Bin Packing and Related Problems: General Arc-flow Formulation with Graph Compression

We present an exact method, based on an arc-flow formulation with side constraints, for solving bin packing and cutting stock problems --- including multi-constraint variants --- by simply representing all the patterns in a very compact graph. Our method includes a graph compression algorithm that usually reduces the size of the underlying graph substantially without weakening the model. As opposed to our method, which provides strong models, conventional models are usually highly symmetric and provide very weak lower bounds. Our formulation is equivalent to Gilmore and Gomory's, thus providing a very strong linear relaxation. However, instead of using column-generation in an iterative process, the method constructs a graph, where paths from the source to the target node represent every valid packing pattern. The same method, without any problem-specific parameterization, was used to solve a large variety of instances from several different cutting and packing problems. In this paper, we deal with vector packing, graph coloring, bin packing, cutting stock, cardinality constrained bin packing, cutting stock with cutting knife limitation, cutting stock with binary patterns, bin packing with conflicts, and cutting stock with binary patterns and forbidden pairs. We report computational results obtained with many benchmark test data sets, all of them showing a large advantage of this formulation with respect to the traditional ones

Performance Evaluation of Low Complexity Massive MIMO Techniques for SC-FDE Schemes

Massive-MIMO technology has emerged as a means to achieve 5G's ambitious goals; mainly to obtain higher capacities and excellent performances without requiring the use of more spectrum. In this thesis, focused on the uplink direction, we make a study of performance of low complexity equalization techniques as well as we also approach the impact of the non-linear elements located on the receivers of a system of this type. For that purpose, we consider a multi-user uplink scenario through the Single Carrier with Frequency Domain Equalization (SC-FDE) scheme. This seems to be the most appropriate due to the low energy consumption that it implies, as well as being less favorable to the detrimental effects of high envelope fluctuations, that is, by have a low Peak to Average Power Ratio (PAPR) comparing to other similar modulations, such as the Orthogonal Frequency Division Multiplexing (OFDM). Due to the greater number of antennas and consequent implementation complexity, the equalization processes for Massive- MIMO schemes are aspects that should be simplified, that is, they should avoid the inversion of matrices, contrary to common 4G, with the Zero Forcing (ZF) and Minimum Mean Square Error (MMSE) techniques. To this end, we use low-complexity techniques, such as the Equal Gain Combining (EGC) and the Maximum Ratio Combining (MRC). Since these algorithms are not sufficiently capable of removing the entire Inter-Symbol Interference (ISI) and Inter-User Interference (IUI), we combine them with iterative techniques, namely with the Iterative Block with Decision Feedback Equalizer (IB-DFE) to completely remove the residual ISI and IUI. We also take into account the hardware used in the receivers, since the effects of non-linear distortion can impact negatively the performance of the system. It is expected a strong performance degradation associated to the high quantization noise levels when implementing low-resolution Analog to Digital Converters (ADCs). However, despite these elements with these configurations become harmful to the performance of the majority of the systems, they are considered a desirable solution for Massive-MIMO scenarios, because they make their implementation cheaper and more energy efficient. In this way, we made a study of the impact in the performance by the low-resolution ADCs. In this thesis we suggest that it is possible to bypass these negative effects by implementing a number of receiving antennas far superior to the number of transmitting antennas

Recapitalization of Caixa Geral de Depósitos

This thesis presents a case study about the 2017 recapitalization of Portuguese bank Caixa Geral de Depósitos (CGD). The case starts by presenting CGD’s situation and what led to its urgent capital needs. Furthermore, the case presents an analysis of new capital regulations coming out of Basel III and how banks use a combination of hybrid securities such as Contingent Convertible and Perpetual Notes to comply with such regulations. Finally, there is an in depth analysis of the recent issuance of Additional Tier 1 Capital Write Down Notes by CGD, and what it represents to the state owned bank’s futur

The ethnomathematics of a Fishing Community at Câmara de Lobos in Portugal

The mathematics education research community has been discussing the issue of the connections between mathematics and culture. This is the main concern underneath this work, as it tries to reveal everyday life mathematics of a fishing community in Câmara de Lobos, Madeira, Portugal. The study followed a qualitative approach based on an ethnographic model. In order to collect data the researcher remained during long periods of time in the field, using participant observation, interviews, photographic and video registers and document collection. Data analysis was of an interpretative nature. We focus here on the mathematical notions of ratio and fraction and how they are used within the community, especially by one caulker living there.A comunidade de Investigação em Educação Matemática tem vindo a discutir as conexões entre a matemática e a cultura. Esta é a preocupação por detrás deste trabalho, que tenta revelar as práticas matemáticas do quotidiano de uma comunidade piscatória em Câmara de Lobos, Madeira, Portugal. Este estudo seguiu uma linha qualitativa baseada num modelo etnográfico. De forma a coligir dados, o investigador permaneceu durante longos períodos de tempo no local, usando observação participante, entrevistas, registos fotográficos e vídeo e recolha de documentos. A análise de dados seguiu uma linha interpretativa. Neste artigo, acabamos por focar nas noções matemáticas de fracção e razão e como são usadas na comunidade, em especial pelo calafate desta comunidade piscatória.CIEC - Centro de Investigação em Estudos da Criança, IE, UMinho (UI 317 da FCT), PortugalFundos Nacionais através da FCT (Fundação para a Ciência e a Tecnologia) e cofinanciado pelo Fundo Europeu de Desenvolvimento Regional (FEDER) através do COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) com a referência POCI-01-0145-FEDER-007562info:eu-repo/semantics/publishedVersio

(Ethno)mathematical tasks in the context of proportional reasoning

Investigating mathematical knowledge used in everyday contexts of fishing communities has been our area of interest in mathematics education. Initially we investigated the fishing community of Câmara de Lobos (Madeira - Portugal) and later we also investigated the largest Portuguese fishing community (Caxinas - Vila do Conde in the North of Portugal). The initial purpose was to collect everyday mathematical knowledge of these fishing communities and then contextualize it within the curriculum documents that guide mathematics teaching. A second purpose was the development of mathematical tasks based on the information previously gathered from these fishing communities, for future use in the classroom.CIEC – Research Centre on Child Studies, IE, UMinho (FCT R&D unit 317), PortugalNational Funds through the FCT (Foundation for Science and Technology) and co-financed by European Regional Development Funds (FEDER) through the Competitiveness and Internationalization Operational Program (POCI) with the reference POCI-01-0145-FEDER-007562info:eu-repo/semantics/publishedVersio

Recommender system for drivers of electric vehicles

Being the next big step in automobile industry, electric vehicles continue to have limited autonomy which associated with the long charging times, limited charging stations and undeveloped smart grid infrastructure demands for a hard planning of the daily use of the vehicle. This paper presents an information system that will help the driver in the daily use of his electric vehicle, minimizing the problem of range anxiety thru the continuous control of the vehicle range and presenting in time relevant information about the charging stations within reach. Given the success of recommendation systems on automatically delivering the relevant information in numerous areas of usage, it can be applied in this scenario as well as with the objective of maximizing the relevance of the information presented to the driver, which should be the strictly needed for him to make his decisions filtering out the unnecessary one.Fundação para a Ciência e a Tecnologia (FCT

Intelligent decision support for university application using RIASEC codes

A study performed recently in Portugal showed that there are currently about 320,000 students attending high school. Typically, 51 % of them didn’t know concretely which course to select, five months before the application date. A significant number (about 160,000) of students needed to be guided and informed about the educational provision at the national level. In addition, 25% of the approximately 309,000 students attending Portuguese Public Higher Education (about 77,000) have changed or thought about changing course during their academic career due to some dissatisfaction related to the current course. In order to minimize these difficulties a decision model was outlined. The solution is based on the construction of a tool that, through a carefully prepared questionnaire, will identify what are the best alternatives for students’ application. Key information has been collected from the analysis of several variables in various contexts (e.g. social, economic, personal, and psychological), from scientific studies and from real facts. The resulting model is a weighted model where variables can be set by the user in order to guide the decision making process. Therefore the model is able to adapt to the intrinsic characteristics of each user. This paper focuses in the psychometric capability of the solution (which is unique in this environment) adopting the RIASEC Codes (domains) as the vocational component of the decision model

O planeamento de reabilitações orais utilizando um articulador virtual

Dissertação para obtenção do grau de Mestre no Instituto Universitário Egas MonizO articulador é um dispositivo mecânico que simula as articulações temporomandibulares, a mandíbula e a maxila. Os modelos superiores e inferiores das arcadas dentárias do paciente são montados neste dispositivo para simular alguns ou todos os movimentos mandibulares. Devido à impossibilidade de o paciente estar presente em todas as fases do estudo (diagnóstico, planeamento e execução laboratorial dos trabalhos), os articuladores foram criados com o objetivo de auxiliar os profissionais na pesquisa, no estudo, na análise funcional das relações estáticas e dinâmica, na oclusão dentária, na articulação temporomandibular e na confeção de próteses dentárias dentro da complexidade do aparelho estomatognático. Vários modelos de articuladores foram criados para estas finalidades, sendo que esta variedade de modelos torna possível a seleção de um instrumento que satisfaça, dentro de limitações específicas, as necessidades clínicas de cada caso. Com a atual tendência para medicina dentária digital, o “digital clinician” deve perceber como implementar e manusear um articulador digital na prática diária. No campo da medicina dentária reabilitadora e restauradora, o articulador digital apresenta aplicações da realidade virtual no mundo da prática clínica para a análise do complexo estático e dinâmico das relações oclusais. O articulador virtual tem a capacidade de simular movimentos específicos de mastigação do paciente. O programa prevê os locais onde os dentes oponentes vão estar em contato. É de referir que, sem os dados específicos do paciente inseridos no programa, um articulador digital vai ter o mesmo comportamento que um articulador tradicional. Estudos feitos para verificar a veracidade do articulador virtual apresentam correspondência positiva na simulação do número e posições dos contactos dinâmicos dos dentes. É um instrumento preciso para a análise da oclusão em pacientes, podendo ajudar o profissional a estabelecer um diagnóstico e planear a melhor opção de tratamento.The articulator is a mechanical device that replicates the temporomandibular joints, the mandible and the maxilla. The upper and lower models of the patient's dental arches are mounted on this device to simulate some or all the mandibular movements. Due to the impossibility of the patient to be present in all phases of the study (diagnosis, planning and laboratory execution of the work), the articulators were created with the objective of assisting the professionals in the research, in the study, in the functional analysis of the static and dynamic relationships, in the dental occlusion, in the temporomandibular joint and in the confection of dental prostheses within the complexity of the stomatognathic apparatus. Several articulator models have been created for these purposes, and this variety of models makes it possible to select an instrument that meets, within specific limitations, the clinical needs of each case. With the current trend towards digital dental medicine, the "digital clinician" should understand how to implement and handle a digital articulator in its daily practice. In the field of rehabilitative and restorative dental medicine, the digital articulator presents applications of virtual reality in the world of clinical practice for the analysis of the static and dynamic complex of occlusal relationships. The virtual articulator can simulate specific mastication movements of the patient. The program predicts the locations where the opposing teeth will be in contact. It should be noted that without the specific patient data inserted in the program, a digital articulator will have the same behavior as a traditional articulator. Several studies to verify the veracity of the virtual articulator show positive correspondence in the simulation of the number and positions of dynamic contacts of teeth. It is an accurate instrument for occlusion analysis in patients and can help the professional establish a diagnosis and plan the best treatment option