Strictly Positive Definite Functions on a Compact Group

We recognize a result of Schreiner, concerning strictly positive definite functions on a sphere in an Euclidean space, as a generalization of Bochner\u27s theorem for compact groups

The Bernoulli Family: Their Massive Contributions to Mathematics and Hostility Toward Each Other

Throughout the history of mathematics, there are several individuals with significant contributions. However, if we look at the contribution of a single family in this field, the Bernoulli probably outshines others in terms of both the number of mathematicians it produced and their influence on the development of mathematics. The most outstanding three Bernoulli mathematicians are Jacob I Bernoulli (1654-1705), Johann I Bernoulli (1667-1748), and Daniel Bernoulli (1700-1782), all three of whom were the most influential math experts in the academic community yet very hostile to each other. Their family structure and jealousy toward each other might have fueled their massive contributions to mathematics

Influence of Quasiperiodic Gravitational Modulation on Convective Instability of Liquid-Liquid Polymerization Front

The influence of quasiperiodic gravitational modulation on convective instability of polymerization front with liquid monomer and liquid polymer is studied. The model includes the heat equation, the concentration equation, and the Navier-Stokes equations under the Boussinesq approximation. The linear stability analysis of the problem is carried out and the interface problem is derived. Using numerical simulations, the convective instability threshold is determined and the boundary of the convective instability is obtained for different amplitudes and frequencies ratio

Power Quality Enhancement in Electricity Grids with Wind Energy Using Multicell Converters and Energy Storage

In recent years, the wind power industry is experiencing a rapid growth and more wind farms with larger size wind turbines are being connected to the power system. While this contributes to the overall security of electricity supply, large-scale deployment of wind energy into the grid also presents many technical challenges. Most of these challenges are one way or another, related to the variability and intermittent nature of wind and affect the power quality of the distribution grid. Power quality relates to factors that cause variations in the voltage level and frequency as well as distortion in the voltage and current waveforms due to wind variability which produces both harmonics and inter-harmonics. The main motivation behind work is to propose a new topology of the static AC/DC/AC multicell converter to improve the power quality in grid-connected wind energy conversion systems. Serial switching cells have the ability to achieve a high power with lower-size components and improve the voltage waveforms at the input and output of the converter by increasing the number of cells. Furthermore, a battery energy storage system is included and a power management strategy is designed to ensure the continuity of power supply and consequently the autonomy of the proposed system. The simulation results are presented for a 149.2 kW wind turbine induction generator system and the results obtained demonstrate the reduced harmonics, improved transient response, and reference tracking of the voltage output of the wind energy conversion system.Peer reviewedFinal Accepted Versio

Structural characteristics of simply connected planar sections with application to airfoils

The presented work is to develop a numerical computation program to determine the geometrical characteristics of arbitrary simply connected planar sections and applications to airfoils. In the literature, there are exact analytical solutions only for some simples’ geometries, such as circular, rectangular and elliptical sections. Hence our interest is focused on the search of approximate numerical solutions for more complex sections used in aeronautics. The used method is to subdivide the section in the infinitesimal triangular sections with a single observer within the area having a suitable position. The characteristics of any triangle, given by the positions of these three nodes are known in the literature. Using the principle of compound surfaces, one can determine the geometric characteristics of the airfoil surface. The analytic function of the airfoil boundary is obtained by using the cubic spline interpolation because the airfoil is given in the form of tabulated points. Error estimation is done to determine the accuracy of the numerical computation

Stress in closed thin-walled tubes of single box subjected by shear forces and application to airfoils

The presented work is to develop a numerical computation program to determine the distribution of the shear stress to shear in closed tubes with asymmetric single thin wall section with a constant thickness and applications to airfoils and therefore determining the position and value of the maximum stress. In the literature, there are exact analytical solutions only for some sections of simple geometries such as circular section. Hence our interest is focused on the search of approximate numerical solutions for more complex sections used in aeronautics. In the second stage the position of the shear center is determined so that the section does not undergo torsion. The analytic function of the boundary of the airfoil is obtained by using the cubic spline interpolation since it is given in the form of tabulated points

The Communicative Interpretation for Arab Social Mobility (Arab Social Movement)

The study aims to analyze the social mobility in the Arab countries in 2011, presenting an approach based on considering communication factors that played a crucial role in motivating young people and the Arab masses to participate and influence what was known as the Arab Spring. Indeed, that stage in the history of the media in Arab countries witnessed wide development in the use of satellite channels, websites, and smartphones. As the study shows, these technologies were employed as mechanisms that helped people interact, move, and participate. Based on the paradigm for the knowledge pyramid scheme, the study attempted to highlight the stages of information transmission from the first stage, which is the data stage, through the information stage, then the third stage, which is the knowledge stage, towards the final stage, which is the action stage. The study analyzes that overcoming the gradual stages of information transmission and passing from raw information to action led to the existence of the Arab social movement in the hands of activists who did not have a program or strategy for change in front of a movement that was able to overthrow old political regimes, but it did not have alternatives. As part of the analysis track, the study depends on a careful analysis of the roles of active groups in change. It pertains to the role of politicians, intellectuals, activists, and journalists

Long Term Ground Based Precipitation Data Analysis: Spatial and Temporal Variability

California is an area of diverse topography and has what many scientists call a Mediterranean climate. Various precipitation patterns exist due to El Niño Southern Oscillation (ENSO) which can cause abnormal precipitation or droughts. As temperature increases mainly due to the increase of CO2 in the atmosphere, it is rapidly changing the climate of not only California but the world. An increase in temperature is leading to droughts in certain areas as other areas are experiencing heavy rainfall/flooding. Droughts in return are providing a foundation for fires harming the ecosystem and nearby population. Various natural hazards can be induced due to the coupling effects from inconsistent precipitation patterns and vice versa. Using wavelets, we were able to identify anomalies of high precipitation and droughts within California\u27s 7 climate divisions using NOAA\u27s hourly precipitation data from rain gauges and compared the results with modeled data, SOI, and PDO. The identification of anomalies can be used to compare and correct remote sensing measurements of precipitation and droughts. Promising results show a possible connection with increasing tropical moisture activity

Comparison of dual antiplatelet therapy versus oral anticoagulation following transcatheter aortic valve replacement: A retrospective single-center registry analysis

Background: The choice of optimal antithrombotic regimen after transcatheter aortic valve replace-ment (TAVR) remains a matter of debate. The objective of this study was to compare both efficacy and safety outcomes based on the type of antithrombotic therapy prescribed after TAVR Methods: This is a retrospective analysis of 514 consecutive patients treated with either dual antiplate¬let therapy (DAPT) (n = 315; 61.3%) or oral anticoagulation (OAC) plus clopidogrel (n = 199; 38.7%) for a minimum of 3 months after TAVR followed by antiplatelet monotherapy or OAC only, respectively. Patients had pre-defined clinical and echocardiographic follow-ups at 30 days, 6 and 12 months. The key efficacy endpoint was a composite of all-cause death, myocardial infarction, stroke and valve throm¬bosis at 1 year. The key safety endpoint was the occurrence of life-threatening/major bleeding at 1 year. Results: Baseline characteristics did not differ between both groups, except for a higher incidence of atrial fibrillation in the OAC group. No significant differences in both efficacy and safety endpoints were observed at 30 days and 6 months. At 1 year, the key efficacy endpoint occurred in 21.5% of the DAPT group compared to 19.7% of the OAC group (p = 0.61). The key safety endpoint occurred in 25.1% and 27.8%, respectively (p = 0.53). However, after 1 year valve thrombosis was reported in 8 (2.5%) patients in the DAPT group but not in the OAC group (p = 0.02). Conclusions: OAC after TAVR seems to reduce the risk of clinical valve thrombosis without a statisti-cally significant increase in bleeding complications