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31.
We propose a controller for a class of 2-DOF underactuated mechanical systems with discontinuous friction in the unactuated
joint. The control objective is the regulation of the unactuated variable while the position and speed of the actuated joint
remain bounded. The unactuated joint is considered as a mechanical system with discontinuous friction but continuous, artificial
control input given by a term depending on the actuated positions and velocities. The proposed controller guarantees the convergence
of the position error of the unactuated joint to zero, and it is robust with respect to some uncertainty in the discontinuous
friction coefficients. We illustrate the technique with its application to two systems. 相似文献
32.
We investigate the effects of delaying the time to recovery (delayed recovery) and of nonuniform transmission on the propagation of diseases on structured populations. Through a mean-field approximation and large-scale numerical simulations, we find that postponing the transition from the infectious to the recovered states can largely reduce the epidemic threshold, therefore promoting the outbreak of epidemics. On the other hand, if we consider nonuniform transmission among individuals, the epidemic threshold increases, thus inhibiting the spreading process. When both mechanisms are at work, the latter might prevail, hence resulting in an increase of the epidemic threshold with respect to the standard case, in which both ingredients are absent. Our findings are of interest for a better understanding of how diseases propagate on structured populations and to a further design of efficient immunization strategies. 相似文献
33.
Benito Alcaide Gerardo Escobar Rafael Pérez-Ossorio Joaquin Plumet 《Journal of heterocyclic chemistry》1984,21(3):919-921
The carbonyl group of substituted 5-benzoyl-4,5-dihydro-1,2,4-oxadiazoles can be reduced by lithium aluminium hydride at low temperature without ring opening. Mixtures of the two related diastereoisomeric benzylalcohols are obtained. Configurations were assigned by 1H-nmr. 相似文献
34.
David Jacob Joaquin Fernández-Rossier 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(10):210
Quantum spin tunneling and Kondo effect are two very different quantum phenomena that produce the same effect on quantized spins, namely, the quenching of their magnetization. However, the nature of this quenching is very different so that quantum spin tunneling and Kondo effect compete with each other. Importantly, both quantum spin tunneling and Kondo effect produce very characteristic features in the spectral function that can be measured by means of single spin scanning tunneling spectroscopy and allows to probe the crossover from one regime to the other. We model this crossover, and the resulting changes in transport, using a non-perturbative treatment of a generalized Anderson model including magnetic anisotropy that leads to quantum spin tunneling. We predict that, at zero magnetic field, integer spins can feature a split-Kondo peak driven by quantum spin tunneling. 相似文献
35.
Francisco Javier García-Fernndez Alba Estela García-Fernndez Ichiro Ikuta Eduardo Nava Julian Solis García del Pozo Joaquin Jordan Maria F. Galindo 《Molecules (Basel, Switzerland)》2021,26(4)
Dimethyl fumarate is a cytoprotective and immunomodulatory drug used in the treatment of multiple sclerosis. We performed a bibliometric study examining the characteristics and trends of the top 100 cited articles that include dimethyl fumarate in the title. On 21 September 2020 we carried out an electronic search in the Web of Science (WOS), seeking articles that include the following terms within the title: dimethyl fumarate, BG-12, or Tecfidera. To focus our investigation on original research, we refined the search to include only articles, early access, others, case report, and clinical trials. We obtained a total of 1115 items, which were cited 7169 times, had a citation density of 6.43 citations/item, and an h-index of 40. Around 2010, there was a jump in the number of published articles per year, rising from 5 articles/year up to 12 articles/year. We sorted all the items by the number of citations and selected the top 100 most cited (T100). The T100 had 4164 citations, with a density of 37 citations/year and contained 16 classic research articles. They were published between 1961 and 2018; the years 2010–2018 amassed nearly 80% of the T100. We noted 17 research areas with articles in the T100. Of these, the number one ranking went to neurosciences/neurology with 39 articles, and chemistry ranked second on the T100 list with 14 items. We noticed that the percentage of articles belonging to different journals changed depending on the time period. Chemistry held the highest number of papers during 1961–2000, while pharmacology andneurosciences/neurology led the 2001–2018 interval. A total of 478 authors from 145 institutions and 25 countries were included in the T100 ranking. The paper by Gold R et al. was the most successful with 14 articles, 1.823 citations and a density of 140.23 citations/year. The biotechnological company Biogen led the T100 list with 20 articles. With 59 published articles, the USA was the leading country in publications. We concluded that this study analyzed the use of and research on dimethyl fumarate from a different perspective, which will allow the readership (expert or not) to understand the relevance of classic and recent literature on this topic. 相似文献
36.
Summary Cobalt(II), nickel(II) and copper(II) complexes [M(CM)2]X2 (X = BF4 or NO3) have been prepared with cimetidine (CM). Powder data, molar conductivities, magnetic moments, i.r. and electronic spectra support apseudo-octahedral stereochemistry with MN2N
2
S2 chromophore and tentative structures are proposed for the complexes. Their properties are compared with these of previously prepared complexes. 相似文献
37.
Ring opening of furans can be accomplished with the title reagent to afford cis-enediones stereospecifically, with great advantages over the hazardous MCPBA. 相似文献
38.
M. Liu-Gonzalez F. Sanz-Ruiz Eduardo. E. Chufán Jose C. Pedregosa Joaquin Borras-Tortonda 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(10):1132-1134
In the X-ray crystal structure of the title complex, [Ni(C4H13N3)2](C2H3N4O2S2)Cl·H2O, the coordination polyhedron is composed of non-centrosymmetric [Ni(diethylenetriamine)2]2+ cations in which the triamine ligands coordinate to the metal centre as tridentate ligands in a facial position. The NiII ions are linked to six N atoms in an octahedral arrangement, slightly compressed in one extreme. The sulfonamide behaves as a counter-ion instead of as a ligand. Important information about the deprotonated sulfonamide group conformation has been obtained. 相似文献
39.