Study on the compensation of error by stick-slip for high-precision table

A simple approach of compensating friction error of high-precision tables is proposed in this paper. On the basis of accurate prediction of the magnitude of the friction error and the place where it occurs, a compensator is first constructed which consists of an online friction error prediction model and rectangular compensation curves regarded as compensation pulses. Then by carrying out optimal compensation experiments several times, the parameters describing the rectangular compensation curve at certain positions can be obtained. Finally, the optimal parameters of the rectangular compensation curve at any position can be determined by interpolation and approximation. It has been shown that, the method to compensate friction error proposed in this paper can be applied to effectively compensate the friction error for all circular motions of high-precision tables.     

Asymmetric polymerization of N-substituted maleimides with organolithium — bisoxazolines complex

Asymmetric anionic polymerizations of achiral N-substituted maleimide (RMI) (N-cyclohexyl (CHMI), N-phenyl (PhMI), N-tert-butyl (TBMI)) by n-butyllithium (n-BuLi) or fluorenyllithium (FlLi) complexes of chiral bisoxazoline derivatives in toluene gave optically active polymers ([α]²⁵ ₄₃₅− 2.9° to − 8.2°). The polymers prerared with initiator of n-BuLi – 2,2′-bis(4,4′-isopropyl-,3-oxazoline) showed negative specific rotations (poly(RMI), [α]²⁵ ₄₃₅− 5.8° to − 8.2°) which were greater than those ([α]²⁵ ₄₃₅− 2.9° to − 5.9°) with other chiral 2,2′-bis(4,4′-alkyl-1,3-oxazoline) (alkyl group = iso-butyl and benzyl). Received: 29 July 1997/Revised: 27 August 1997/Accepted: 1 September 1997     

Plasma-polymerization of F-propene/acetylene and F-propene/ethylene mixtures and their gas permeability

Summary Plasma-polymerized thin films from the mixture ofF-propene and acetylene (C₂H₂) or ethylene (C₂H₄) were investigated by elemental analysis, infrared spectroscopy, and ESCA. The chemical composition for the plasma-polymers depended on these gaseous mixture composition. The F/C elemental ratio for the plasma-polymers decreased with increasing the C₂H₂ or C₂H₄ concentration, and at the same time the H/C ratio increased. The plasma-polymers were composed ofCF₃,CF₂,CF-CF_n,CF, andC-CF_n units. The addition of C₂H₂ or C₂H₄ depressed the formation of the plasma-poly-mers with highly-fluorinated carbon units such as CF₃ CF₂ groups, and encouraged that of polymers with less-fluorinated carbon units. Furthermore, such changes of the plasma-polymers in the chemical composition by adding C₂H₂ or C₂H₄ were favourable to improve gas separation abilities. The ratio of oxygen and nitrogen permeation coefficient increased from 1.7 to 3.5 by adding C₂H₂ of 50 mol% and also increased to 2.9 by adding C₂H₄ of 37.5 mol%. Less-fluorinated carbon units seem to play an important role in the separation from the oxygen/nitrogen mixture.     

Towards further internal heat integration in design of reactive distillation columns—Part II. The process dynamics and operation

In the first paper of this series, it has been demonstrated that the capital investment and operating cost can frequently be reduced substantially through seeking further internal heat integration between the reaction operation and separation operation for a reactive distillation column involving reactions with highly thermal effect. In this paper, the dynamics and operation of the resultant reactive distillation system is to be examined, with special emphasis focused on the dynamic effect of the supplementary internal heat integration. It has been found that seeking further internal heat integration can sometimes improve process dynamics and lessen difficulties in process operation. This outcome stems from the refined relationship between the reaction operation and separation operation involved and is of great significance in tightening process design for a reactive distillation column containing reactions with highly thermal effect.It should, however, be pointed out that seeking further internal heat integration might also confine severely the flexibility of the resultant reactive distillation column due to the reduction of mass transfer driving forces. When encountering a sharp increase in the product specification that is more relevant to the supplementary internal heat integration, the process might show deteriorated dynamic performance and can even converge to an undesirable steady state where the economical advantages of the supplementary internal heat integration are lost totally. Therefore, some effective measures to increase the redundancy of the resultant process design have to be taken to deal with the side-effect during process development.     

Production of MAG of CLA in a solvent-free system at low temperature with <Emphasis Type="Italic">Candida rugosa</Emphasis> lipase

We attempted to produce MAG of CLA through lipase-catalyzed esterification of a FFA mixture containing CLA (referred to as FFA-CLA) with glycerol. Screening of lipases showed that MAG-CLA was produced efficiently at 5°C with Penicillium camembertii, Rhizopus oryzae, and Candida rugosa lipases. Among them, C. rugosa lipase was selected because the lipase is widely used as a catalyst for oils and fats processing. The reaction was conducted with agitation of a 300-g mixture of FFA-CLA/glycerol (1∶5, mol/mol), a 200-U/g mixture of C. rugosa lipase, and 2% water. When the reaction was conducted at 30°C, the esterification scarcely proceeded, owing to inhibition of the reaction by glycerol. But the reaction at 5°C eliminated the inhibition and produced MAG efficiently: The degree of esterification reached 93.8% after 58 h, and MAG content in the reaction mixture was 88.4 wt%. To reduce the reaction time, the reactor was connected with a vacuum pump after 24 h, and the reaction was continued with dehydration at 5 mm Hg. The degree of esterification reached 94.7% after 24 h of dehydration (48 h in total), and MAG content increased to 93.0 wt%. Candida rugosa lipase acted a little more strongly on cis-9, trans-11 CLA than on trans-10,cis-12 CLA, but the contents of the two isomers in MAG obtained from a 48-h reaction were the same as the contents in FFA-CLA.     

Solid Solubility of GeO2 in SnO2

Subsolidus equilibrium relations were reexamined in the SnO₂-rich portion of the system GeO₂-SnO₂ (60 to 98 mol% SnO₂). A limited solid solution based on SnO₂ was confirmed; 4mol% GeO₂ dissolved in SnO₂ at 1250 C, and glass was formed on quenching over the compositional range above 4mol% GeO₂. Phase relutions in the system are discussed with reference to the polymorphism of GeO₂ and its glass-forming ability, and a possible phase diagram is given .     

Syntheses of chemical‐modified cellulose obtained from waste pulp

Chemical‐modified pulps were synthesized from four types of waste pulps (Pulp1–4) and succinic anhydride (SAn) or maleic anhydride (MAn). The solubility of the modified pulps was evaluated in common organic solvents, and their thermal properties were investigated by DSC measurement. The solubility of the modified pulps increased with an increasing degree of substitution (DS). However, no T_g or T_m of these modified pulps was confirmed. Pulps and modified pulps were graft‐polymerized with ε‐caprolactone (CL) in bulk and in DMAc/LiCl. Although the solubility of the graft copolymers was similar to modified pulps, some graft copolymers showed a T_g by the introduction of CL units. In the bulk, graft copolymers obtained from modified pulps and nonmodified pulps showed a T_g of about 75°C and no T_g, respectively. In DMAc/LiCl, the obtained graft copolymers from both modified and nonmodified pulps exhibited a T_g of 95–110°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2059–2065, 2003     

Syntheses and biodegradability of benzylated waste pulps and graft copolymers from PBzs and L‐lactic acid

Benzylated waste pulps (PBzs) were synthesized from treated waste pulp (Pulp), and benzyl chloride with phase transfer catalyst (PTC), and graft copolymers (PBz‐g‐LA) were synthesized from PBzs and L‐lactic acid (LA). Thermal properties, solubility, crystallinity, and biodegradability of the obtained PBzs and graft copolymers were investigated. PBzs with the degree of substitution (DS) higher than 1.5 showed T_g and T_m in DSC measurement. All PBz‐g‐LA exhibited no T_m. However, the graft copolymers obtained from lower DS PBzs having no T_g, exhibited T_g. The solubility of PBzs enhanced with increasing DS, and the crystallinity of PBzs reduced with increasing DS because of hydrophobicity and steric effect of benzyl groups. The solubility of graft copolymers was similar to that of original PBzs. Biodegradation tests for PBzs, Pulp, and graft copolymers were performed using cellulase in 0.1 M acetate buffer solution (pH 5.5) at 37°C. All samples showed biodegradability though the biodegradation rate decreased with increasing DS of PBz. In PBz‐g‐LA, the initial biodegradation rate was faster than that of original PBz because of hydrolysis of LA units. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2658–2664, 2004     

Size and surface modification of amorphous silica particles determine their effects on the activity of human CYP3A4 in vitro

Because of their useful chemical and physical properties, nanomaterials are widely used around the world - for example, as additives in food and medicines - and such uses are expected to become more prevalent in the future. Therefore, collecting information about the effects of nanomaterials on metabolic enzymes is important. Here, we examined the effects of amorphous silica particles with various sizes and surface modifications on cytochrome P450 3A4 (CYP3A4) activity by means of two different in vitro assays. Silica nanoparticles with diameters of 30 and 70 nm (nSP30 and nSP70, respectively) tended to inhibit CYP3A4 activity in human liver microsomes (HLMs), but the inhibitory activity of both types of nanoparticles was decreased by carboxyl modification. In contrast, amine-modified nSP70 activated CYP3A4 activity. In HepG2 cells, nSP30 inhibited CYP3A4 activity more strongly than the larger silica particles did. Taken together, these results suggest that the size and surface characteristics of the silica particles determined their effects on CYP3A4 activity and that it may be possible to develop silica particles that do not have undesirable effects on metabolic enzymes by altering their size and surface characteristics.     

Infrared spectra and ferro‐electricity of ultra‐thin films of vinylidene fluoride and trifluoroethylene copolymer

The structures of ultra‐thin films of vinylidene fluoride and trifluoroethylene copolymer were characterized using Fourier transform infrared reflection absorption spectroscopy (FTIR‐RAS), FTIR transmission spectroscopy (FTIR‐TRS), atomic force microscopy, and wide‐angle X‐ray diffraction. The ferro‐electricity was determined from polarization charge (a displacement (D)–electric field (E) hysteresis). FTIR‐RAS and FTIR‐TRS measurements showed that the molecular chains of polymers (crystal c‐axis) near the substrate tended to align parallel to the substrate. However, thermal annealing of the sample films at temperatures above 145 °C caused a marked change in molecular alignment of the polymer chains (crystal c‐axis) from parallel to normal to the substrate, and, further, caused a conformation change from trans to partially gauche forms. Copyright © 2007 Society of Chemical Industry