Optimal insulation of ducts in extraterrestrial applications

Optimum insulation thickness of a circular duct subjected to external radiative heat transfer is studied for a given amount of insulation material. A circular duct through which fluid is transported from one end to the other is considered. The thickness of the insulation is assumed to be linearly varying since this is easy to implement in practice. Thus the slope of the insulation thickness is considered as the parameter for optimum insulation. Variations of the bulk temperature of the fluid as well as the temperature of the outer surface of the insulation are evaluated. It is shown that linearly decreasing insulation thickness with minimum slope provides the best insulation under the radiation heat transfer condition. Copyright © 2004 John Wiley & Sons, Ltd.     

The effects of hyperbaric oxygen on normal and ischemic colon anastomoses

A pregnant woman with transient gastric obstruction was fed by enteral nutrition alone for 11 wk and 6 d. Her body mass index of 23.2 kg/m2 before pregnancy declined to 21.8 kg/m2 after delivery. Although she did not gain weight during enteral nutrition, fetal growth, estimated by ultrasonography, was normal, and she delivered a 3030-g female infant at 38 wk gestation. The blood laboratory data during pregnancy and the breast milk after pregnancy were also normal. The results suggest that factors other than maternal weight gain alone should be considered in the evaluation of nutritional status for the pregnant woman.     

Identification of dermatophytes as possible agents in clinically and microbiologically diagnosed dermatophytosis

In this study we have investigated the distribution of dermatophyte species clinically and microbiologically on 110 patients with dermatophytosis. The distribution of the dermatophytes according to the localization sites are: Tinea Capitis 13 (11.8%), T. Corporis 12 (10.9%), T. Inguinalis 22 (20%), T. Pedis et Manum 47 (42.7%), T. Unguinum 16 (14.5%). The species of dermatophytes which have been cultured were, Trichophyton rubrum 32 (29%), T. mentagrophytes 32 (29%), T. schoenleini 4 (3.6%), T. tonsurans 1 (0.9%), Epidermophyton floccosum 16 (14.5%), Microsporum canis 1 (0.9%), M. audouini 1 (0.9%), various molds 3 (2.7%) and also number of negative cultures obtained were 20 (18.1%).     

Maintenance strategies following the expiration of warranty

The authors study two types of replacement policies, following the expiration of warranty, for a unit with an IFR failure-time distribution: (1) the user applies minimal repair for a fixed length of time and replaces the unit by a new one at the end of this period; and (2) the unit is replaced by the user at first failure following the minimal repair period. In addition to stationary strategies that minimize the long-run mean cost to the user, the authors also consider nonstationary strategies that arise following the expiration of a nonrenewing warranty. Following renewing warranties, they prove that the cost rate function is pseudo-convex under a fixed maintenance period policy. The same result holds under nonrenewing repair warranties, and nonrenewing replacement warranties when the optimal maintenance period of each cycle is determined as a function of the age of the item in use at the end of the warranty period     

Effects of different surface treatment methods on the bond strength of composite resin to porcelain

In this study failures of composite resin/ porcelain interfaces under shear loading were examined. Porcelain firing were made onto metal cylinders and porcelain surfaces were roughened with burrs or treated with hydrofloric acid gel and/ or sandblasted with a Microetcher. Two silane coupling agents were used in five groups, each of which had 22 samples. All of the treated samples were restored with a hybrid-type composite resin. Then each group was divided into two subgroups according to storage times of 24 h and 30 days. After thermocyling the samples which were stored for 30 days, all of the groups were subjected to shear force at the composite resin/porcelain interface until fracture occurred. The results showed that there were differences both in the 24-h and 30-day storage period bond strengths between the various surface treatment methods. The samples treated with all three of the Microetcher, hydrofloric acid and silane exhibited the highest shear bond values after 24 h storage, followed by the microetched/silane and the hydrofluoric acid/silane groups (F: 570.31, P: 0.00). After 30 days, the highest mean shear bond strength values were again with samples treated by all three processes. The storage period and thermocycling decreased the bond strength of samples, however, there was a significant difference among groups (F: 1388-55, P: 0.00). Silane pre-treatment of porcelain was important as the mean bond strength of sandblasted/etched specimens were significantly lower than the other groups which were treated mechanically, in 24 h. Sandblasting seems to have little effect on the bonding. The comparison of 24-h and 30-day samples have also significant difference (F: 91.4376, P: 0.00).     

Urinary neopterin excretion and dihydropteridine reductase activity in rheumatoid arthritis

A 61-day short-term prospective study comparing the efficacy of Chemiron capsules (Ferrous Fumarate 300 mg, Folic Acid 5 mg, Vitamin B12 10 ug, Vitamin C 25 mg, Magnesium sulphate, 0.3 mg and Zinc Sulphate 0.3 mg) with conventional ferrous gluconate and folic acid administration has shown that both haematinic regimens improve haematological indices in normal pregnant women. A significant rise in haemoglobin was seen in the Chemiron group on days 5 and 19 whereas a significant increase in packed cell volume was observed on days 5, 19 and 61. There were no significant differences between the mean value of platelets during the therapy period in either group. A significant rise in the mean reticulocyte values could be demonstrated in the Chemiron group throughout the study period. This study further shows that Chemiron has a better haematological effect than Ferrous Gluconate at the dosage used.     

Friction welding of Al-Al,Al-steel,and steel-steel samples

Friction welding of Al- Al, Al- steel, and steel- steel studs is compared. Transient heat generation and temperature rise during the welding process were modeled. Tensile tests and microhardness measurements across the weld zone were carried out. The metallurgical changes in the heat- affected zone were examined by SEM. Temperature rise at the interface plane was computed and related to weld properties. The affecting parameters on weld quality were identified by statistical analysis. Results show that interaction of weld parameters significantly affect yield, tensile, and breaking strength, and the heat- affected zone on the Al side is wider for Al-steel welds.     

Design of Adaptive Robot Control System Using Recurrent Neural Network

The use of a new Recurrent Neural Network (RNN) for controlling a robot manipulator is presented in this paper. The RNN is a modification of Elman network. In order to solve load uncertainties, a fast-load adaptive identification is also employed in a control system. The weight parameters of the network are updated using the standard Back-Propagation (BP) learning algorithm. The proposed control system is consisted of a NN controller, fast-load adaptation and PID-Robust controller. A general feedforward neural network (FNN) and a Diagonal Recurrent Network (DRN) are utilised for comparison with the proposed RNN. A two-link planar robot manipulator is used to evaluate and compare performance of the proposed NN and the control scheme. The convergence and accuracy of the proposed control scheme is proved.     

Rheological properties of gluten-free bread formulations

In this study, the rheological properties of rice bread dough containing different gums with or without emulsifiers were determined. In addition, the quality of rice breads (volume, firmness and sensory analysis) was evaluated. Different gums (xanthan gum, guar gum, locust bean gum (LBG), hydroxyl propyl methyl cellulose (HPMC), pectin, xanthan–guar, and xanthan–LBG blend) and emulsifiers (Purawave^™ and DATEM) were used to find the best formulation for gluten-free breads. Rice dough and wheat dough containing no gum and emulsifier were used as control formulations. The rice dough containing different gums with or without emulsifiers at 25 °C showed shear-thinning behavior with a flow behavior index (n) ranging from 0.33–0.68 (except pectin containing samples) and consistency index (K) ranging from 2.75–61.7 Pa sⁿ. The highest elastic (G′) and loss (G″) module were obtained for rice dough samples containing xanthan gum, xanthan–guar and xanthan–LBG blend with DATEM. When Purawave^™ was used as an emulsifier, dough samples had relatively smaller consistency index and viscoelastic moduli values compared to DATEM. The viscoelastic parameters of rice dough were found to be related to bread firmness. Addition of DATEM improved bread quality in terms of specific volume and sensory values.