A new nonlinear gain structure for PD‐type controllers in robotic applications

This article introduces a generic enhancement to certain proportional plus differential (PD)‐type, joint‐space controllers for robotic manipulators that can be utilized to reduce peak levels of servo output without increasing the duration of the transient response. This enhancement takes the form of nonlinear, partially hyperbolic multipliers that are applied to re‐scale the error signal gains. The rationale prompting the design of the aforementioned gain structure is discussed at length, and a mathematical formulation of the modified control law is presented for application to both position and full trajectory control. The stability of the suggested control strategy is addressed, and numerical simulations involving a three degree of freedom (3‐DOF) robot model are presented to demonstrate quantitatively the potential benefits of implementing such. ©1999 John Wiley & Sons, Inc.     

Dispersion of Alumina and Silicon Carbide Powders in Alumina Sol

Dispersion of Al₂O₃ and SiC particles in an alumina sol has been investigated through determination of particle-size distribution, zeta potential, and agglomerate morphology. The particle size of Al₂O₃ and SiC (as determined by the particle-size analyzer) is strongly affected by the presence of alumina sol in the solution. The average agglomerate size is decreased by at least 50%. The zeta potential of Al₂O₃ in 1 M alumina sol increases slightly, whereas that of SiC reverses its sign over a wide range of pH values. It is proposed that these effects are caused by AlO₄Al₁₂(OH)₂₄(H₂O)⁷⁺₁₂ sol clusters (1-2 nm in size) that are absorbed on the surface of the large (1-5 µm) ceramic particles. The electrostatic and steric effects of the cluster absorption help to control the dispersion and stabilize the suspension of ceramic particles in the alumina sol during wet processing. It is expected that the alumina-sol clusters can be used as an efficient, clean dispersant for single-phase and composite ceramic powders.     

The Extractable and Bound Condensed Tannin Content of Leaves from Tropical Tree,Shrub and Forage Legumes

The extractable, protein-bound and fibre-bound condensed tannin (CT) concentrations in the leaves of tropical legumes grown in both Colombia and Northern Australia were determined by the butanol–HCl method, whilst extractable CT was also determined by the vanillin–HCl method. With the exception of Senna siamea all species contained CT. The very high CT concentration found in many plants growing in Colombia may have been partly due to soil fertility being much lower at the Colombian than the Northern Australian site. Acacia boliviana , Arachis pintoi , Centrosema latidens , Senna velutina and Gliricidia sepium contained <55 g total CT kg⁻¹ DM, which suggests that they could comprise a reasonable proportion of ruminant diets. All other species grown in South America contained 100–240 g CT kg⁻¹ DM, which suggests that they should only be fed in small amounts as supplements to dilute the CT concentration. Leucaena species and Calliandra calothyrsus grown in Northern Australia contained intermediate concentrations of total CT (60–90 g kg⁻¹ DM). Most species contained 70–95% of total CT as extractable CT, with the exception of Flemingia macrophylla , where 60% was extractable and 40% bound, and Gliricidia sepium , where almost all the CT was bound to protein. Values for Flemingia macrophylla differed between accessions. Extractable CT determined with vanillin–HCl was generally higher than extractable CT determined with butanol–HCl. Three accessions showed negligible (<1 g kg⁻¹ DM) extractable CT with butanol–HCl but 10–12 g extractable CT kg⁻¹ DM with vanillin–HCl. Two accessions showed undetectable levels of extractable CT but substantial levels of protein-bound CT, illustrating the importance of using a bound CT method for identifying forages containing CT. Relative to freeze drying, oven drying of Leucaena species reduced the concentration of extractable CT and increased concentrations of bound CT. The significance of the results for the nutrition of ruminant livestock are discussed, including the possible roles of protein-bound and fibre-bound CT.     

Stability of Cholesterol and Paprika Carotenoids in Egg Powders as Influenced by Dietary and Processing Treatments

The effects of dietary α-tocopherol and/or oleoresin paprika (OP) on cholesterol and carotenoid stability in egg powders during spray drying and subsequent storage were investigated. Cholesterol oxidation and loss of carotenoids in eggs dried with a direct gas-fired spray dryer were greater ( P< 0·05) than in eggs dried using an indirect (electric) heating system. Dietary supplementation of α-tocopherol acetate (200 mg kg⁻¹ feed) significantly increased ( P< 0·01) the oxidative stability of cholesterol and carotenoids in eggs dried with the direct heating system. Supplementation of OP (7·5 μg g⁻¹ egg lipids) through diet or by direct addition to liquid eggs did not affect the formation of cholesterol oxidation products (COPS) during storage. However, increased concentrations of OP in liquid eggs (15 and 30 μg g⁻¹ lipids) suppressed the formation of COPS during processing and subsequent storage.     

Deposition of Carotenoids in Eggs from Hens Fed Diets Containing Saponified and Unsaponified Oleoresin Paprika

Deposition of carotenoids in saponified paprika (SP) and unsaponified oleoresin paprika (OP) in egg yolks as well as the dietary level for desired pigmentation were evaluated. Sixty-four hens on a carotenoid-depletion diet were divided into two replicated groups of each of eight dietary treatments containing from 0 to 16 mg paprika carotenoids per kg feed. Colour and the carotenoid content of egg yolk increased linearly ( P< 0·01) with the amounts of paprika carotenoids in the diets. The colours of egg yolks from hens fed similar concentra-tions of OP or SP were not significantly different ( P< 0·01). A low dose (4 mg kg⁻¹) of OP or SP provided yolk colour equivalent to the colour of eggs in supermarkets. High-performance liquid chromatographic analyses showed that carotenoids deposited in the yolk are in the free alcohol form, regardless of the form of carotenoids in the diet. Capsanthin, the predominant carotenoid in paprika, was deposited in egg yolk less efficiently than zeaxanthin and lutein.     

长丝预湿上浆

研究了预湿在节省浆料和提高经纱质量方面的潜力和减少长丝上的油剂在浆液中溶入的可能性。讨论了和开发了预湿上浆技术。指出特别必须解决的问题是：纺丝油剂洗离、浆液浓度稀释、降低上浆剂需要量和它们之间的关系,以及污水的治理。     

Oligomeric procyanidins inhibit cell migration and modulate the expression of migration and proliferation associated genes in human umbilical vascular endothelial cells

The consumption of flavan-3-ols has been associated with reduced risk of cardiovascular diseases and improvements in vascular function. However, the nature of the flavan-3-ols responsible and the mechanisms underlying the vascular responses are not fully understood. We used microarrays to search for molecular changes in response to the exposure to (-)-epicatechin (EC), procyanidin dimer B2, and a mixture of oligomeric procyanidins in human umbilical vein endothelial cells (HUVECs). No gene expression changes were detected in HUVECs exposed to EC or dimer B2, however, the oligomeric procyanidins induced significant gene expression changes in both resting and TNF-alpha-stimulated cells. In particular, the expression of genes such as ADAMTS1, THBS1, ANGPT2, CYR61, ET-1, EDG3, and PDE4B involved in endothelial cell migration and proliferation, were substantially over-represented. Also, exposure to the oligomers arrested the cells at the G(0)/G(1 )phase and inhibited cell migration. These data show that human endothelial cells respond to oligomeric procyanidins by exhibiting a less migratory phenotype and by a general modulation of the expression of genes that are associated with key events in the angiogenic process. The molecular changes associated with procyanidin treatment identified in this study are consistent with the beneficial effects of flavan-3-ols on vascular function.     

Gamma-irradiation as a method of microbiological control,and its impact on the oxidative labile lipid component of <Emphasis Type="Italic">Cannabis sativa</Emphasis> and <Emphasis Type="Italic">Helianthus annus</Emphasis>

The effect of irradiation (0–20 kGy) on hemp and sunflower seeds was assessed, with specific reference to the oxidatively labile lipid component (unsaturated fatty acids and tocochromanols). Total protein, lipid, and solids content of the seeds did not vary with irradiation dose. Lipid hydroperoxide concentration increased significantly in the sunflower seeds (48 mmol kg⁻¹ lipid) and a significant increase in volatile secondary oxidation products was measured in both seeds (e.g. hexanal, heptanal, 1-penten-3-ol) with increasing irradiation dose. Irradiation at 5 kGy sterilised the seeds of all microbial contamination and irradiation doses of 20 kGy prevented germination. A loss of the antioxidant tocopherol was shown with increasing irradiation doses, although this was selective for specific tocopherol isoforms (α-tocopherol, β-tocopherol and γ-tocopherol).