Robust Speed Control of a Low Damped Electromechanical System Based on CRONE Control: Application to a Four Mass Experimental Test Bench

Robust speed control of a low damped electromechanical system with backlash is studied, controlled load angular speed being not measured. The proposed control strategy combines a Luenberger observer (load angular speed and load torque disturbance estimations) and a robust CRONE controller. The observer provides estimation of the load angular speed and of the disturbance torque applied on the load. Through the computation of only three independent parameters (as many as a PID controller), the CRONE controller permits to ensure the robust speed control of the load in spite of plant parametric variations and speed observation errors. The proposed control strategy is applied to a four mass experimental test bench.     

Quadratic Padé approximants and the intruder state problem of multireference perturbation methods

Simple and quadratic Padé resummation methods are applied to high‐order series from multireference many‐body perturbation theory (MR‐MBPT) calculations using various partitioning schemes (Møller–Plesset, Epstein–Nesbet, and forced degeneracy) to determine their efficacy in resumming slowly convergent or divergent series. The calculations are performed for the ground and low‐lying excited states of (i) CH₂, (ii) BeH₂ at three geometries, and (iii) Be, for which full configuration interaction (CI) calculations are available for comparison. The 49 perturbation series that are analyzed include those with oscillatory and monotonic divergence and convergence, including divergences that arise from either frontdoor or backdoor intruder states. Both the simple and quadratic Padé approximations are found to speed the convergence of slowly convergent or divergent series. However, the quadratic Padé method generally outperforms the simple Padé resummation. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

New synthetic route to diaminonitropyrazoles as precursors of energetic materials

Treatment of nitropyrimidine derivatives with (N-substituted) hydrazines (2 equiv.) gave 1-(substituted)-3,5-diamino-4-nitropyrazole, providing a very mild conversion of pyrimidines into pyrazoles. This reaction provided a convenient route to precursors for new efficient and insensitive explosives.     

Superconducting screen printed thick films of YBa2Cu3O7 and Bi1.6Pb0.4Sr1.6Ca2.4Cu3O10 on polycrystalline substrates

Thick films of YBa₂Cu₃O₇ and Bi_1.6Pb_0.4Sr_1.6Ca_2.4Cu₂O₁₀ have been prepared using a screen printing method on polycrystalline substrates. The films have been characterized by X-ray diffraction, electrical measurements and SEM observations. YBa₂Cu₃O₇ films exhibited T_c ranging from 80 to 87 K on Y₂BaCuO₅ substrates while Bi_1.6Pb_0.5Sr_1.6Ca_2.4Cu₃O₁₀ films on polycrystalline MgO reached the zero resistance state at 104 K with critical current densities of up to 10 A/cm² at 77 K.     

Laser ablated bismuth cuprate thin films preparation and effect of oxygen nonstoichiometry upon superconductivity

Thin films of Bi₂Sr₂CaCu₂O₈ and (Bi, Pb)₂Sr₂Ca₂Cu₃O₁₀ have been prepared on monocrystalline (100) MgO substrates, using a laser ablation method with post annealing treatment. The influence of substrate temperature and oxygen pressure during deposition were investigated. SEM observations, EDS analysis, electric and magnetic measurements have been used to characterize the films. Superconducting “2212” films, with T_c(R = 0) at 80–83 K and J_c (50 K) up to 5 × 10⁵ A/cm², have been currently achieved, while Pb-doped “2223” films exhibit T_c as high as 110 K with J_c = 5 × 10⁴ A/cm² at 77 K. The effect of annealing at low temperature (350°C) in an argon flow has been studied for the 2212 phase, it shows the influence of the oxygen non-stoichiometry, i.e. of the hole carrier density upon T_c's which can be measured up to 89 K (zero resistance).     

A Rapid Gas-Chromatography/Mass-Spectrometry Technique for Determining Odour Activity Values of Volatile Compounds in Plant Proteins: Soy,and Allergen-Free Pea and Brown Rice Protein

Plant-based protein sources have a characteristic aroma that limits their usage in various meat-alternative formulations. Despite being the most popular plant-based protein, the allergenicity of soy protein severely restricts the potential adoption of soy protein as an animal substitute. Thereby, allergen-free plant-protein sources need to be characterized. Herein, we demonstrate a rapid solid-phase-microextraction gas-chromatography/mass-spectrometry (SPME-GC/MS) technique for comparing the volatile aroma profile concentration of two different allergen-free plant-protein sources (brown rice and pea) and comparing them with soy protein. The extraction procedure consisted of making a 1:7 w/v aqueous plant protein slurry, and then absorbing the volatile compounds on an SPME fibre under agitation for 10 min at 40 °C, which was subsequently injected onto a GC column coupled to an MS system. Observed volatile concentrations were used in conjunction with odour threshold values to generate a Total Volatile Aroma Score for each protein sample. A total of 76 volatile compounds were identified. Aldehydes and furans were determined to be the most dominant volatiles present in the plant proteins. Both brown rice protein and pea protein contained 64% aldehydes and 18% furans, with minor contents of alcohols, ketones and other compounds. On the other hand, soy protein consisted of fewer aldehydes (46%), but a more significant proportion of furans (42%). However, in terms of total concentration, brown rice protein contained the highest intensity and number of volatile compounds. Based on the calculated odour activity values of the detected compounds, our study concludes that pea proteins could be used as a suitable alternative to soy proteins in applications for allergen-free vegan protein products without interfering with the taste or flavour of the product.     

Suberitane sesterterpenoids from the Antarctic sponge Phorbas areolatus (Thiele, 1905)

Following ecological and chemical screenings, the Antarctic sponge Phorbas areolatus was chemically investigated for the first time. Three new suberitane derivatives named isosuberitenone B, 19-episuberitenone B, and isoxaspirosuberitenone were identified together with the known compounds suberitenones A and B, and oxaspirosuberitenone after a thorough inspection of their NMR data. These compounds were found to exhibit moderate cytotoxic activity and their presence in this sponge rules out their use as a chemotaxonomic marker for Suberites sponges.     

Nucleophilic substitution with amines: dihydro-1,2,4,5-tetrazines are more useful precursors than 1,2,4,5-tetrazines

A one step synthesis of (di)alkylamino-substituted 1,2,4,5-tetrazines direct from 3,6-disubstituted-1,2-dihydro-1,2,4,5-tetrazine precursors is described. A comparative study revealed that the described method not only avoids the up-to-now required oxidation step but also lower reaction times and/or temperatures compared to usual protocols. The efficiency of the reaction was highlighted by a practical synthesis of 3,6-bis(methylamino)-1,2,4,5-tetrazine using aqueous methylamine. Other primary and secondary amines were also found to give disubstitution products when reacted with 3,6-bis(methylsulfanyl)-1,2,4,5-dihydrotetrazine.