Efficient thrust enhancement by modified pitching motion

Thrust and/or efficiency of a pitching foil (mimicking a tail of swimming fish) can be enhanced by tweaking the pitching waveform. The literature, however, show that non-sinusoidal pitching waveforms can enhance either thrust or efficiency but not both simultaneously. With the knowledge and inspiration from nature, we devised and implemented a novel asymmetrical sinusoidal pitching motion that is a combination of two sinusoidal motions having periods T1 and T2 for the forward and retract strokes, respectively. The motion is represented by period ratio $\mathrm{\mathbb{T}} = {T_1}/T$ , where T = (T1 + T2)/2, with $\mathrm{\mathbb{T}} > 1.00$ giving the forward strokes (from equilibrium to extreme position) slower than the retract strokes (from extreme to equilibrium position) and vice versa. The novel pitching motion enhances both thrust and efficiency for $\mathrm{\mathbb{T}} > 1.00$ . The enhancement results from the resonance between the shear-layer roll up and the increased speed of the foil. Four swimming regimes, namely normal swimming, undesirable, floating and ideal are discussed, based on instantaneous thrust and power. The results from the novel pitching motion display similarities with those from fish locomotion (e.g. fast start, steady swimming and braking). The $\mathrm{\mathbb{T}} > 1.00$ motion in the faster stroke has the same characteristics and results as the fast start of prey to escape from a predator while $\mathrm{\mathbb{T}} < 1.00$ imitates braking locomotion. While $\mathrm{\mathbb{T}} < 1.00$ enhances the wake deflection at high amplitude-based Strouhal numbers (StA = fA/U∞, where f and A are the frequency and peak-to-peak amplitude of the pitching, respectively, and U∞ is the freestream velocity), $\mathrm{\mathbb{T}} > 1.00$ improves the wake symmetry, suppressing the wake deflection. The wake characteristics including wake width, jet velocity and vortex structures are presented and connected with $S{t_d}( = fd/{U_\infty })$ , ${A^{\ast}}( = A/d)$ and $\mathrm{\mathbb{T}}$ , where d is the maximum thickness of the foil.

Olódumare and Esu in Yorubá Religious Thought

Theological and philosophical debates on deities do not end easily; rather they open new vistas of understanding and further argumentation. In a previous work, I argued that there are two pairs of Olódumare and Es̩u in contemporary Yorubá religious thought and praxis. This conclusion was to navigate the extreme position that Olódumare and the Christian God have nothing in common. Although Segun Ogungbemi recently maintained the strict theological and moral differences between Olódumare and God using existential lens, he has not addressed the practical reality instantiated by the contemporary Yorubá diverse worshipers. Danoye Ogúntó̩lá-Láguda’s position on Olódumare and Es̩u is also slightly different from Ogúngbemí’s, although the former maintains a more practical posture. From their arguments I propose, in addition to my earlier two-pair argument that contemporary Yorubá may have four pairs of Olódumare and Esu: the first pair is autochtho ̩ - nous to the Yorubá, the second is Christian, the third Islamic, and the fourth, philosophical.

Turning discontent into votes: Economic inequality and ethnic outbidding

Ethnic outbidding, where parties adopt ever more extreme positions to capture electoral advantage, has become an increasingly common practice among ethnic parties. As economic issues have often served as a catalyst for ethnic tension, increasing levels of economic inequality should lead parties to adopt more extreme positions in an attempt to outbid one another. Furthermore, as their economic and ethnic platforms will appeal to the same ethnically defined constituency, ethnic outbidding should be more effective where inequality is high. Using a sample of over 150 ethnonational parties in Europe between 2011 and 2017, this paper finds that inequality is linked to increasing ideological extremism along a number of policy dimensions. Employing local-level voting data for Romania and Slovakia, we show that higher inequality makes adopting a more ideological extreme position a more successful electoral strategy, especially where economic issues are ethnically salient.

Quantification of Tourism Sector Parameters Related to Competitiveness of Countries According to Macroeconomic Indicators

The paper investigates the relations of the macroeconomic indicators related to the competitiveness of the tourism sector among the explored countries. The tourism sector plays an important role with the purpose of contributing to the economy of each country and, thus, its competitiveness among the other countries. The fundamental aim of the paper is to investigate the relations between the macroeconomic indicators related to tourism and their influence on the economy of the countries. The data set comprises the eight macroeconomic indicators, of which the four ones are related to the gross domestic product, the two ones to employment, the penultimate one to investment, and the last one to expenditure. The observed period covers the years 1995 to 2019. The Euclidean distance is employed to evaluate the similarity of the countries and the cluster analysis to group them successively. There are several patterns visible in the analysis outcome. Firstly, the countries that behave differently for both groups of the indicators with Mexico at the top position. Secondly, the countries with considerable change throughout the observed period where Greece stands at the most extreme position for the gross domestic product indicators and Hungary in the case of the other economic indicators. Thirdly, Chile remains at the evenest position throughout the whole explored period for the first group of the indicators and the United States for the second group of the indicators. Finally, Australia has almost the same development for both groups at the evenest tendency.

Social and Network Capital: the Relationship Between Concepts in a Network Approach

This article explores the differences between “social capital” and “network capital”, which are used in the context of network reflection. It is emphasized, that both capitals are interpretative variables and can be seen differently, depending on a semantic context. Every social structure implies branched social relations. That is why methodological tools of network approach are “convenient” for the study of social capital. In its core we find nuances of the interpretation of social capital. They depend not only on the nature of network actors but also on the researcher’s focus, on the network connections configuration or their content. Regardless of the course of the research, social capital is necessary for understanding social networks and social processes and is a result of said processes. As regards network capital, it can be defined as a form of social capital giving access to resources through interpersonal relationships (relational dimension). Defining characteristics of such relationships are trust and mutuality. However, the semantic emphasis can be transferred from the nature of relations to their modern support technologies. And so network capital appears as a measure of the value of communications maintained through telecommunication channels. The extreme position to social and network capitals suggests that social capital should be removed from the network approach and be completely replaced by the network capital. Otherwise, science denies other social forms of capital with their social characteristics. The author pays special attention to the ways of studying social networks using the theoretical capabilities of network capital in all its interpretations. The standpoint of its disregard, individualistic, and group approaches are highlighted.

Evaluation of the Effect of Holding the Mandrel in the Extreme Position of the FQM Mill on the Formation of Surface Defects

Modern continuous mills FQM are high-performance technological units that allow you to get products of a wide range. The paper presents the results of the study of the effect of the time of holding the mandrel in the extreme position of the continuous mill FQM (Fine Quality Mill) on the probability of defect formation of surface defects. The problems of сcomputational simulation of the process of continuous rolling of pipes were set and solved. It is established that the increase in the holding time of the mandrel allows to reduce the sliding of the metal on the surface of the tool, and contributes to a stable process of removing the mandrel without the formation of defects on the inner surface of the draft pipe. The results of solving the problems of сcomputational modeling allowed to formulate technical recommendations aimed at reducing the probability of surface defects in the production of pipes at the FQM mill.

Maintenance or Change? Examining the Reinforcing Spiral Between Social Media News Use and Populist Attitudes

Citizens around the world increasingly express support for populism. Here, we apply the reinforcing spirals model to examine whether, and how, social media news use shapes populist attitudes over time. Specifically, we assess if using social media as a news source serves to maintain existing populist attitudes or facilitates a shift in attitudes to a more extreme position. A cross-sectional survey (N1 = 195) highlighted a positive correlation between social media news use and populist attitudes. A four-wave longitudinal survey (N2 = 386) further showed that this relationship reflects media and selection effects. Over a period of three months, more frequent social media news use predicted stronger populist attitudes at subsequent measuring points. In addition, higher levels of populist attitudes were related to more frequent social media news consumption in the following waves. However, the frequency of social media news use did not change over time and populist attitudes did not become stronger during the study period. Taken together, the findings indicate that social media news use contributed to the maintenance of populist attitudes at a stable level. There is no evidence to suggest social media news use predicted more extreme populist attitudes. We discuss these results with respect to the (potentially continued) rise of populism; we also critically reflect on the phenomenon of attitude polarization online.

From Suicide to Prostitution

This article focuses on Kant’s central belief that an individual’s humanity, her rational personhood, ought never be treated merely as a means. I focus on two paradigmatic cases of such treatment, for Kant, namely suicide and prostitution. In the case of suicide, the individual treats his own humanity merely as a means in completely eliminating it to escape from his miserable life. The case of prostitution is more complicated. It is not obvious how the prostitute’s rational personhood is compromised. An analysis of Kant’s views on prostitution and sexuality enables us to understand Kant’s concern that the prostitute is treated merely as a means. However, his more extreme position that the prostitute is reduced to the status of a thing for use is not supported by arguments. A woman’s use (or, rather, misuse) as a mere means, I explain, is insufficient to define her status as an object.

Experimental study on an overhead crane passing a rail track joint

Purpose. To confirm the theoretical conclusions that determining the load from the wheel impact with the joint of rails in the metal structures of overhead cranes used in the technological processes at ore mining and processing mills and integrated works and moving along the rail tracks requires that the dynamic magnification factor should take into account the trolley position. Methodology. To assess the load to which the crane metal structures are exposed the electric strain measurement method using direct bridge circuit was chosen. To calibrate the strain measurement system, the direct method was used, under which calibration is performed directly on the structure on which experimental studies will be carried out in the future. Findings. It was established that the dynamic magnification factor in the metal structure of the overhead crane had the following values when passing the last rail joints: 1.54 (with the trolley in the middle of the bridge), 2.46 (with the trolley at 0.25 of the crane span from the end beam), 3.33 (with the trolley in the extreme position). So, with the trolley being at a distance of 0.25 of the crane span from the end beam, the dynamic magnification factor is 74%, and with the trolley in the middle of the bridge, it is 46% of the dynamic magnification factor if the trolley is in its extreme position. Originality. The scientific novelty consists in the first experimental confirmation of the results obtained in the theoretical studies on the overhead crane passing the joints of the rail track with regard to the crane trolley position, which leads to changes in the stiffness of the main beam in the interval between the trolley and the final beam. Practical value. The results obtained enable calculations on the crane bridge metal structure during the design and repair of the main and end beams taking into account the value of the dynamic magnification factor, which allows increasing the reliability and durability of the crane metal structure as a whole.