An implementation of optimal control methods (LQI, LQG, LTR) for geostationary satellite attitude control

This paper investigates a new strategy for geostationary satellite attitude control using Linear Quadratic Gaussian (LQG), Loop Transfer Recovery (LTR), and Linear Quadratic Integral (LQI) control techniques. The sub-system satellite attitude determination and control of a geostationary satellite in the presence of external disturbances, the dynamic model of sub-satellite motion is firstly established by Euler equations. During the flight mission at 35000 Km attitude, the stability characteristics of attitude motion are analyzed with a large margin error of pointing, then a height performance-order LQI, LQG and LTR attitude controller are proposed to achieve stable control of the sub-satellite attitude, which dynamic model is linearized by using feedback linearization method. Finally, validity of the LTR order controller and the advantages over an integer order controller are examined by numerical simulation. Comparing with the corresponding integer order controller (LQI, LQG), numerical simulation results indicate that the proposed sub-satellite attitude controller based on LTR order can not only stabilize the sub-satellite attitude, but also respond faster with smaller overshoot.

Facile preparation of CuBi2O4/TiO2 hetero-systems employed for simulated solar-light selective oxidation of 4-methoxybenzyl alcohol model compound

The selective photocatalytic oxidation of organic substances is today considered one of the green techniques to synthesize important starting materials in different technological applications. This work reports an efficient, simple and cheap strategy for the synthesis of a new photocatalytic CuBi2O4-TiO2 (CBO/TiO2) heterosystem at room temperature. The prepared powders were characterized by X-ray diffraction (XRD), UV–Vis diffuse reflectance spectra (DRS), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. The photocatalytic activity was evaluated by performing a probe reaction, namely the partial oxidation of 4-methoxybenzyl alcohol (4-MBA) to 4-methoxybenzaldehyde (4-MBAld) in aqueous solution under irradiation of simulated sunlight. The CBO/TiO2 coupled systems showed a higher photoactivity than the single photocatalysts reaching a selectivity of 45% towards 4‑methoxy-benzaldehyde with an alcohol conversion of 77% after 4 h of irradiation. Furthermore, although a high alcohol conversion was achieved, the selectivity towards 4-MBAld was significant, unlike what has been reported in the literature for many heterogeneous photocatalytic reactions whose selectivity generally decreases significantly with the increasing conversion of the starting alcohol molecule. The improved photocatalytic activity could be attributed to the partial coverage of the TiO2 surface by CBO which reduces the subsequent oxidation of the formed aldehyde

BET Inhibition-Induced GSK3β Feedback Enhances Lymphoma Vulnerability to PI3K Inhibitors

The phosphatidylinositol 3 kinase (PI3K)-glycogen synthase kinase \u3b2 (GSK3\u3b2) axis plays a central role in MYC-driven lymphomagenesis, and MYC targeting with bromodomain and extraterminal protein family inhibitors (BETi) is a promising treatment strategy in lymphoma. In a high-throughput combinatorial drug screening experiment, BETi enhance the antiproliferative effects of PI3K inhibitors in a panel of diffuse large B cell lymphoma (DLBCL) and Burkitt lymphoma cell lines. BETi or MYC silencing upregulates several PI3K pathway genes and induces GSK3\u3b2 S9 inhibitory phosphorylation, resulting in increased \u3b2-catenin protein abundance. Furthermore, BETi or MYC silencing increases GSK3\u3b2 S9 phosphorylation levels and \u3b2-catenin protein abundance through downregulating the E2 ubiquitin conjugating enzymes UBE2C and UBE2T. In a mouse xenograft DLBCL model, BETi decrease MYC, UBE2C, and UBE2T and increase phospho-GSK3\u3b2 S9 levels, enhancing the anti-proliferative effect of PI3K inhibitors. Our study reveals prosurvival feedbacks induced by BETi involving GSK3\u3b2 regulation, providing a mechanistic rationale for combination strategies. In this study, Derenzini et al. demonstrate that BET inhibitors enhance lymphoma vulnerability to PI3K inhibitors by inducing GSK3\u3b2 feedback in a MYC-dependent manner and by downregulating E2-ubiquitin conjugating enzymes, which further enhance the feedback. These data provide the rationale for combining BET and PI3K inhibitors in lymphoma therapy

Visible-Light Photoreforming of Biomass Derivatives through MBi2O4-P25 Heterostructures: Study of the Influence of Metals (M = Cu, Ni, Zn, Co)

In this work, MBi2O4-P25 (M = Cu, Ni, Co, Zn) composites are successfully synthesized by a simple ball milling method by varying some parameters (rotation speed, rotation time, metal/TiO2 ratio) to optimize the preparation conditions. The noble metal-free TiO2-based photocatalysts are used to carry out the partial oxidation of glucose and glycerol with the simultaneous H2 production under simulated solar light irradiation. Starting from glucose, 2.6 mmol of H2 are obtained with a conversion of 34%, along with arabinose, formic acid and gluconic acid as main intermediates. By using glycerol, 3.2 mmol of H2 are produced, with 17% conversion and the production of dihydroxyacetone and glycolic acid. The composites exhibit higher activity than pure P25 and CuBi2O4 (CBO). The produced H2 amount is comparable to that reported in the literature by using Pt–TiO2 photocatalysts. This study offers a paradigm for the future design of bifunctional photocatalysts for simultaneous noble metal-free H2 production and biomass valorization under environmentally friendly conditions with a possible scale up of the process

A study of the phase transitions, electronic structures and thermodynamic properties of Mg2X (X = Ge, Si and Sn) under high pressure

In this work, we theoretically investigate phase transitions, electronic structures and thermodynamic properties of Mg2X (X = Ge, Si and Sn) under high pressures. To reach this goal, the total energy has been calculated by using the full-potential linearized augmented plane wave (FP-LAPW) method with generalized gradient approximation (GGA), local density approximation (LDA) and Engel–Vosko approximation (EV-GGA), which are based on the exchange-correlation energy optimization. The fully relaxed structure parameters of Mg2X compounds are in good agreement with the available experimental data. Our results demonstrate that the Mg2X compounds undergo two pressure-induced phase transitions. The first one is from the cubic antifluorite (Fm3¯m) structure to the orthorhombic anticotunnite (Pnma) structure in the pressure range of 3.77–8.78 GPa (GGA) and 4.88–8.16 GPa (LDA). The second transition is from the orthorhombic anticotunnite structure to the hexagonal Ni2In-type (P63m¯mc) structure in the pressure range of 10.41–29.77 GPa (GGA) and 8.89–63.45 GPa (LDA). All the structural parameters of the high pressure phases are analyzed in detail. Only a small difference in the structural parameters is observed at high pressures between the calculated and experimental results. The electronic and thermodynamic properties are also analyzed and discussed. The establishment of the metallic state of the Mg2X (X = Ge, Si and Sn) compounds at high pressure is confirmed

Insights into the optical and electrochemical features of CuAl2O4 nanoparticles and it use for methyl violet oxidation under sunlight exposure

International audienceHerein, the synthesis, optical, and electrochemical characteristics of the spinel CuAl2O4 synthesized by co-precipitation are the focus of this research. As per to the X-ray diffraction (XRD), the obtained sample crystallizes in a cubic symmetry (SG: fd-3m) with a lattice constant of 8.0790 Å. The TEM image revealed spherical nanoparticles with an average build of ∼9 nm and d-spacing of 0.248 nm of the reticular the planes (3 1 1), suggesting the formation of the CuAl2O4 crystalline structure. The optical and dielectric constants, including the extinction coefficient (k), refractive index n (λ), optical conductivity (σopt), dissipation factor (tan δ) and relaxation time (τ) were determined based on diffuse reflectance. The (C−2 - E) graph, plotted in Na2SO4 showed that CuAl2O4, is feature of n-type conduct with a flat band potential of 0.42 VRHE. The EIS spectroscopy displays a semicircle feature with the presence of a constant phase element (CPE) and a bulk resistance of 558 Ω cm2 that lowers to 462.7 Ω cm2 under visible irradiation. As application, the catalytic performance of CuAl2O4 was examined in the breakdown of Methyl violet dye (MV) under sunlight. Within 3 h, an abatement of 89% was obtained, and the oxidation of MV (10 mg/L) follows a first-order kinetic model with a half-life of 82 min. The catalyst can be reused without loss of activity for the first four cycles where •OH and •O2− are accountable of the MV oxidation. © 2022 Elsevier B.V