Theoretical and experimental study of a pendulum excited by random loads

2018 ◽  
Vol 30 (5) ◽  
pp. 912-927 ◽  
Author(s):  
L. DOSTAL ◽  
M.-A. PICK

Results on the behaviour of a pendulum which is parametrically excited by large amplitude random loads at its pivot are presented, including a novel experimental case study. Thereby, it is dealt with a random excitation by a non-white Gaussian stochastic process with prescribed spectral density. Special focus is devoted to stochastic processes resulting from random sea wave elevation and the question whether random sea waves can lead to rotational motion of the parametrically excited pendulum. The motivation for such an experimental study is energy harvesting from ocean waves.

2021 ◽  
Vol 9 (4) ◽  
pp. 422
Author(s):  
Alessio Innocenti ◽  
Miguel Onorato ◽  
Carlo Brandini

Extreme sea waves, although rare, can be notably dangerous when associated with energetic sea states and can generate risks for the navigation. In the last few years, they have been the object of extensive research from the scientific community that helped with understanding the main physical aspects; however, the estimate of extreme waves probability in operational forecasts is still debated. In this study, we analyzed a number of sea-states that occurred in a precise area of the Mediterranean sea, near the location of a reported accident, with the objective of relating the probability of extreme events with different sea state conditions. For this purpose, we performed phase-resolving simulations of wave spectra obtained from a WaveWatch III hindcast, using a Higher Order Spectral Method. We produced statistics of the sea-surface elevation field, calculating crest distributions and the probability of extreme events from the analysis of a long time-series of the surface elevation. We found a good matching between the distributions of the numerically simulated field and theory, namely Tayfun second- and third- order ones, in contrast with a significant underestimate given by the Rayleigh distribution. We then related spectral quantities like angular spreading and wave steepness to the probability of occurrence of extreme events finding an enhanced probability for high mean steepness seas and narrow spectra, in accordance with literature results, finding also that the case study of the reported accident was not amongst the most dangerous. Finally, we related the skewness and kurtosis of the surface elevation to the wave steepness to explain the discrepancy between theoretical and numerical distributions.


Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 699
Author(s):  
Ruifeng Wang ◽  
Xiong Wu ◽  
Yanliang Zhai ◽  
Yuxuan Su ◽  
Chenhui Liu

Chengde City boasts a wealth of high-quality mineral water resources characterized by a high level of strontium (Sr), a low level of sodium, and low alkalinity. In order to study the mechanism of formation of Sr-bearing mineral water in Chengde and to scientifically guide future mineral water exploration, taking three typical mineral water exploration areas in Chengde as examples, this paper studies the sources of Sr in mineral water and the general rules of its dissolution via a laboratory static leaching experiment and impact experiments, and it provides an analysis of the characteristics of typical rock samples. The research results indicate that the content of Sr in surrounding rock and the characteristics of minerals existing in surrounding rock jointly control the dissolution of Sr in water; that CO2 can promote the formation of mineral water containing Sr; and that temperature increases may boost the dissolution of Sr from carbonate minerals but also inhibit the dissolution of Sr from silicate minerals.


Author(s):  
Malte Zimmermann

The chapter provides a general overview of the formal marking of pluractionality in Chadic languages and its observable interpretive effects, with a special focus of Hausa. Section 29.2 introduces the three major strategies for marking pluractionality in Chadic (reduplication, infixing/ablauting, suffixation), before discussing possible correspondences between formal marking and interpretation. The empirical focus lies on languages that do not figure prominently in earlier works on pluractionality in Chadic. The section also contains a case study on the interpretation of different ways of pluractional marking in West Chadic Bole. Section 29.3 introduces the basic patterns of pluractional marking in Hausa, and their basic semantic interpretation in terms of distribution over participants or places. It then discusses secondary, pragmatically inferred meaning effects in terms of abundance, individuation, or intensification. The chapter ends with a discussion of why pluractional marking in Hausa does not easily allow for iterative event interpretations.


2021 ◽  
Vol 19 (3) ◽  
pp. 57-76
Author(s):  
Katarzyna Dośpiał-Borysiak

The aim of this article is to discuss urban climate policies, with a special focus on Helsinki, the fast growing capital of Finland. The preconditionfor the study is that metropolitan areas in Finland hold a central place fornational climate policies due to their population and economic impact. Thecase study proves that the city, which had disadvantageous conditions for climatesolutions in the early 90’s, has successfully remodelled its approach andpresently joins the group of world cities declaring carbon neutrality in comingyears. The change was possible due to a favourable political climate, a multistakeholderand inclusive approach, public involvement, and the correlationbetween public and private initiatives. The study is based on statistical data,institutional analysis, and a comparison of the strategic documents of the cityof Helsinki in the area of climate planning.


2017 ◽  
pp. 1-9 ◽  
Author(s):  
Ivana Šimonová ◽  
Blanka Klímová ◽  
Petra Poulová ◽  
Pavel Pražák
Keyword(s):  

2020 ◽  
Vol 25 (2) ◽  
pp. 379-393
Author(s):  
Shivani Ekkanath

The postcolonial narratives we see today are a study in contrast and tell a different tale from their colonial predecessors as minorities and individuals finally have found the voice and position to tell their stories. Histories written about our culture and societies have now found a new purpose and voice. The stories we have passed down from generation to generation through both oral and written histories, continue to morph and change with the tide of time as they re-centre our cultural narratives and shared experiences. As a result, the study of diaspora and transnationalism have altered the way in which we view identity in different forms of multimedia and literature. In this paper, the primary question which will be examined is, how and to what extent does Indian post-colonial literature figure in the formation of identity in contemporary art and literature in the context of ongoing postcolonial ideas and currents? by means of famous and notable postcolonial literary works and theories of Indian authors and theoreticians, with a special focus on the question and notion of identity. This paper works on drawing parallels between themes in Indian and African postcolonial literary works, especially themes such as power, hegemony, east meets west, among others. In this paper, European transnationalism will also be analysed as a case study to better understand postcolonialism in different contexts. The paper will seek to explore some of the gaps in the study of diasporic identity and postcolonial studies and explore some of the changes and key milestones in the evolution of the discourse over the decades.


2013 ◽  
Vol 2 (4) ◽  
pp. 19
Author(s):  
Jenny Calabrese ◽  
Cesare Pacini ◽  
Concetta Vazzana ◽  
Mariana Nikolla

Dependence of conventional agricultural systems on chemical fertilizers and pesticidesmakes agricultural systems less stable and important drift polluters influencing to theregional and global sustainability. This problem made human being think about thealternative systems: agricultural systems that mimic natural systems and are friendly to theenvironment; those have higher economical efficiency concerning production level andcosts. The objective of the present study was sustainability assessment and comparison oforganic and conventional system with special focus environmental and economicalperformance. The case study consisted of two organic and conventional olive producingfarms in the South of Italy. The method used for sustainability assessment wasEnvironmental Accounting Information System (EAIS) that integrates togetherenvironmental (soil organic matter, soil erosion, genetic and landscape biodiversity,EPRIP, etc ) and economical indicators (gross margin). Data used for assessment ofEAIS indicators values were mainly collected from: farm economic-accounting systems,interviews, farm maps, area public organizations, bibliographical sources, farm nutrientaccounting systems, observations and field assessments and chemical soil analyses. Theindicator values measured into two farms were compared to theoretical or referenceindicator values. Based on indicator assessment it was concluded that organic olivegrowing farm had better performance than conventional farm.


2021 ◽  
Vol 11 (2) ◽  
pp. 73-85
Author(s):  
Suada A. Dzogovic ◽  
◽  
Vehbi Miftari ◽  

The topic of this article presents communication challenges and the role of the media in constructing an image of migrants and refugees as “the others” in our societies today. The article analyses the migrant situation in South-Eastern Europe, specifically in migration crisis in Bosnia and Herzegovina that has been going on since 2018. The aim is to present the basic aspects of this issue and offer answers to key questions - who are migrants and refugees, what’s their own identity, from which countries do they come, how do they cross the border, where do they go, what is the state’s attitude towards them, what forms and channels of communication the state and other stakeholders use toward them, who cares for them, what do they preserve from their national, cultural and/or language identities and how do they construct self-identity and confront with the “hosting identities”, who donates funds for migration management and how they are managed? Also, a special focus of the research will be on the human rights of migrants and refugees in Bosnia and Herzegovina, which is the subject of various discussions - both within the country itself and among various humanitarian, governmental and non-governmental international organizations in the EU and beyond.


2019 ◽  
pp. 203-220 ◽  
Author(s):  
Marzena Anna Maciulewicz

Newcomers and Locals. Invisible Boundaries Among Inhabitants of the Divided City in the BalkansResearch on divided cities in the Balkans focuses mostly on ethnic/national divisions. Is this perspective, however, truly viable and sufficient for the description of post-conflict cities in the Balkans? The question is posed not only because of the fact that every city is somehow divided or fragmented. More noteworthy, and not widely known, is the fact that the unstable structure of a city’s population is much more complex with its intergroup relations becoming much more complicated – a fact commonly disregarded due to the importance assigned to ethnic/national rifts which have dominated the narrative of the divided city. Underestimating the importance of other relations within society and the dynamics of a highly changeable social structure, one cannot uncover the actual nature of intergroup relations in a divided city.The main objective of this paper is to briefly present the state of contemporary inter- and intragroup relations in a divided city, with a special focus on inhabitants’ residential status. The article is based mainly on the case study of Mitrovica supplemented with references to other cities in the Balkans considered as divided. The paper is based on selected outcomes of qualitative and quantitative field research conducted in Mitrovica in 2017 and 2018 as well as results of other studies devoted mostly to Mitrovica but also to Mostar, Vukovar, Skopje and Sarajevo. Przybysze i miejscowi. Niewidoczne granice wśród mieszkańców podzielonego miasta na BałkanachBadania nad podzielonymi miastami na Bałkanach koncentrują się głównie na podziałach etnicznych/narodowych. Jednak, czy ta perspektywa jest odpowiednia i wystarczająca do opisania miast pokonfliktowych na Bałkanach? To pytanie nie wynika tylko z faktu, że każde miasto jest w jakiś sposób podzielone lub rozdrobnione. Bardziej istotny, a jednocześnie mniej znany jest fakt, że niestabilna struktura populacji tych miast jest znacznie bardziej złożona, a relacje międzygrupowe – znacznie bardziej skomplikowane, niż przedstawiają to dominujące narracje o podzielonych miastach przypisujące kluczowe znaczenie rozłamom etnicznym/narodowym. Tymczasem, nie doceniając znaczenia innego rodzaju relacji w społeczeństwie oraz dynamiki wysoce zmiennej struktury społecznej, nie można odkryć rzeczywistej natury relacji międzygrupowych w podzielonym mieście.Głównym celem artykułu jest przedstawienie współczesnego stanu między- i wewnątrzgrupowych relacji w podzielonym mieście, ze szczególnym uwzględnieniem statusu mieszkańców Mitrowicy. Artykuł jest przede wszystkim studium przypadku miasta Mitrowica (Kosowo) uzupełnionym o odniesienia do innych podzielonych miast na Bałkanach. Artykuł opiera się na wybranych wynikach jakościowych i ilościowych badań terenowych przeprowadzonych w Mitrowicy w 2017 i 2018 roku, jak również na wynikach innych badań poświęconych głównie Mitrowicy, ale także Mostarowi, Vukovarowi, Skopje i Sarajewu.


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