Behavior of a nickel-base high-temperature alloy under hot-working conditions

The behavior of a Ni-Cr-Co base alloy with significant additions of Mo, Ti and Al (Nimonic 105) under hot working conditions was studied using hot compression tests in the temperature range of 1223 to 1523 K and strain rates between 0.38 and 64.3 s^-1. The microstructure of the Nimonic 105 is complex and the matrix contains second phases in the form of Ni₃ (Ti, Al) dispersion (γ′), various Cr and Ti carbides and titanium cyanonitrides inclusions. However, the results show that above the dissolution temperature of the γ′ phase, the alloy behaves like a single phase nickel-base solid solution from the point view of steady state flow stress-temperature-strain rate relationships, and the activation energies for hot working and static recrystallization. Under deformation conditions where the γ′ phase is present, as in the case of creep, the activation energy is almost doubled. The hot working temperature range giving sound product is 1280 to 1450 K (170 K) at a strain rate of 0.4 s^-1 and decreases to 1400 to 1480 K (80 K) at a strain rate of 65 s^-1. At temperatures above the higher limit the alloy suffers intercrystalline cracks due to hot shortness and at temperatures below the lower limit the alloy suffers transcrystalline cracks due to excessive strain hardening.     

Algorithms in the diagnosis and management of exotic diseases. XVI. Tuberculosis

With few exceptions, the incidence of left colon ischemia following abdominal aortic reconstruction has been reported to be one to 2 percent. All reports of such ischemic events are retrospective analyses of clinically manifest or autopsy. Fifty patients were studied prospectively to determine more accurately the incidence of this complication. Aortic reconstruction was performed in 23 patients for occlusive disease (OD) and in 27 for aneurysm disease (AD). No emergency operations were performed. All patients underwent colonoscopy within 4 days of operation. Three instances of colon ischemia were noted, an incidence of 6 percent (OD 4.3 percent, AD 7.4 percent). Each patient recovered uneventfully. Two patients had diarrhea, but only after colon ischemia was recognized. Arteriographic opacification of the inferior mesenteric artery by the superior mesenteric artery collateral (meandering mesenteric artery) was documented in 35 percent of patients with OD and in 27 percent of patients with AD. Colon ischemia did not develop when this collateral was identified. The inferior mesenteric artery was patent at the aorta in all who developed colon ischema. Although clinically significant colitis following aortic reconstruction is rare, colonoscopy after operation may prove to be valuable for early recognition of ischemic changes before clinical manifestations preclude effective management.     

Quantitative prediction of growth patterns of surface fatigue cracks in tension plates

Different methods of prediction of the aspect ratio variability of growing surface fatigue cracks in tension plates are compared with experimental data. The objective is to identify the most accurate method. The comparison is based on a quantitative criterion as well as on statistical examination of the level of agreement with the data. Fifty-eight cracks are analysed. The total number of data points is 450 taken from 20 references. The solutions evaluated include theoretical as well as empirical formulas. The comparison shows that it is possible to predict the aspect ratio variability with standard deviation <0.070.     

A Study of the Complexation Between Danazol and Hydrophilic Cyclodextrin Derivatives

Complexation between danazol, a steroid used for endometriosis, and both hydroxypropyl- β-cyclodextrin (HPCD) and sulfobutyl ether-β-cyclodextrin (SBE) was studied in solution and solid state. Complexation was evaluated in solution using solubility studies and proton magnetic resonance (¹H NMR) spectroscopy, and in the solid state using x-ray diffraction, Fourier-transform infrared spectroscopy (FTIR)), and dissolution studies. Solubility studies suggested the existence of a 1:1 complex between danazol and either HPCD or SBE. ¹H NMR showed that complexation occurs by inclusion of the isoxazole ring of danazol into the cyclodextrin cavity in both cases. Powder x-ray diffraction indicated that danazol existed in a crystalline noncomplexed form at low danazol-to-cyclodextrin ratios in the coprecipitates prepared by solvent evaporation method, while at higher ratios danazol existed in an amorphous complexed form. This ratio was 1:10 w/w for HPCD and 1:20 for SBE; the higher ratio in the case of SBE is attributed to early precipitation of danazol from the solvent used for preparation. FTIR studies showed that the complexation was accompanied by a shift of the O-H stretching of danatol hydroxyl group to a higher frequency, which is attributed to the disruption of the intermolecular hydrogen bonding. The dissolution rate of danazol from HPCD coprecipitates was higher than crystalline danazol in aqueous-isopropanolic medium, while SBE coprecipitates showed reduced dissolution rates due to the low solubility of SBE in isopropanol. However, SBE coprecipitates showed higher dissolution rates in water than in the isopropanolic medium.     

Fuzzy convex cones and functions for ordinary and parametric programs

The fuzzy sets is a notion which generalizes all types of the existing sets. Many authors were interested in this new type, so they defined many related notions and investigated more of their properties.In this paper we study a new concept of fuzziness called fuzzy convexity by introducing the notion of fuzzy convex sets for mathematical programs and also for parametric programs. The connections between these notions and the ordinary ones are given and some of their characterizations are investigated.     

OPTIMIZATION OF CONVECTIVE LONGITUDINAL FINS OF TRAPEZOIDAL PROFILE

This paper deals with optimum design of convective longitudinal fins of a trapezoidal profile. The optimum dimensions, and the associated heat dissipation, and efficiency are obtained in terms of dimensionless parameters, h√A_p/k and h_e/h. They are presented in graphical forms in order to aid thermal designers     

Construction and performance characteristics of a metformin electrode based on the metformin phosphotungstate ion-associate

A new metformin (Mf) ion selective PVC membrane electrode based on the ion-associate of Mf with phosphotungstic acid was prepared. The electrode exhibited a mean calibration graph slope of 58 mV Mf concentration decade^?1, at 25°C, within the concentration range 2·0 × 10^?5?1·0 × 10^?2 M MfCl. The change of pH within the range 4·0–11·0 did not affect the electrode performance. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficient of the electrode (0.000352 V°C^?1). The electrode showed a very good selectivity for Mf with respect to a large number of inorganic and organic cations. The standard addition method and potentiometric titration were applied to determine Mf in pure solutions and in metformin-containing tablets.     

Investigation of the filtration rate of silica in aluminum fluoride production from silicic acid

The effect of some influencing parameters such as temperature, initial concentration of flusilicic acid, rate of addition of Al(OH)₃ powder, agitation speed and aging time of slurry and their mixed effects on the filtration rate of silica precipitates have been investigated. Moreover, a suitable model is presented to describe the formation mechanism of aggregated silica precipitates which can well explain the effect of different factors on the filtration rate of the silica precipitates.