorithm

10.1007/s00224-015-9626-4

Cite

Citations (16)

Broadcasting in Conflict-Aware Multi-channel Networks

Lecture notes in computer science (2013)

Francisco Claude Reza Dorrigiv Shahin Kamali Alejandro López‐Ortiz Paweł Prałat

10.1007/978-3-642-36065-7_16

Cite

Citations (2)

Adaptive Searching in One and Two Dimensions

Canadian Conference on Computational Geometry (2008)

Reza Dorrigiv Alejandro López‐Ortiz

Source

Cite

Citations (2)

The Within-Strip Discrete Unit Disk Cover Problem.

Canadian Conference on Computational Geometry (2012)

Robert Fraser Alejandro López‐Ortiz

We present a study of the Within-Strip Discrete Unit Disk Cover (WSDUDC) problem, which is a restricted version of the Discrete Unit Disk Cover (DUDC) problem. For the WSDUDC problem, there exists a set of points and a set of unit disks in the plane, and the points and disk centres are conned to a strip of xed height. An optimal solution to the WSDUDC problem is a set of disks of minimum cardinality that covers all points in the input set. We describe a range of approximation algorithms for the problem, including 4- and 3-approximate algorithms which apply for strips of height 2 p 2=3 0:94 and 0:8 units respectively, as well as a general scheme for any strip with less than unit height. We prove that the WSDUDC problem is NP-complete on strips of any xed height, which is our most interesting result from a theoretical standpoint. The result is also quite surprising, since a number of similar problems are tractable on strips of xed height. Finally, we discuss how these results may be applied to known DUDC approximation algorithms.

STRIPS

Cardinality (data modeling)

Set cover problem

Unit disk

Unit disk graph

Source

Cite

Citations (10)

Searching and on-line recognition of star-shaped polygons

Information and Computation (2003)

Alejandro López‐Ortiz Sven Schuierer

Polygon (computer graphics)

Star (game theory)

Competitive Analysis

Line (geometry)

Rectilinear polygon

Visibility polygon

10.1016/s0890-5401(03)00081-6

Cite

Citations (3)

Going home through an unknown street

Lecture notes in computer science (1995)

Alejandro López‐Ortiz Sven Schuierer

Competitive Analysis

Traverse

Visibility

Polygon (computer graphics)

Cross-ratio

10.1007/3-540-60220-8_57

Cite

Citations (22)

An experimental investigation of set intersection algorithms for text searching

ACM Journal of Experimental Algorithmics (2009)

Jérémy Barbay Alejandro López‐Ortiz Tyler Lu Alejandro Salinger

The intersection of large ordered sets is a common problem in the context of the evaluation of boolean queries to a search engine. In this article, we propose several improved algorithms for computing the intersection of sorted arrays, and in particular for searching sorted arrays in the intersection context. We perform an experimental comparison with the algorithms from the previous studies from Demaine, López-Ortiz, and Munro [ALENEX 2001] and from Baeza-Yates and Salinger [SPIRE 2005]; in addition, we implement and test the intersection algorithm from Barbay and Kenyon [SODA 2002] and its randomized variant [SAGA 2003]. We consider both the random data set from Baeza-Yates and Salinger, the Google queries used by Demaine et al., a corpus provided by Google, and a larger corpus from the TREC Terabyte 2006 efficiency query stream, along with its own query log. We measure the performance both in terms of the number of comparisons and searches performed, and in terms of the CPU time on two different architectures. Our results confirm or improve the results from both previous studies in their respective context (comparison model on real data, and CPU measures on random data) and extend them to new contexts. In particular, we show that value-based search algorithms perform well in posting lists in terms of the number of comparisons performed.

Randomized Algorithm

10.1145/1498698.1564507

Cite

Citations (71)

On the list update problem with advice

Information and Computation (2016)

Joan Boyar Shahin Kamali Kim S. Larsen Alejandro López‐Ortiz

Competitive Analysis

Advice (programming)

Online algorithm

Deterministic algorithm

Argument (complex analysis)

10.1016/j.ic.2016.06.007

Cite

Citations (9)