On Frequency-Domain Implementation of Digital FIR Filters Using Overlap-Add and Overlap-Save Techniques

In this paper, new insights in frequency-domain implementations of digital finite-length impulse response filtering (linear convolution) using overlap-add and overlap-save techniques are provided. It is shown that, in practical finite-wordlength implementations, the overall system corresponds to a time-varying system that can be represented in essentially two different ways. One way is to represent the system with a distortion function and aliasing functions, which in this paper is derived from multirate filter bank representations. The other way is to use a periodically time-varying impulse-response representation or, equivalently, a set of time-invariant impulse responses and the corresponding frequency responses. The paper provides systematic derivations and analyses of these representations along with filter impulse response properties and design examples. The representations are particularly useful when analyzing the effect of coefficient quantizations as well as the use of shorter DFT lengths than theoretically required. A comprehensive computational-complexity analysis is also provided, and accurate formulas for estimating the optimal DFT lengths for given filter lengths are derived. Using optimal DFT lengths, it is shown that the frequency-domain implementations have lower computational complexities (multiplication rates) than the corresponding time-domain implementations for filter lengths that are shorter than those reported earlier in the literature. In particular, for general (unsymmetric) filters, the frequency-domain implementations are shown to be more efficient for all filter lengths. This opens up for new considerations when comparing complexities of different filter implementations.Comment: 13 pages, 26 figure

Initiating a Smart Tourism Ecosystem: A Public Actor Perspective

Smart tourism ecosystems are an emerging phenomenon; however, how these ecosystems are initiated by city actors is under-explored in the existing literature. In this paper, we conduct a qualitative case study to investigate the initiation of a de novo smart tourism ecosystem in the City of Gothenburg—the European capital of smart tourism 2020. Göteborg & Co, as a public organization, is initiating a digital Destination Data Platform (DDP) as the core of its tourism ecosystem and is working on involving non-focal actors to shape the surrounding ecosystem. Our findings extend the existing research on innovation ecosystems by highlighting a hybrid public-private focal actor in the smart tourism ecosystem. We also underline how a public focal actor leverages its unique public position and legal obligations to involve non-focal actors and orchestrating the ecosystem. Finally, we suggest a conceptual model for a smart tourism ecosystem focusing on the place and purpose of control points

L'état chinois en action

La Chine est en train de changer la politique mondiale. Comprendre les formes de son gouvernement relève d’une impérieuse nécessité. Le 4e plénum du comité central du Parti communiste chinois (PCC), réuni à Pékin fin octobre 2014, a consacré ses travaux à la promotion de l’État de droit. Le document issu de cette réunion indique qu’il s’agit « d’accélérer l’édification d’un système de gouvernance par la loi », en réponse aux dérives attestées de celui-ci : inégalités sociales, corruption, abus de pouvoir et dénis de justice. [Premières lignes

Transnationell kooperation

Farmers Cooperative has in recent years developed from national markets to cross-border, international, collaborations. One example is the merger between the Swedish dairy company Arla and Danish MD Foods, where the companies collectively are sought to reduce transaction costs and thus improve efficiency. The Swedish market for commodities (fertilizers and pesticides) in agriculture has for many years been dominated by a few large players, with little opportunity for grain associations and local grain companies to offer their customers a varied range of commodities with a competitive pricing. To change this state, a majority of Swedish and Danish grain associations and local grain companies have established a trans-national cooperation. Through the establishment of the organization DLA Agro, they offer their customers a good variety of products with competitive prices. This study investigates thus according to the theory of cooperative models to what extent and how the DLA Agro helps to create benefits for the Swedish member companies. Crucial to this analysis is to DLA Agro's special organizational features can be expected to have significant bearing on the transaction and agency costs, which member companies are experiencing. Organizational features means that it is a federal organization and that it is trans-national cooperation, which has consequences for the financing, governance and operations. The method for conducting the survey consists of qualitative interview techniques with detailed interviews of every Swedish association and companies connected to the DLA Agro. The interviews indicate that members largely feel that the DLA Agro has a good relationship with the Swedish member group. The fact that the member group is relatively small in number and largely homogeneous with regard to the benefits members want out of it helps to contribute to the cooperation. Also that DLA Agro has a limited business portfolio with few products makes it easier for the cooperation to focus on reducing transaction costs. An important factor explaining the success of the cooperation is that it does not store any collective capital within the DLA Agro. This facilitates control of the DLA Agro, as potential conflict of interest on what the collective capital is to be invested in reduces. The fact that DLA Agro has inscribed in the statutes that members must sign a declaration of loyalty and the obligation to purchase ensures DLA Agro that the members will purchase every year. By doing so the risk of getting passive members with too divergent business interests reduces. The survey also shows that future conflicts may arise. This is because a number of respondents would like the opportunity to trade in seeds. This could cause problems because a number of the members in the Swedish member group are also grain producers

Svenska exportkrigare i Syrien.

Syftet med denna uppsats är att karaktärisera de svenskar som väljer att delta i kriget i Syrien, samt analysera hur dessa samorganiserar sig. Detta för att skapa en klarare bild kring vad som kännetecknar en exportkrigare, samt hur en sådan verksamhet rent praktiskt kan se ut. Dessa frågor strävar vi efter att besvara utifrån tre teoretiska ramverk där var och en används för att skapa förståelse gällande centrala faktorer såsom individuell radikalisering samt organisatoriska strukturer och mål inom våldsbejakande extremistgrupper. I vår studie kom vi fram till att de mest tydliga karaktärsdragen hos svenskarna var en upplevt kollektiv plikt att delta i konflikten för Islams räkning, oftast som följd av att de kommit i kontakt med en radikaliserande social kontext. Denna sociala kontext verkar i vårt fall ha förstärkts genom användandet av sociala medier vilket även underlättar samorganiseringen av dessa individer

Ungdomars och unga vuxnas egna uppfattningar om alkohol och narkotikabruk : En kvalitativ studie

Young people’s and young adults’ own perceptions of alcohol- and drug use. A qualitative study. The thesis examines young people, age 18-24, and their thoughts on drugs and alcohol. We examine their views on cannabis, alcohol, and heavy-end drugs. We examine their attitudes with focus on identity, normalization and social context. We come to the conclusion that the youth of today are in the process of normalizing drugs such as cannabis and ecstasy, and that they propagate their views further, onto other groups. We notice a distancing from alcohol, and a decreased use, but this use is in turn replaced by other substances. The youth of today use different substances for different occasions, why and what they use can be for many different reasons such as pain relief, stress relief, focusing, partying, relaxing, having fun with friends and for exploring their inner self. We examine their statements and reasoning, to try to understand their thoughts

Towards Machine Learning on data from Professional Cyclists

Professional sports are developing towards increasingly scientific training methods with increasing amounts of data being collected from laboratory tests, training sessions and competitions. In cycling, it is standard to equip bicycles with small computers recording data from sensors such as power-meters, in addition to heart-rate, speed, altitude etc. Recently, machine learning techniques have provided huge success in a wide variety of areas where large amounts of data (big data) is available. In this paper, we perform a pilot experiment on machine learning to model physical response in elite cyclists. As a first experiment, we show that it is possible to train a LSTM machine learning algorithm to predict the heart-rate response of a cyclist during a training session. This work is a promising first step towards developing more elaborate models based on big data and machine learning to capture performance aspects of athletes.Comment: Accepted for the 12th World Congress on Performance Analysis of Sports, Opatija, Croatia, 201