Linking component importance to optimisation of preventive maintenance policy

In reliability engineering, time on performing preventive maintenance (PM) on a component in a system may affect system availability if system operation needs stopping for PM. To avoid such an availability reduction, one may adopt the following method: if a component fails, PM is carried out on a number of the other components while the failed component is being repaired. This ensures PM does not take system’s operating time. However, this raises a question: Which components should be selected for PM? This paper introduces an importance measure, called Component Maintenance Priority (CMP), which is used to select components for PM. The paper then compares the CMP with other importance measures and studies the properties of the CMP. Numerical examples are given to show the validity of the CMP

Influence of anionic structure on the dissolution of chitosan in 1-butyl-3-methylimidazolium-based ionic liquids

The high crystallization degree of chitosan and therefore its poor solubility in water and in most of the conventional organic solvents limits its extensive applications in practical processes. In this study, ionic liquids [C(4)mim][HCOO], [C(4)mim][CH(3)COO], [C(4)mim][CH(3)CH(2)COO], [C(4)mim][CH(3)CH(2)CH(2)COO], [C(4)mim][HOCH(2)COO], [C(4)mim][C(6)H(5)COO], [C(4)mim][CH(3)CHOHCOO] and [C(4)mim][N(CN)(2)] have been used to study the effect of anionic structure on solubility of chitosan and the possible dissolution mechanism in ionic liquids. For this purpose, solubilities of chitosan in these ionic liquids have been determined as a function of temperature, and hydrogen bond accepting ability of the ionic liquids has been estimated by (1)H NMR and solvatochromic UV/vis measurements. At the same time, the interaction between [C(4)mim][CH(3)COO] and chitosan in the chitosan + [C(4)mim][CH(3)COO] solution is investigated by (13)C NMR, and the regenerated chitosan from ionic liquids by addition of ethanol is characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). It is shown that in the ionic liquids investigated, [C(4)mim][CH(3)COO] is the most efficient ionic liquid for the dissolution of chitosan. Solubilities of chitosan increase almost linearly with increasing hydrogen bond accepting ability of the ILs. Both the anions and the [C(4)mim](+) cation play important roles in the dissolution of chitosan, possibly by the disruption of native hydrogen bonds in chitosan. In addition, good thermal stability has been observed for the regenerated chitosan

Effect of Alkyl Chain Length in Anions on Thermodynamic and Surface Properties of 1-Butyl-3-methylimidazolium Carboxylate Ionic Liquids

Carboxylate-anion-based imidazolium ionic liquids (ILs) are powerful solvents for cellulose and lignin. However, little is known about their fundamental physicochemical properties. In this work, 1-butyl-3-methylimidazolium carboxylate ILs 1-butyl-3-methylimidazolium formate ([C₄mim]­[HCOO]), acetate ([C₄mim]­[CH₃COO]), propionate ([C₄mim]­[CH₃CH₂COO]), and butyrate ([C₄mim]­[CH₃(CH₂)₂COO]), in which the alkyl chain length in the anions is being varied in contrast to the more usual studies where alkyl chain length in the cations is varied, have been synthesized and their densities and surface tensions have been determined experimentally at different temperatures. By using these data, the molar volume, isobaric expansivity, standard entropy, lattice energy, surface excess entropy, vaporization enthalpy, and Hildebrand solubility parameter have been estimated for these ILs. From the analysis of structure–property relationship, the effect of alkyl chain length in the anions on these physicochemical properties of the ILs has been assessed and the dissolution of cellulose and lignin in these ILs has been discussed. Such knowledge is expected to be useful for understanding the nature of this class of solvent for the dissolution of biomacromolecules

Broadly neutralizing and protective nanobodies against SARS-CoV-2 Omicron subvariants BA.1, BA.2, and BA.4/5 and diverse sarbecoviruses

The authors identify nanobodies from immunized alpaca with broadly neutralizing activity against SARS-CoV-1, SARS-CoV-2 variants, and major sarbecoviruses. One representative nanobody binds to a highly conserved epitope on RBD and protects K18-hACE2 mice from Omicron and Delta infection