Presentations of Noneffective Orbifolds

It is well-known that an effective orbifold M (one for which the local stabilizer groups act effectively) can be presented as a quotient of a smooth manifold P by a locally free action of a compact lie group K. We use the language of groupoids to provide a partial answer to the question of whether a noneffective orbifold can be so presented. We also note some connections to stacks and gerbes.Comment: 19 page

Bicommutant categories from fusion categories

Bicommutant categories are higher categorical analogs of von Neumann algebras that were recently introduced by the first author. In this article, we prove that every unitary fusion category gives an example of a bicommutant category. This theorem categorifies the well known result according to which a finite dimensional *-algebra that can be faithfully represented on a Hilbert space is in fact a von Neumann algebra.Comment: Updated to the published version + fixed some small typo

To surcharge or not to surcharge? A two-sided market perspective of the no-surchage rule

In Electronic Payment Networks (EPNs) the No-Surcharge Rule (NSR) requires that merchants charge the same final good price regardless of the means of payment chosen by the customer. In this paper, we analyze a three-party model (consumers, merchants, and proprietary EPNs) to assess the impact of a NSR on the electronic payments system, in particular, on competition among EPNs, network pricing to merchants and consumers, EPNs' profits, and social welfare. We show that imposing a NSR has a number of effects. First, it softens competition among EPNs and rebalances the fee structure in favor of cardholders and to the detriment of merchants. Second, we show that the NSR is a profitable strategy for EPNs if and only if the network e¤ect from merchants to cardholders is sufficiently weak. Third, the NSR is socially (un)desirable if the network externalities from merchants to cardholders are sufficiently weak (strong) and the merchants' market power in the goods market is sufficiently high (low). Our policy advice is that regulators should decide on whether the NSR is appropriate on a market-by-market basis instead of imposing a uniform regulation for all markets. JEL Classification: L13, L42, L80American Express, Discover, Electronic payment system, market power, MasterCard, network externalities, no-surcharge rule, regulation, two-sided markets, Visa

Categorified trace for module tensor categories over braided tensor categories

Given a braided pivotal category $\mathcal C$ and a pivotal module tensor category $\mathcal M$, we define a functor $\mathrm{Tr}_{\mathcal C}:\mathcal M \to \mathcal C$, called the associated categorified trace. By a result of Bezrukavnikov, Finkelberg and Ostrik, the functor $\mathrm{Tr}_{\mathcal C}$ comes equipped with natural isomorphisms $\tau_{x,y}:\mathrm{Tr}_{\mathcal C}(x \otimes y) \to \mathrm{Tr}_{\mathcal C}(y \otimes x)$, which we call the traciators. This situation lends itself to a diagramatic calculus of `strings on cylinders', where the traciator corresponds to wrapping a string around the back of a cylinder. We show that $\mathrm{Tr}_{\mathcal C}$ in fact has a much richer graphical calculus in which the tubes are allowed to branch and braid. Given algebra objects $A$ and $B$, we prove that $\mathrm{Tr}_{\mathcal C}(A)$ and $\mathrm{Tr}_{\mathcal C}(A \otimes B)$ are again algebra objects. Moreover, provided certain mild assumptions are satisfied, $\mathrm{Tr}_{\mathcal C}(A)$ and $\mathrm{Tr}_{\mathcal C}(A \otimes B)$ are semisimple whenever $A$ and $B$ are semisimple.Comment: 49 pages, many figure

Access prices indexed to geographical coverage of innovative telecom services

The literature on access prices and investment has suggested that firms under-invest when subject to an access provision obligation combined with a fixed access price per consumer. In this paper, I study an access price per consumer for an innovative service such as super- fast broadband provided by a regulated firm that is a function of its geographical coverage (indexation approach). The indexation approach can enhance economic efficiency beyond what is achieved with a fixed access price under a set of standard assumptions. In particular, it can simultaneously induce the firms to set lower retail prices, lead to wider geographi- cal coverage of innovative services and higher social welfare level compared with a fixed access price. Moreover, in the model, the indexation may be used to achieve approximately the Ramsey outcome, or the first-best coverage level. I address how a regulator can set the access price indexation optimally, based on the coverage cost plus an incentive. I highlight the potential role of indexation as a tool to reduce the need for public subsidies and the associated tax distortions when compared with a fixed access price

IT governance enablers for an efficient IoT implementation

IoT is considered to be one of the focal points for the 4.0 industry revolution because of the way it is changing the business models of each organization. IT governance is now an increasingly important tool for organizations to align their IT infrastructure with the organization's business objectives. IT governance has been used to help implement new technologies using the best practices such as COBIT, which defines a number of enablers that facilitate the implementation, identification and management of IT. This research aims to explore and define the most suitable enablers for an IoT implementation. These objectives will be achieved through the Design Science Research methodology, which incorporates two literature reviews, a Delphi method and, finally, a semi-structured interview. With a first systematic review of the literature, it was possible to identify the main enablers to implement IoT. Next, the list was improved using the Delphi method, gathering expert opinion. In the Delphi method, the level of agreement was verified to create exclusion criteria and a level of efficiency in each recommendation. Finally, a specialist was interviewed to demonstrate the applicability and validation of the proposed artifact in the various IoT projects implemented by his organization. At the end, a final list of enablers for IoT implementation is provided. The results indicate that data privacy, data protection, and data analysis are currently the best recommendations to be considered in an IoT implementation because they increase the efficiency of the solution and increase the credibility of the data obtained. Future work and limitations are detailed in the end.A IoT é considerada como um dos pontos fulcrais para a revolução da indústria 4.0, devido à maneira como está a alterar os modelos de negócio das organizações. A governação das TI é atualmente uma ferramenta cada vez mais importante para as organizações alinharem a sua infraestrutura tecnológica com os objetivos de negócio da organização. A governação de TI tem sido utilizada para ajudar na implementação de novas tecnologias recorrendo à utilização de boas práticas como por exemplo o COBIT, que define vários enablers que facilitam a implementação, identificação e gestão das TI. Esta investigação visa explorar e definir os enablers mais adequados para uma implementação de IoT. Estes objetivos vão ser alcançados através da metodologia Design Science Research, que incorpora duas revisões de literatura, um método Delphi e por fim uma entrevista semiestruturada. Com uma primeira revisão sistemática da literatura, foi possível identificar os principais enablers para implementar IoT. De seguida, a lista foi melhorada utilizando o método Delphi, recolhendo a opinião de especialistas. No método Delphi, verificou-se o nível de concordância para criar critérios de exclusão e um nível de eficiência em cada recomendação. Finalmente, um especialista foi entrevistado para demonstrar a aplicabilidade e validar o artefacto proposto nos diversos projetos de IoT implementados pela sua organização. No final a lista de enablers para implementar IoT é fornecida. Os resultados indicam que atualmente, a privacidade de dados, a proteção de dados e a análise de dados são as melhores recomendações a serem consideradas numa implementação de IoT, porque aumentam a eficiência da solução e aumentam a credibilidade dos dados obtidos. Trabalho futuro e limitações são detalhadas no final

Development of a device for kinematic and electromyographyic analysis of the upper limb in a clinical context

Stroke is a leading cause of disability worldwide, significantly impacting individuals ability to perform Activities of Daily Living (ADL). Therapists assess patients limb functionality through observation and personal opinion in order to develop recovery plans. However, these plans may not always align with the patient’s specific needs. The examination of limb functional- ity using Electromiograpy (EMG) and kinematic parameters during ADL presents additional behavioral parameters. This allows for the development of personalized plans based on indi- vidual patient needs. Nevertheless, limited studies combine these two parameters to evaluate limb functionality during ADL, creating a knowledge gap in this area. This project aims to develop a prototype of a device capable of acquiring EMG and kinematic data, namely ac- celeration and angular velocity via an Inertial Measurement Unit, focusing on the shoulder complex, for use in a clinical setting. Additionally, an interface has been developed for commu- nication and visualization of the collected data. To assess the device’s performance, samples were obtained from healthy individuals performing the ADL of "Drinking water from a cup", while acquiring EMG data from the Andterior Delotoid and the raw angular velocity and accel- eration. The data relating to electromyographic activity and acceleration in the X and Y axes were compared with the results obtained in a previous work, which is still under development, in which a reference device was used. The EMG graphs are quite similar, being characterized by three peaks, while those of acceleration on the X and Y axes also show similar behavior between both works. Regarding AV, it is possible to conclude that certain movements mainly affect certain axes, namely, the X axis is affected by abduction and adduction movements, Y by rotations and Z by flexion and extension movements. The results obtained allowed to conclude that the prototype is capable of collecting data, which are quite similar to those obtained with a reference device.O Acidente Vascular Cerebral é uma das principais causas de incapacidade a nível global, afe- tando o nível de vida das pessoas na execução de Atividades da Vida Diária (AVD). A avaliação da funcionalidade dos membros é feita por terapeutas que recorrem à observação e opinião pessoal para elaboração de planos de recuperação para os doentes. No entanto, estes planos nem sempre correspondem às necessidades específicas dos pacientes. O estudo da funcionali- dade do membro com recurso a Eletromiografia (EMG) e parâmetros cinemáticos na execução de AVD fornece mais parâmetros sobre o comportamento deste, sendo então possível estabe- lecer planos mais personalizados de acordo com as necessidades de cada paciente. Contudo, são poucos os estudos em que estes dois parâmetros são utilizados para avaliar a funciona- lidade do membro na execução de AVD, pelo que há uma lacuna neste aspeto. Este projeto tem o objetivo de desenvolver um protótipo de um dispositivo capaz de recolher dados EMG e cinemáticos do complexo do ombro, nomeadamente aceleração e velocidade angular, com recurso a uma Unidade de Medição Inercial, com o objetivo de ser aplicado num contexto clí- nico. Uma interface também foi criada para comunicação e visualização dos dados recolhidos pelo dispositivo. De modo a avaliar o desempenho do dispositivo, foram feitas recolhas em indivíduos saudáveis da AVD "Beber água de um copo", adquirindo dados de EMG do Deltóide Anterior e a velocidade angular e aceleração. Os dados relativos à àtividade eletromiográfica e à aceleração nos eixos X e Y foram comparados com os resultados obtidos num trabalho anterior, que ainda se encontra em desenvolvimento, no qual foi utilizado um dispositivo de referência. Os gráficos de EMG são bastante semelhantes, sendo este caracterizado por três picos, enquanto os da aceleração nos eixos X e Y também apresentam um comportamento semelhante entre ambos os trabalhos. Relativamente à VA é possível concluir que certos mo- vimentos afetam maioritariamente certos eixos, nomeadamente, eixo do X é afetado pelos movimentos de abdução e adução, Y pelas rotações e Z pelos movimentos de flexão e exten- são. Os resultados obtidos permitiram concluir que o protótipo é capaz de recolher dados, sendo estes bastante semelhantes aos obtidos com um dispositivo de referência

To Surcharge or Not To Surcharge? A Two-Sided Market Perspective of the No-Surcharge Rule

In Electronic Payment Networks (EPNs) the No-Surcharge Rule (NSR) requires that merchants charge the same nal good price regardless of the means of payment chosen by the customer. In this paper, we analyze a three-party model (consumers, merchants, and proprietary EPNs) to assess the impact of a NSR on the electronic payments system, in particular, on competition among EPNs, network pricing to merchants and consumers, EPNs pro ts, and social welfare. We show that imposing a NSR has a number of e¤ects. First, it softens competition among EPNs and rebalances the fee structure in favor of cardholders and to the detriment of merchants. Second, we show that the NSR is a pro table strategy for EPNs if and only if the network e¤ect from merchants to cardholders is su¢ ciently weak. Third, the NSR is socially (un)desirable if the network externalities from merchants to cardholders are su¢ ciently weak (strong) and the merchants market power in the goods market is su¢ ciently high (low). Our policy advice is that regulators should decide on whether the NSR is appropriate on a market-by-market basis instead of imposing a uniform regulation for all markets