A Study of Multicast Performance in IEEE 802.11 Wireless Local Area Networks

Langattomat lähiverkot ovat yleistyneet ja monin paikoin niillä pyritään täysin korvaamaan perinteiset kaapeloidut verkot. Samalla verkoissa välitettävät palvelut monipuolistuvat. Etenkin interaktiivisten sisältöjen ja viiveriippuvaisten palvelujen välittämisessä korostuvat verkolle asettavat vaatimukset suorituskyvystä ja palveluntasosta. Radiotaajuuksilla tapahtuva tiedonsiirto on ongelmallista siirtomedian jaetun luonteen vuoksi. Käytettäessä ympärisäteileviä antenneja jokainen kantomatkan päässä oleva asema kuulee lähetyksen, vaikkei se olisi sille suunnattu. Tämä luo turvallisuusongelman, mutta lisäksi heikentää tehokkuutta, koska nykyisellä antenniteknologialla vain yksi asema kerrallaan voi lähettää häiriöttä kantoalueellaan. Täsmälähetykset yhden lähteen ja useiden kohteiden välillä luovat erillisiä siirtolinkkejä. Olisi luontevampaa luoda yksi lähetysvirta, johon useat vastaanottajat voivat kytkeytyä. Kaistan säästön vastapainona on tarve luoda ja ylläpitää näitä yhteyksiä. Käyttäjien liikkuvuuden ja siirtotien vaihtelevien ominaisuuksien vuoksi langattoman verkon rakenne ja rajat ovat epäselviä. Näihin haasteisiin on vastattava sekä protokolla- että sovellustasolla. Tässä tutkielmassa käydään ensin läpi IEEE 802.11 -standardin mukaisen langattoman verkon perusteet ja sen ominaisuuksiin liittyvät tyypilliset ongelmakohdat. Yleis- ja ryhmälähetyksiä tarkastellaan ensin perinteisessä IEEE 802.3 standardin mukaisessa langallisessa lähiverkossa ja selvitetään, miten vastaavat ominaisuudet toteutuvat IEEE 802.11 standardien mukaisissa langattomissa verkoissa. Käyttötapaustutkimuksissa keskitytään rajatussa ympäristössä tapahtuviin ryhmälähetyksiin. Erityisesti tutkitaan langattomien ryhmälähetysten käyttökelpoisuutta sekä langattoman ympäristön asettamia erityisvaatimuksia.

Helsinki hub – new traffic flows and business networks

This thesis is the Logistics Development Forum's assignment and the work dealing with the development of the Port of Helsinki as part of Helsinki hub. The Forum aims to develop logistics efficiency through public-private co-operation and development of the port is clearly dependent on both factors. Freight volumes in the Port of Helsinki are the biggest single factor in hub and, therefore, the role of the port of the entire hub development is strong. The aim is to look at how the port will develop as a result of changes in the foreign trade of Finland and the Northern European logistics trends in 25 years time period. Work includes the current state analysis and scenario work. The analyses are intended to find out, which trends are the most important in the port volume development. The change and effect of trends is examined through scenarios based on current state. Based on the work, the structure of Finnish export industry and international demand are in the key role in the port volume development. There is significant difference between demands of Finnish exporting products in different export markets and the development between the markets has different impacts on the port volumes by mass and cargo type. On the other hand, the Finnish economy is stuck in a prolonged recession and competition between ports has become a significant factor in the individual port's volume development. Ecological valuesand regulations have changed the competitive landscape and maritime transport emissions reductions has become an important competitive factor for short routes in the Baltic Sea, such as in the link between Helsinki and Tallinn.

Relay protection in active distribution networks

Increasingly growing share of distributed generation in the whole electrical power system’s generating system is currently a worldwide tendency, driven by several factors, encircling mainly difficulties in refinement of megalopolises’ distribution networks and its maintenance; widening environmental concerns adding to both energy efficiency approaches and installation of renewable sources based generation, inherently distributed; increased power quality and reliability needs; progress in IT field, making implementable harmonization of needs and interests of different-energy-type generators and consumers. At this stage, the volume, formed by system-interconnected distributed generation facilities, have reached the level of causing broad impact toward system operation under emergency and post-emergency conditions in several EU countries, thus previously implementable approach of their preliminary tripping in case of a fault, preventing generating equipment damage and disoperation of relay protection and automation, is not applicable any more. Adding to the preceding, withstand capability and transient electromechanical stability of generating technologies, interconnecting in proximity of load nodes, enhanced significantly since the moment Low Voltage Ride-Through regulations, followed by techniques, were introduced in Grid Codes. Both aspects leads to relay protection and auto-reclosing operation in presence of distributed generation generally connected after grid planning and construction phases. This paper proposes solutions to the emerging need to ensure correct operation of the equipment in question with least possible grid refinements, distinctively for every type of distributed generation technology achieved its technical maturity to date and network’s protection. New generating technologies are equivalented from the perspective of representation in calculation of initial steady-state short-circuit current used to dimension current-sensing relay protection, and widely adopted short-circuit calculation practices, as IEC 60909 and VDE 0102. The phenomenon of unintentional islanding, influencing auto-reclosing, is addressed, and protection schemes used to eliminate an sustained island are listed and characterized by reliability and implementation related factors, whereas also forming a crucial aspect of realization of the proposed protection operation relieving measures.

Benefits of a low-cost one-phase current distortion detection device in appliance supply in low-voltage residential networks

In this bachelor’s thesis are examined the benefits of current distortion detection device application in customer premises low voltage networks. The purpose of this study was to find out if there are benefits for measuring current distortion in low-voltage residential networks. Concluding into who can benefit from measuring the power quality. The research focuses on benefits based on the standardization in Europe and United States of America. In this research, were also given examples of appliances in which current distortion detection device could be used. Along with possible illustration of user interface for the device. The research was conducted as an analysis of the benefits of current distortion detection device in residential low voltage networks. The research was based on literature review. The study was divided to three sections. The first explain the reasons for benefitting from usage of the device and the second portrays the low-cost device, which could detect one-phase current distortion, in theory. The last section discuss of the benefits of usage of current distortion detection device while focusing on the beneficiaries. Based on the result of this research, there are benefits from usage to the current distortion detection device. The main benefitting party of the current distortion detection device was found to be manufactures, as they are held responsible of limiting the current distortion on behalf of consumers. Manufactures could adjust equipment to respond better to the distortion by having access to on-going current distortion in network. The other benefitting party are system operators, who would better locate distortion issues in low-voltage residential network to start prevention of long-term problems caused by current distortion early on.

Pretraining Convolutional Neural Networks for Visual Recognition

Convolutional Neural Networks (CNN) have become the state-of-the-art methods on many large scale visual recognition tasks. For a lot of practical applications, CNN architectures have a restrictive requirement: A huge amount of labeled data are needed for training. The idea of generative pretraining is to obtain initial weights of the network by training the network in a completely unsupervised way and then fine-tune the weights for the task at hand using supervised learning. In this thesis, a general introduction to Deep Neural Networks and algorithms are given and these methods are applied to classification tasks of handwritten digits and natural images for developing unsupervised feature learning. The goal of this thesis is to find out if the effect of pretraining is damped by recent practical advances in optimization and regularization of CNN. The experimental results show that pretraining is still a substantial regularizer, however, not a necessary step in training Convolutional Neural Networks with rectified activations. On handwritten digits, the proposed pretraining model achieved a classification accuracy comparable to the state-of-the-art methods.

The role of diaspora networks in opportunity exploitation by ethnic entrepreneurs in Finland

The thesis explores the role of diaspora network in opportunity exploitation by ethnic entrepreneurs in Finland. The purpose of this study is to how ethnic entrepreneurs in Finland can exploit diaspora networks and how significant support of these networks in comparison with governmental and other official institutional support. Increased mobility of the global population and number of immigrants all around the world contribute into interest of academics to this topic. At the same time, in comparison with other European countries for Finland this phenomenon is new. However, increasing number of immigrants add to academic interest to this topic. The theoretical background of this thesis consists of the collection of studies done on diaspora networks and ethnic entrepreneurs as internationally as in Finland. The concept of cooperation between diaspora and ethnic entrepreneurs describes how diaspora can support ethnic entrepreneur and emphasize importance of diaspora ties for business. At the end of the theoretical section theoretical a special grid was proposed as summary of the academic literature review. The empirical research for this study is based on the interviews with five ethnic entrepreneurs in Finland. Empirical data was analyzed and compared with the similar studies done internationally. During the interviews analyses were stressed aspects of the significance of governmental and other official institutional support. During the interviews analyses were stressed aspects of the significance of the governmental and other official institutional support. According to the main findings diaspora can play positive and in some cases crucial role in the business of ethnic entrepreneurs in Finland. Moreover, diaspora can be a facilitator of internationalization of ethnic entrepreneurs. At the same time, there are several factors which might increase or decrease role of diaspora. The ways of the utilization of diaspora network were combined in the empirical grid. The study enhance understanding of the challenges of ethnic entrepreneurs and provides certain recommendations for the policy makers, ethnic entrepreneurs and managers of official institutions involved in cooperation with ethnic entrepreneurs

The Role Of Social Networks In New Venture Internationalization: Case Of Russian And Finnish Firms

The purpose of current master thesis research is to investigate the role of social networks in internationalization of Russian and Finnish firms. Literature review of existing empirical researches on the topic is conducted in order to identify the gap, which is fulfilled by empirical research of 4 Russian and 1 Finnish firm that have established international operations no later than 8 years since their foundation. In-depth semi-structured interviews have shown that business network has been an influencing factor in firms’ internationalization and that even if social network is not the driver of internationalization, it becomes important when a company has established international presence and is working on its enlargement. The study has both theoretical and practical contribution by contributing to research of Russian and Finnish firms’ internationalization and by showing examples of successful foreign market entry of companies from different industries. General practical implication of current thesis is that it shows the efficient ways of entrepreneurs’ social network usage in business development in international scope.

Managing Finnish-Russian Business Relationships and Networks During Conflicts

This thesis examines management of business relationships during conflicts. The context of this study is the international political conflict which started in 2013 and is still affecting international trade relations in 2016. More specifically, this study researches the effects of the conflict in Finnish-Russian trade. The research aim is to identify the implications of a political conflict in the Finnish-Russian business relationships and networks. Furthermore, the study will explore how does a company adapt or overcome the challenges and barriers posed by the international business environment. This research combines relevant theories in management of business relationships and networks in order to review the research data through a critical research frame. The theoretical frameworks are different structures of business relationship development processes, various stages of interaction, and characteristics and functions of business relationships. Moreover, this study will examine the effect of interdependency, commitment and trust in trade relations. Also, what are the important exchange processes and how do these processes affect business relationship and overall performance of joint business operations. Qualitative single case study method was used in this research. Case company was a Finnish multinational company. To understand the changes, the data was collected and analysed through process research approach by pattern-matching and drawing temporal bracketing over two different periods of time, first period in years 2011-2013 and second period in years 2014-2016. Empirical data was collected through a semi-structured interview and additional data was collected from internal and external secondary data sources. The findings of the study confirmed the relationship between trade and conflict. However, the effects are not significant for a company in grocery retail industry which has had earlier experience in Russia and has managed its business relationships and operations effectively. Macroeconomic factors affect companies operating in foreign dynamic markets and in order to sustain changes and to adapt, companies should invest in their business relationships. Trust-based relationships and a higher level of commitment allow companies to have more efficient and beneficial outcomes before and during uncertainty. Furthermore, well-maintained and coordinated business relationships provide the ability to adapt and overcome challenges during uncertainty. Such relationships have information, financial and social exchange processes which allow the partnering firms to have successful business relationship management in dynamic market environments.

On the edge : exploring homeless women's social networks

This thesis aims to uncover the ways that previously homeless women in the Niagara region are able (or unable) to rely on friends, family and service providers in times of crisis (homelessness and poverty). Eleven women were interviewed and their experiences indicate that social networks cannot take the place of comprehensive and inclusive social policy. Time and time again, their stories showed that they were left negotiating the detritus of neo-liberal policies.

Diatoms as indicators of lake trophic status

Relationships between surface sediment diatom assemblages and lake trophic status were studied in 50 Canadian Precambrian Shield lakes in the Muskoka-Haliburton and southern Ontario regions. The purpose of this study was to develop mathematical regression models to infer lake trophic status from diatom assemblage data. To achieve this goal, however, additional investigations dealing with the evaluation of lake trophic status and the autecological features of key diatom species were carried out. Because a unifying index and classification for lake trophic status was not available, a new multiple index was developed in this study, by the computation of the physical, chemical and biological data from 85 south Ontario lakes. By using the new trophic parameter, the lake trophic level (TL) was determined: TL = 1.37 In[1 +(TP x Chl-a / SD)], where, TP=total phosphorus, Chl-a=chlorophyll-a and SD=Secchi depth. The boundaries between 7 lake trophic categories (Ultra-oligotrophic lakes: 0-0.24; Oligotrophic lakes: 0.241-1.8; Oligomesotrophic lakes: 1.813.0; Mesotrophic lakes: 3.01-4.20; Mesoeutrophic lakes: 4.21-5.4; Eutrophic lakes: 5.41-10 and Hyper-eutrophic lakes: above 10) were established. The new trophic parameter was more convenient for management of water quality, communication to the public and comparison with other lake trophic status indices than many of the previously published indices because the TL index attempts to Increase understanding of the characteristics of lakes and their comprehensive trophic states. It is more reasonable and clear for a unifying determination of true trophic states of lakes. Diatom specIes autecology analysis was central to this thesis. However, the autecological relationship of diatom species and lake trophic status had not previously been well documented. Based on the investigation of the diatom composition and variety of species abundance in 30 study lakes, the distribution optima of diatom species were determined. These determinations were based on a quantitative method called "weighted average" (Charles 1985). On this basis, the diatom species were classified into five trophic categories (oligotrophic, oligomesotrophic, mesotrophic, mesoeutrophic and eutrophic species groups). The resulting diatom trophic status autecological features were used in the regressIon analysis between diatom assemblages and lake trophic status. When the TL trophic level values of the 30 lakes were regressed against their fi ve corresponding diatom trophic groups, the two mathematical equations for expressing the assumed linear relationship between the diatom assemblages composition were determined by (1) uSIng a single regression technique: Trophic level of lake (TL) = 2.643 - 7.575 log (Index D) (r = 0.88 r2 = 0.77 P = 0.0001; n = 30) Where, Index D = (0% + OM% + M%)/(E% + ME% + M%); 4 (2) uSIng a' multiple regressIon technique: TL=4.285-0.076 0%- 0.055 OM% - 0.026 M% + 0.033 ME% + 0.065 E% (r=0.89, r2=0.792, P=O.OOOl, n=30) There was a significant correlation between measured and diatom inferred trophic levels both by single and multiple regressIon methods (P < 0.0001, n=20), when both models were applied to another 20 test lakes. Their correlation coefficients (r2 ) were also statistically significant (r2 >0.68, n=20). As such, the two transfer function models between diatoms and lake trophic status were validated. The two models obtained as noted above were developed using one group of lakes and then tested using an entirely different group of lakes. This study indicated that diatom assemblages are sensitive to lake trophic status. As indicators of lake trophic status, diatoms are especially useful in situations where no local trophic information is available and in studies of the paleotrophic history of lakes. Diatom autecological information was used to develop a theory assessing water quality and lake trophic status.

Niagara alternative food projects : networks, discourses and nature /

This thesis undertakes an exploration of the nature of alternative food projects in Niagara. A review of various theoretical approaches to the study of food and agriculture, suggests that actor-network theory offers the most useful lens through which to understand these projects. In particular, actor-network theory facilitates non-dualistic theorisations of power and scale and a commitment to the inclusion of non-humans in the 'social' sciences. The research is based on 19 in-depth interviews with actors involved in various urban and rural projects including community supported agriculture, community gardens, chefs using local seasonal food, a winery that grows organically, the good food box, a value-added small business, and organic producers. The analysis consists of four themes. The first analytical section pays special attention to the prominence of agri-tourism in Niagara, and examines the ways in which the projects in the sample interact with agri-tourist networks. In the second section the discussion focuses on the discourses and practices of resistance among Niagara alternative food actors. The participants' interviews suggest there are more discourses of resistance toward agri-tourist than toward dominant food networks. The third section questions commodity chain theorisations of alternative food projects. In particular, this section shows how the inclusion of non-human actors in an analysis confounds conceptualisations of 'short' and 'local' chains. The final analytical section assesses relations of power in Niagara alternative food projects. Three important conclusions arise from this research. First, Niagara alternative food projects cannot be conceptualised as operating at the 'local' scale. Broadening the scope of analysis to include non-human actors, it becomes apparent that these projects actually draw on a variety of extra-local actors. They are at once local and global. Second, the projects in this sample are simultaneously part of alternative, dominant and agri-tourist networks. While Niagara alternative food projects do perform many of the roles characteristic of alternative food systems, they are also involved in practices of development, business, and class distinction. Thus, alternative food networks should not be understood as separate from and in direct opposition to dominant food networks. Despite the second conclusion, this research determines that Niagara alternative food projects have made significant strides in the reworking of power. The projects represented in this thesis do engage in resistant practices and are associated with increased levels ofjustice.

'What ever happened to breakdancing?' : transnational b-boy/b-girl networks, underground video magazines and imagined affinities

In 1997, Paul Gilroy was able to write: "I have been asking myself, whatever happened to breakdancing" (21), a form of vernacular dance associated with urban youth that emerged in the 1970s. However, in the last decade, breakdancing has experienced a massive renaissance in movies (You Got Served), commercials ("Gotta Have My Pops!") and documentaries (the acclaimed Freshest Kids). In this thesis, 1 explore the historical development of global b-boy/bgirl culture through a qualitative study involving dancers and their modes of communication. Widespread circulation of breakdancing images peaked in the mid-1980s, and subsequently b-boy/b-girl culture largely disappeared from the mediated landscape. The dance did not reemerge into the mainstream of North American popular culture until the late 1990s. 1 argue that the development of major transnational networks between b-boys and b-girls during the 1990s was a key factor in the return of 'b-boying/b-girling' (known formerly as breakdancing). Street dancers toured, traveled and competed internationally throughout this decade. They also began to create 'underground' video documentaries and travel video 'magazines.' These video artefacts circulated extensively around the globe through alternative distribution channels (including the backpacks of traveling dancers). 1 argue that underground video artefacts helped to produce 'imagined affinities' between dancers in various nations. Imagined affinities are identifications expressed by a cultural producer who shares an embodied activity with other practitioners through either mediated texts or travels through new places. These 'imagined affinities' helped to sustain b-boy/b-girl culture by generating visual/audio representations of popularity for the dance movement across geographical regions.

Particle swarm optimization for two-connected networks with bounded rings

The Two-Connected Network with Bounded Ring (2CNBR) problem is a network design problem addressing the connection of servers to create a survivable network with limited redirections in the event of failures. Particle Swarm Optimization (PSO) is a stochastic population-based optimization technique modeled on the social behaviour of flocking birds or schooling fish. This thesis applies PSO to the 2CNBR problem. As PSO is originally designed to handle a continuous solution space, modification of the algorithm was necessary in order to adapt it for such a highly constrained discrete combinatorial optimization problem. Presented are an indirect transcription scheme for applying PSO to such discrete optimization problems and an oscillating mechanism for averting stagnation.

Scales, networks and uncertainty : an examination of environmental policy-making in Ontario

Through a case-study analysis of Ontario's ethanol policy, this thesis addresses a number of themes that are consequential to policy and policy-making: spatiality, democracy and uncertainty. First, I address the 'spatial debate' in Geography pertaining to the relevance and affordances of a 'scalar' versus a 'flat' ontoepistemology. I argue that policy is guided by prior arrangements, but is by no means inevitable or predetermined. As such, scale and network are pragmatic geographical concepts that can effectively address the issue of the spatiality of policy and policy-making. Second, I discuss the democratic nature of policy-making in Ontario through an examination of the spaces of engagement that facilitate deliberative democracy. I analyze to what extent these spaces fit into Ontario's environmental policy-making process, and to what extent they were used by various stakeholders. Last, I take seriously the fact that uncertainty and unavoidable injustice are central to policy, and examine the ways in which this uncertainty shaped the specifics of Ontario's ethanol policy. Ultimately, this thesis is an exercise in understanding sub-national environmental policy-making in Canada, with an emphasis on how policy-makers tackle the issues they are faced with in the context of environmental change, political-economic integration, local priorities, individual goals, and irreducible uncertainty.

Automatic Inference of Graph Models for Complex Networks with Genetic Programming

Complex networks can arise naturally and spontaneously from all things that act as a part of a larger system. From the patterns of socialization between people to the way biological systems organize themselves, complex networks are ubiquitous, but are currently poorly understood. A number of algorithms, designed by humans, have been proposed to describe the organizational behaviour of real-world networks. Consequently, breakthroughs in genetics, medicine, epidemiology, neuroscience, telecommunications and the social sciences have recently resulted. The algorithms, called graph models, represent significant human effort. Deriving accurate graph models is non-trivial, time-intensive, challenging and may only yield useful results for very specific phenomena. An automated approach can greatly reduce the human effort required and if effective, provide a valuable tool for understanding the large decentralized systems of interrelated things around us. To the best of the author's knowledge this thesis proposes the first method for the automatic inference of graph models for complex networks with varied properties, with and without community structure. Furthermore, to the best of the author's knowledge it is the first application of genetic programming for the automatic inference of graph models. The system and methodology was tested against benchmark data, and was shown to be capable of reproducing close approximations to well-known algorithms designed by humans. Furthermore, when used to infer a model for real biological data the resulting model was more representative than models currently used in the literature.