Parameter dependence of vortex interactions on a two-dimensional plunging plate

The structure and dynamics of the flow field created by a plunging flat-plate airfoil are investigated at a chord Reynolds number of 10,000 while varying plunge amplitude and Strouhal number. Digital particle image velocimetry measurements are used to characterize the shedding patterns and the interactions between the leading- and trailing-edge vortex structures (LEV and TEV), resulting in the development of a wake classification system based on the nature and timing of interactions between the leading- and trailing-edge vortices. The streamwise advancement of the LEV during a plunge cycle and its resulting interaction with the TEV is primarily dependent on reduced frequency; however, for Strouhal numbers above approximately 0.4, significant changes are observed in the formation of vortices shed from the leading and trailing edges, as well as the circulation of the leading-edge vortex. The functional form of the relationship between leading-edge vortex circulation and Strouhal number suggests that the Strouhal number dependence is more specifically a manifestation of the effective angle of attack. Comparison with low-Reynolds-number studies of plunging airfoil aerodynamics reveals a high degree of consistency and suggests applicability of the classification system beyond the range examined in the present work.     

Quantum chemical calculation,topological analysis,biological evaluation and molecular docking of allo-ocimenol against breast cancer

The main aim of this study is to identify the structural stability of allo-ocimenol and its molecular reactivity against breast cancer-associated proteins to confirm its anti-cancer capability using density function theory and molecular docking analysis. The structural optimization was carried out via the DFT/B3LYP technique with a 6-311++G (d,p) basis set. The molecular geometry and vibrational assignments of the Allo-Ocimenol molecule were analyzed through density functional theory (DFT). Through optimized molecular structure, the vibrational frequencies (FT-IR and FT-Raman) were assigned and related with experimentally observed vibrational frequencies and the UV spectrum was computed and experimentally confirmed. The allo-ocimenol's reactive activity was further analyzed through a computed molecular electrostatic potential surface. Utilizing the HOMO-LUMO energies and molecular electrostatic potential energy gap, the reactivity and molecular stability of the allo-ocimenol molecule was calculated. Mulliken and natural population analyses were used to determine the charge distribution across the allo-ocimenol atoms. The natural bond orbitals were used to demonstrate the bioactivity of the titled molecule. RDG evaluation was used to examine the weak interactions of the allo-ocimenol molecule. ELF and LOL analyses were utilized to investigate the topology of the allo-ocimenol molecule. Thermodynamic evaluation has been utilized to acquire values and asses the thermodynamic parameters that reveal the thermal stability of the title molecule. Allo-Ocimenol's anti-microbial activity was assessed through an in-vitro disc diffusion method, and its tumor inhibitory and pharmacokinetic properties were evaluated through an in-silico approach using molecular docking and ADMET investigation. Zones of clearance were seen in anti-microbial analyses at various concentrations, and the breast cancer target protein NAMPT established the greatest binding potential, with a docking value of −7.4 Kcal mol⁻¹.     

Zirconium oxide complex‐functionalized MCM‐41 nanostructure: an efficient and reusable mesoporous catalyst for oxidation of sulfides and oxidative coupling of thiols using hydrogen peroxide

Zirconium oxide complex‐functionalized mesoporous MCM‐41 (Zr‐oxide@MCM‐41) as an efficient and reusable catalyst is reported for the oxidation of sulfides into sulfoxides using hydrogen peroxide (H₂O₂) as the oxidant, with short reaction times in good to excellent yields at room temperature under solvent‐free conditions. Also, a simple and efficient method is reported for the oxidative coupling of thiols into corresponding disulfides in good to high yields using H₂O₂ as oxidant in the presence of Zr‐oxide@MCM‐41 as recoverable catalyst in ethanol at room temperature. A series of sulfides and thiols possessing functional groups was successfully converted into corresponding products. After completion of reactions the catalyst was easily separated with simple filtration from the reaction mixture and reused for several consecutive runs without significant loss of catalytic efficiency. The mesoporous catalyst was characterized using Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller surface area measurements, X‐ray diffraction, transmission and scanning electron microscopies, energy‐dispersive X‐ray spectroscopy and thermogravimetric analysis. Copyright © 2015 John Wiley & Sons, Ltd.     

Toughening of Poly(ethylene terephtalate) (PET) Bottle Wastes by Modified Styrene-Butadiene Rubber (SBR) Elastomer

Summary: Modified SBR was blended with dried PET bottle wastes in an internal mixer. During the process mechanical and morphological properties were studied. When PET bottle wastes were blended with unmodified SBR, the final blend had a rough morphology and low impact strength. In contrary, blending of PET with modified SBR lead to smooth and fine morphology. Utilizing grafted SBR in PET blends creates an enormous difference in particle size and morphology, which is a result of powerful interactions and effective chemical bonding between the components of the blend. The final product had high impact strength in comparison with PET and unmodified SBR blend. These results are mainly related to formation in situ of PET/SBR graft copolymer in interface, which is produced by chemical reaction among active maleic anhydride groups and active PET groups.     

An improved algorithm for online machine minimization

The online machine minimization problem seeks to design a preemptive scheduling algorithm on multiple machines — each job $j$ arrives at its release time $r_j$, has to be processed for $p_j$ time units, and must be completed by its deadline $d_j$. The goal is to minimize the number of machines the algorithm uses. We improve the $O(logm)$-competitive algorithm by Chen, Megow and Schewior (SODA 2016) and provide an $O\left(\frac{logm}{loglogm}\right)$-competitive algorithm.     

Paths to stability for college admissions with budget constraints

We study two-sided matching problem considered in Abizada (Theor Econ 11(2), 735–756, 2016), where one side (colleges) can make monetary transfers (offer stipends) to the other (students) subject to budget constraints. Colleges have strict preferences over sets of students and value money only to the extent that it allows them to enroll better or additional students. A student can attend at most one college and receive a stipend from it. Each student has preferences over college-stipend bundles. Although in the presence of budget constraints, the conditions that are essential for most of the results on stability in the literature fail, Abizada (Theor Econ 11(2), 735–756, 2016) shows that for this model a pairwise stable allocation always exists. In this paper, we show that starting from an arbitrary allocation, there is a sequence of allocations, each allocation being obtained from the previous one by “satisfying” a blocking pair, such that the final allocation is pairwise stable.     

Robust Stabilization and Synchronization of a Novel Chaotic System with Input Saturation Constraints

In this paper, the robust stabilization and synchronization of a novel chaotic system are presented. First, a novel chaotic system is presented in which this system is realized by implementing a sigmoidal function to generate the chaotic behavior of this analyzed system. A bifurcation analysis is provided in which by varying three parameters of this chaotic system, the respective bifurcations plots are generated and evinced to analyze and verify when this system is in the stability region or in a chaotic regimen. Then, a robust controller is designed to drive the system variables from the chaotic regimen to stability so that these variables reach the equilibrium point in finite time. The robust controller is obtained by selecting an appropriate robust control Lyapunov function to obtain the resulting control law. For synchronization purposes, the novel chaotic system designed in this study is used as a drive and response system, considering that the error variable is implemented in a robust control Lyapunov function to drive this error variable to zero in finite time. In the control law design for stabilization and synchronization purposes, an extra state is provided to ensure that the saturated input sector condition must be mathematically tractable. A numerical experiment and simulation results are evinced, along with the respective discussion and conclusion.     

Robust Variable-Step Perturb-and-Observe Sliding Mode Controller for Grid-Connected Wind-Energy-Conversion Systems

In order to extract efficient power generation, a wind turbine (WT) system requires an accurate maximum power point tracking (MPPT) technique. Therefore, a novel robust variable-step perturb-and-observe (RVS-P&O) algorithm was developed for the machine-side converter (MSC). The control strategy was applied on a WT based permanent-magnet synchronous generator (PMSG) to overcome the downsides of the currently published P&O MPPT methods. Particularly, two main points were involved. Firstly, a systematic step-size selection on the basis of power and speed measurement normalization was proposed; secondly, to obtain acceptable robustness for high and long wind-speed variations, a new correction to calculate the power variation was carried out. The grid-side converter (GSC) was controlled using a second-order sliding mode controller (SOSMC) with an adaptive-gain super-twisting algorithm (STA) to realize the high-quality seamless setting of power injected into the grid, a satisfactory power factor correction, a high harmonic performance of the AC source, and removal of the chatter effect compared to the traditional first-order sliding mode controller (FOSMC). Simulation results showed the superiority of the suggested RVS-P&O over the competing based P&O techniques. The RVS-P&O offered the WT an efficiency of 99.35%, which was an increase of 3.82% over the variable-step P&O algorithm. Indeed, the settling time was remarkably enhanced; it was 0.00794 s, which was better than for LS-P&O (0.0841 s), SS-P&O (0.1617 s), and VS-P&O (0.2224 s). Therefore, in terms of energy efficiency, as well as transient and steady-state response performances under various operating conditions, the RVS-P&O algorithm could be an accurate candidate for MPP online operation tracking.     

Some characterizations of Riesz spaces in the sense of strongly order bounded operators

Positivity - We investigate some properties of strongly order bounded operators. For example, we prove that if a Riesz space E is an ideal in $$E^{\sim \sim }$$ and F is a Dedekind complete Riesz...