Computing value correspondences for repeated games with state variables

La naturaleza de la interaccion repetida ha sido estudiada extensamente en la literatura de juegos repetidos. Abreu (1988), Abreu, Pearce y Stacchetti (1986, 1990) y Cronshaw y Luenberger (1994) desarrollan un enfoque recursivo para caracterizar juegos repetidos centrandose en los valores presentes de estrategias perfectas de subjuegos para cada jugador. Judd y Conklin (1995), Cronshaw y Rutheford (1994) y Cronshaw (1996) han implementado computacionalmente estas tecnicas. Sin embargo, algunos de los ejemplos mas interesantes de interaccion estrategica ocurren en entornos con variables de estado, en los cuales las tecnicas recursivas citadas anteriormente no pueden ser utilizadas. En dichos entornos, el conjunto de valores de equilibrio perfecto de subjuegos se vuelve funcion de la variable de estado. Este trabajo presenta un metodo general para evaluar correspondencias de equilibrio bajo vigilancia perfecta y descuento. (jc) (mac

Differential evolution to solve the lot size problem.

An Advanced Resource Planning model is presented to support optimal lot size decisions for performance improvement of a production system in terms of either delivery time or setup related costs. Based on a queueing network, a model is developed for a mix of multiple products following their own specific sequence of operations on one or more resources, while taking into account various sources of uncertainty, both in demand as well as in production characteristics. In addition, the model includes the impact of parallel servers and different time schedules in a multi-period planning setting. The corrupting influence of variabilities from rework and breakdown is explicitly modeled. As a major result, the differential evolution algorithm is able to find the optimal lead time as a function of the lot size. In this way, we add a conclusion on the debate on the convexity between lot size and lead time in a complex production environment. We show that differential evolution outperforms a steepest descent method in the search for the global optimal lot size. For problems of realistic size, we propose appropriate control parameters for the differential evolution in order to make its search process more efficient.Production planning; Lot sizing; Queueing networks; Differential evolution;

Adaptive Optics for Extremely Large Telescopes

Adaptive Optics has become a key technology for the largest ground-based telescopes currently under or close to begin of construction. Adaptive optics is an indispensable component and has basically only one task, that is to operate the telescope at its maximum angular resolution, without optical degradations resulting from atmospheric seeing. Based on three decades of experience using adaptive optics usually as an add-on component, all extremely large telescopes and their instrumentation are designed for diffraction limited observations from the very beginning. This review illuminates the various approaches of the Extremely Large Telescope, the Giant Magellan Telescope, and the Thirty-Meter Telescope, to fully integrate adaptive optics in their designs. The article concludes with a brief look into the requirements that high-contrast imaging poses on adaptive optics.Comment: 29 pages, 13 figures, published in Journal of Astronomical Instrumentation, November 2, 201

LiDAR aided simulation pipeline for wireless communication in vehicular traffic scenarios

Abstract. Integrated Sensing and Communication (ISAC) is a modern technology under development for Sixth Generation (6G) systems. This thesis focuses on creating a simulation pipeline for dynamic vehicular traffic scenarios and a novel approach to reducing wireless communication overhead with a Light Detection and Ranging (LiDAR) based system. The simulation pipeline can be used to generate data sets for numerous problems. Additionally, the developed error model for vehicle detection algorithms can be used to identify LiDAR performance with respect to different parameters like LiDAR height, range, and laser point density. LiDAR behavior on traffic environment is provided as part of the results in this study. A periodic beam index map is developed by capturing antenna azimuth and elevation angles, which denote maximum Reference Signal Receive Power (RSRP) for a simulated receiver grid on the road and classifying areas using Support Vector Machine (SVM) algorithm to reduce the number of Synchronization Signal Blocks (SSBs) that are needed to be sent in Vehicle to Infrastructure (V2I) communication. This approach effectively reduces the wireless communication overhead in V2I communication

A new estimation methodology for reusable component-based software development projects

Bibliograhy: leaves 118-121.Estimating the duration of software development projects is a difficult task. There are many factors that can derail software projects. However, estimation forms the fundamental part of planning and costing any project and is therefore very necessary. While several formal estimation methodologies exist, they all exhibit weaknesses in one form or another. The most established methodologies are based on early software development methods and it is questionable as to whether they can still address more modern development methods such as reusable component-based programming. Some researchers believe not and have proposed new methodologies that attempt to achieve this. Thus what is needed is a methodology that takes into account modern component-based development practices and, as a result, provides acceptable accuracy for the software organisation. This dissertation attempts to uniquely satisfy both of these requirements

Digital Image Access & Retrieval

The 33th Annual Clinic on Library Applications of Data Processing, held at the University of Illinois at Urbana-Champaign in March of 1996, addressed the theme of "Digital Image Access & Retrieval." The papers from this conference cover a wide range of topics concerning digital imaging technology for visual resource collections. Papers covered three general areas: (1) systems, planning, and implementation; (2) automatic and semi-automatic indexing; and (3) preservation with the bulk of the conference focusing on indexing and retrieval.published or submitted for publicatio

Adaptation of multiway-merge sorting algorithm to MIMD architectures with an experimental study

Ankara : The Department of Computer Engineering and the Institute of Engineering and Science of Bilkent University, 2002.Thesis (Master's) -- Bilkent University, 2002.Includes bibliographical references leaves 73-78.Sorting is perhaps one of the most widely studied problems of computing. Numerous asymptotically optimal sequential algorithms have been discovered. Asymptotically optimal algorithms have been presented for varying parallel models as well. Parallel sorting algorithms have already been proposed for a variety of multiple instruction, multiple data streams (MIMD) architectures. In this thesis, we adapt the multiwaymerge sorting algorithm that is originally designed for product networks, to MIMD architectures. It has good load balancing properties, modest communication needs and well performance. The multiway-merge sort algorithm requires only two all-to-all personalized communication (AAPC) and two one-to-one communications independent from the input size. In addition to evenly distributed load balancing, the algorithm requires only size of 2N/P local memory for each processor in the worst case, where N is the number of items to be sorted and P is the number of processors. We have implemented the algorithm on the PC Cluster that is established at Computer Engineering Department of Bilkent University. To compare the results we have implemented a sample sort algorithm (PSRS Parallel Sorting by Regular Sampling) by X. Liu et all and a parallel quicksort algorithm (HyperQuickSort) on the same cluster. In the experimental studies we have used three different benchmarks namely Uniformly, Gaussian, and Zero distributed inputs. Although the multiwaymerge algorithm did not achieve better results than the other two, which are theoretically cost optimal algorithms, there are some cases that the multiway-merge algorithm outperforms the other two like in Zero distributed input. The results of the experiments are reported in detail. The multiway-merge sort algorithm is not necessarily the best parallel sorting algorithm, but it is expected to achieve acceptable performance on a wide spectrum of MIMD architectures.Cantürk, LeventM.S

Unobserved components in economic time series

El trabajo se centra en situaciones en las que una variable economica puede ser descrita como la combinacion de varios componentes que no son observables (CNO). Los modelos de CNO usados en econometria y en estadistica aplicada comparten frecuentemente la misma estructura basica. Este trabajo considera modelos con este tipo de estructura. Primero, se discuten brevemente las limitaciones de filtros fijos. Se procede despues a desarrollar una metodologia general, basada en procesos estocasticos lineales, que incluye a la gran mayoria de modelos de CNO. Se analizan sucesivamente los problemas de identificacion, estimacion y diagnostico del modelo, asi como de su uso en inferencia. Se derivan a continuacion las propiedades de los estimadores preliminares y finales, asi como de los errores de estimacion y prediccion asociados. El trabajo contiene, asimismo, varias implicaciones para la investigacion econometrica empirica. (amh) (mac

Celebration Schedule 2013 (Saturday)

Full presentation schedule for Celebration, Saturday, May 4, 201

On spectrum allocation strategies in Cognitive Radio Networks

Due to the temporal and spatial underutilization of licensed spectrum bands, as well as the crowdedness of unlicensed bands, a new spectrum access paradigm has been recently proposed namely, Cognitive Radio (CR). CR enables users to adjust their transceivers\u27 frequencies depending on the availability of licensed frequency bands which are otherwise unused by their licensees, called Primary Users (PUs). Thus, unlicensed wireless users, called Secondary Users (SUs) can dynamically and opportunistically access unused licensed bands in order to improve their throughput and service reliability. Whenever the licensed users, or the PUs, become active, SUs must vacate their bands. This dissertation is concerned with the operation of Cognitive Radio Networks (CRNs), and deals with four important problems. First, a performance model to study heterogeneous channel access in CRNs is presented. In this model, there are two types of licensed channels, where one type has a larger bandwidth, and hence a higher service rate for SUs. Therefore, SUs prefer to use such channels, if available, over channels in the second type which have a lower service rate. SUs may also switch from the second to the first type of channels when they become available, even if their current channels are still available. We also model the SUs\u27 sensing process, and derive several SUs\u27 performance metrics including average waiting time. Numerical results show that our proposed operational model outperforms a baseline model that does not support prioritized access. Second, we introduce a low overhead scheme for the uplink channel allocation within a single cell of CRNs operating as Wireless Mesh Networks (CR-WMNs). The scheme does not rely on using a Common Control Channel (CCC). The proposed mechanism is based on the use of Physical Layer Network Coding (PNC), in which two (or three) Secondary Users (SUs) who are requesting uplink channel allocation are allowed to transmit synchronously over a randomly selected channel from a set of available channels, and without coordination. A Mesh Router (MR) which is listening to these transmissions, and is in charge of channel allocation, can detect up to 2 (or 3) requests, on the same channel due to the use of PNC, and replies back with a control packet which contains information about channel assignment. Our proposed mechanisms significantly outperform traditional schemes that rely on using one CCC, or do not use PNC, in terms of channel allocation overhead time. Third, we also propose to enable SUs to recover their packets which collide with PUs\u27 transmissions when a PU becomes active for two scenarios, based on the received phase shifts. When a collision occurs between an SU and a PU transmitters, the SU\u27s receiver considers the PU\u27s transmission as an interference, and hence, cancels its effect in order to recover its corresponding received packet\u27s signals. Recovering collided packets, instead of retransmitting them saves transmitters\u27 energy. Numerical results show that a high percentage of energy can be saved over the traditional scheme, in which our packets recovery mechanisms are not employed. Finally, we propose a novel multicast resilient routing approach to select primary and backup paths from an SU source to SUs destinations. Our approach employs a multilayer hyper-graph, in order to model the network, e.g., channels. The primary paths to destination SUs are selected to minimize the end-to-end delay which takes into consideration channels switching latency and transmission delay. To protect the multicast session, we find a backup path for primary path, if feasible, such that these two paths are shared risk hyper-edge disjoint, in order to prevent a concurrent failure for these two paths, when the corresponding PU for this hyper-edge becomes active. Our simulation results show that increasing the number of available channels, increase the number of feasible primary and backup paths, and the maximum path delay decreases almost linearly