On the Role of Social Identity and Cohesion in Characterizing Online Social Communities

Two prevailing theories for explaining social group or community structure are cohesion and identity. The social cohesion approach posits that social groups arise out of an aggregation of individuals that have mutual interpersonal attraction as they share common characteristics. These characteristics can range from common interests to kinship ties and from social values to ethnic backgrounds. In contrast, the social identity approach posits that an individual is likely to join a group based on an intrinsic self-evaluation at a cognitive or perceptual level. In other words group members typically share an awareness of a common category membership. In this work we seek to understand the role of these two contrasting theories in explaining the behavior and stability of social communities in Twitter. A specific focal point of our work is to understand the role of these theories in disparate contexts ranging from disaster response to socio-political activism. We extract social identity and social cohesion features-of-interest for large scale datasets of five real-world events and examine the effectiveness of such features in capturing behavioral characteristics and the stability of groups. We also propose a novel measure of social group sustainability based on the divergence in group discussion. Our main findings are: 1) Sharing of social identities (especially physical location) among group members has a positive impact on group sustainability, 2) Structural cohesion (represented by high group density and low average shortest path length) is a strong indicator of group sustainability, and 3) Event characteristics play a role in shaping group sustainability, as social groups in transient events behave differently from groups in events that last longer

European Regional Development Policies: History and Current Issues

The objective of this paper is to demonstrate that the European regional development funds do not allow simultaneous achievement of goals of efficiency and equity when they are dedicated to financing transportation infrastructures. The paper first gives some insights on the history and the nature of regional development funds. Then we focus on the degree to which Ireland, Spain and Portugal (but not Greece), the main beneficiaries of regional policies, have been able to move to the European average (in terms of per capita income) since their membership in the EU, which also corresponds to the time when regional assistance was initiated in these countries. Empirical evidence also reveals that income disparities are increasing among regions within each of these countries and this raises the question as to whether the impact of regional funds is or is not rather favorable to this particular convergence pattern, given that one of the primary objectives of regional funding has been to ensure greater cohesion over the whole European territory. The answer comes mainly from the type of infrastructure regional funds finance. Since a significant part of regional funds is devoted to transportation issues, their impact on regional development has to be seen in the light of characteristics of the transport sector and the specific requirements in transport of each individual sector. The paper concludes that transportation infrastructures promote the country's aggregate growth but cannot be seen as an efficient instrument to reduce interregional disparities in Europe.published or submitted for publicatio

Urban Regeneration in a ‘City of Culture’ the Case of Pécs, Hungary

The development of Pécs is essentially due to its historically central location and to the fact that the regional institutions and the revenues generated by them have enriched the city. This functional wealth elevated the city to a position above the surrounding settlements. In its development, culture has always played a significant role. From the second half of the 19th century, it was industrial development which contributed most to its growth, a trend which was reversed at the end of the 20th century. The crisis arrived with the transition in the 1980s and has so far not been resolved. The city once more based its growth concept on human capital and on the cultural tradition when formulating new development strategy, and, as a result, it won the title of European Capital of Culture 2010. However, market processes and EU development funds necessarily generate trends which are rather more global, and in the post-socialist cities there are insufficient funds for endogenous development based on local factors to be realised

Evaluation of open pit slope stability using various slope angles and element types

Purpose. The objective of this study is to demonstrate a method to select the optimal slope angle related to three principal factors: safety, productivity and mining costs. Also, it aims to investigate the accuracy of numerical analysis using different element types and order. Methods. Series of two-dimensional elasto-plastic finite-element models has been constructed at various slope angles (e.g. 40°, 45°, 50°, 55°, 60°, 65°, and 70°) and different element types (e.g. 3-noded triangle (T3), 6-noded triangle (T6), 4-noded quadrilateral (Q4) and 8-noded quadrilateral (Q8).The results are presented, discussed and compared at various slope angles and element types in terms of critical strength reduction factor (CSRF) or its equivalent factor of safety (FOS), total rock slope displacement, mine production and mining costs. Findings. The results reveal that, the mine productivity increases as slope angle increases, however, slope stability deteriorates. Alternatively, the factor of safety (FOS) decreases as slope angle becomes steeper (e.g. minimum factor of safety is obtained at highest steep angle of 70°). Despite of the increasing in computation time, the analysis shows that, the accuracy of the modelling increases when adopting high-order element types (e.g. 8-noded quadrilateral and 6-noded triangle elements). Originality. This study provides a methodology for the application of the numerical modelling methods on open pit mine. As a result, the mine planners will be able to know ahead of time the optimal slope angle with respect to safety, production and mining costs. Practical implications. This study sheds light on the usefulness of adopting numerical modelling analysis in the feasibility studies to determine and compare mining costs against safety and slope angle.Мета. Розробка методики для підбору оптимального кута нахилу борта кар’єру з видобутку мідно-нікелевих руд з урахуванням трьох головних чинників: безпека, продуктивність та витрати, а також перевірка точності чисельного аналізу при використанні елементів різного типу і порядку. Методика. Побудовано серії двовимірних пружно-пластичних кінцево-елементних моделей (КЕМ) для різних кутів нахилу борта кар’єру (наприклад, 40°, 45°, 50°, 55°, 60°, 65° і 70°) та з елементами різного типу (3-вузловий трикутник (T3), 6-вузловий трикутник (T6), 4-вузловий чотирикутник (Q4) і 8-вузловий чотирикутник (Q8)). Чисельне моделювання виконано у програмному продукті Rock and Soil 2-Dimensional Analysis Program. В якості критерію руйнування прийнято критерій міцності Кулона-Мора. Результати. Дослідження показали, що продуктивність шахти зростає зі збільшенням кута нахилу борта кар’єру; однак при цьому зменшується його стійкість, і навпаки, чим крутіше кут нахилу борта, тим менше коефіцієнт безпеки. Так, мінімальному значенню коефіцієнта безпеки відповідає найбільший кут нахилу 70°. Незважаючи на більш тривалі обчислення, аналіз показав, що точність моделювання зростає при використанні елементів високого порядку (8-вузлового чотирикутника і 6-вузлового трикутника). Наукова новизна. Розроблено новий методичний підхід для застосування чисельного моделювання для оцінки стійкості бортів кар’єрів з точки зору граничного коефіцієнта зниження міцності або його еквівалентного коефіцієнта безпеки, загального зсуву схилів, продуктивності та витрат на видобуток. Практична значимість. Дослідження доводять ефективність застосування чисельного моделювання для визначення доцільності витрат при різних кутах нахилу борта для забезпечення безпеки робіт. В результаті його застосування проектувальники кар’єрів зможуть заздалегідь спланувати оптимальний кут нахилу борта з урахуванням безпеки, продуктивності і витрат.Цель. Разработка методики для подбора оптимального угла наклона борта карьера по добыче медно-никелевых руд с учетом трех главных факторов: безопасность, производительность и затраты, а также проверка точности численного анализа при использовании элементов различного типа и порядка. Методика. Построены серии двумерных упругопластических конечно-элементных моделей (КЭМ) для разных углов наклона борта карьера (например, 40°, 45°, 50°, 55°, 60°, 65° и 70°) и с элементами разного типа (3-узловой треугольник (T3), 6-узловой треугольник (T6), 4-узловой четырехугольник (Q4) и 8-узловой четырехугольник (Q8)). Численное моделирование выполнено в программном продукте Rock and Soil 2-Dimensional Analysis Program. В качестве критерия разрушения принят критерий прочности Кулона-Мора. Результаты. Исследования показали, что производительность шахты растет с увеличением угла наклона борта карьера, однако при этом уменьшается его устойчивость, и наоборот, чем круче угол наклона борта, тем меньше коэффициент безопасности. Так, минимальному значению коэффициента безопасности соответствует самый большой угол наклона 70°. Несмотря на более длительные вычисления, анализ показал, что точность моделирования возрастает при использовании элементов высокого порядка (8-узлового четырехугольника и 6-узлового треугольника). Научная новизна. Разработан новый методический подход для применения численного моделирования для оценки устойчивости бортов карьеров с точки зрения предельного коэффициента снижения прочности или его эквивалентного коэффициента безопасности, общего смещения склонов, производительности и затрат на добычу. Практическая значимость. Исследования доказывают эффективность применения численного моделирования для определения целесообразности затрат при различных углах наклона борта для обеспечения безопасности работ. В результате его применения проектировщики шахт смогут заранее спланировать оптимальный угол наклона борта с учетом безопасности, производительности и затрат.The authors acknowledge the support of Rocscience Inc. for getting a free two-week full-version of RS2D (Rock-Soil two-dimensional finite-element analysis program). The authors are grateful for their support

Influence of cutting sequence and time effects on cutters and roof falls in underground coal mine -- numerical approach

Roof falls are among the most serious safety hazards faced by underground coal mines worldwide. Due to the stringent safety measures and development of the innovative support systems in the past few decades, their numbers were drastically reduced but have not been eliminated. Underground observations reveal that a number of larger roof falls are preceded by the development of shear failures near pillar ribs, termed cutters or guttering. In the past, many factors were identified as responsible for the development of cutters and ultimately roof falls. These factors can be broadly classified as stress related and non stress related. Although some useful work on the stress related aspects was conducted in the past, in this dissertation the cutter instability is investigated in more details while including some finer aspects of the mining process in particular the cutting sequence, which were not given due consideration before.;Three dimensional finite difference modeling has been carried out to accomplish the research objectives in this dissertation. The strain softening material behavior with cutting sequence has been used to realistically simulate the cutter formation as suggested by Gadde and Peng, 2005. A few cutting sequences employed by some U.S. coal mines have been considered in this study. This was done to understand if the cutting sequence has any significant influence over cutter formation. Apart from cutting sequence, factors such as the cut length, step cutting and the turning direction of crosscut into and away from major and minor horizontal stress are also examined for their effect on cutter development. Further, in contrast to past work, the effect of change in the immediate roof rock properties and horizontal stress directions are studied in several multiple entry models while simulating some realistic cutting sequences.;Field observations show that some cutters develop after a significant amount of time is elapsed since the area has been mined. While such time-dependent effects could be simulated with numerical modeling by using appropriate creep laws, due to the lack of knowledge on creep properties of coal measures rocks, realistic analysis is difficult at this stage. However, to consider the time effect on development of roof instability, a simple methodology has been suggested in this dissertation. The effect of different parameters like, entry and pillar width, intersection geometry has been correlated with the standup time for the observed roof falls at an IL Basin coal mine.;The combination of weak immediate roof and high horizontal stresses could have a devastating effect on roof stability. It\u27s very difficult to completely avoid roof instability in such conditions. In this research, based on the understanding of cutter development and roof falls, a few simple and practicable recommendations are made to minimize such instabilities. While these suggestions may not completely eliminate the roof failures, they may enhance the standup time to levels that will allow safer extraction of the reserve

When Big Isn’t Better: Why Smaller International Initial Public Offering Firms Seem to Win

There is a considerable amount of research suggesting that “being international” is better. While that may be the case, the assumption remains tenuous at best, and research that considers organizational size provides results contesting this assumption. In particular, we explore the effect of having international sales and operations on both long and short-term performance of initial public offering (IPO) firms. We also explore the “size” phenomenon evident in prior research that suggests smaller firms seem to perform better when they are international than do medium size firms. By applying work from the field of human resource management, we suggest that the ‘size’ phenomenon may be related to the level of structural cohesion in the organization. Our longitudinal study supports the hypothesis that international companies with higher levels of structural cohesion are more successful