A comparison of lightness contrast effects in CRT and surface colours

The simultaneous contrast effect is investigated in this article. A total of 174 and 154 test/induction combinations were studied for CRT and surface colours respectively. Each combination was assessed by nine observers using a matching technique. The test and induction colours used for CRT colours were similar to surface colours using fabric samples. The results indicated a strong lightness contrast effect for both CRT and surface media; that is, the lightness of a test colour surrounded by a lighter induction colour was reduced for both CRT and surface colours. However, the effect in CRT medium was more pronounced than in the surface medium. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 13–20, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20074     

Assessment of service exposed boiler tubes

Boiler tubes in power plants have finite life because of prolonged exposure to high temperature, stress and aggressive environment. Service-exposed platen superheater and reheater tubes (148,900 h) made of 2.25Cr-1 Mo steels in a 120 MW boiler of a thermal power plant were evaluated for remnant life. The investigation included hot tensile tests, hardness measurement, dimensional measurement, microscopy and creep tests. Experimentally determined yield and ultimate tensile strength, and estimated 10,000–100,000 h rupture strength in the temperature range 520–580 °C, exhibited a decreasing trend with increasing temperature. Microstructural study did not reveal any significant degradation in terms of creep cavities, cracks, graphitization, etc. Analysis of tensile and stress rupture data revealed that although there was degradation of the tubes due to prolonged service exposure in terms of the ultimate tensile strength values, stress rupture plots showed that the service exposed superheater and reheater tubes could remain in service for a length of more than 10 years at the operating hoop stress of 40 MPa/540 °C, provided no localised damage in the form of cracks or dents develop.     

The schnittaxiom and unions of fuzzy subgroups

A necessary and sufficient condition for the union of an arbitrary family of fuzzy subgroups of a group to be a fuzzy group has been proposed. The criterion which gives a cut of the unit interval is called the Schnittaxiom. It has been applied successfully to investigate fuzzy subgroupness of arbitrary unions of homomorphic images and preimages.     

Parkinson's disease in populations of African origin: a review

Several studies have reported a lower prevalence of Parkinson's disease (PD) in populations of African origin than in populations of European origin, raising the possibility that the former are protected against PD. However, the confounding effects of low case ascertainment and high selective mortality on PD prevalence estimates in populations of African origin cannot be ruled out at this time. One hypothesis consistent with available data is that populations of African origin are vulnerable to vascular parkinsonism, which is associated with high mortality.     

Modelling of addition polymerization processes — Free radical,ionic, group transfer,and ziegler–natta kinetics

A brief review of addition polymerization processes is presented with a summary of the key characteristics classified by kinetic mechanism (free-radical, anionic, cationic, group transfer, or Ziegler–Natta), phase behavior, and reactor type. A practical approach to modelling in the industrial R & D environment is discussed in terms of a CAD package for polymerization processes.     

Bidirectional calibration results for 11 spectralon and 16 BaSO4 reference reflectance panels

Eleven Spectralon¹ (a sintered polytetrafluoroethylene-based material) and 16 BaSO₄ reference reflectance panels were calibrated using a field calibration technique. The Spectralon panels differed both in their directional/hemispherical and directional/directional reflectance. However, the differences were sufficiently small that “general” calibration equations were developed. For panels constructed of the same material and with the same methods as those used in these experiments, the directional/directional reflectance may be within ± 0.020 at 10°, ± 0.015 at 45°, and ± 0.041 at 80° of that predicted by the “general” equations. For field measurements, these values are considerably better than those that would be obtained using a value of the directional/hemispherical reflectance. The directional/directional reflectance of the 16 BaSO₄ panels varied considerably among panels, so much so that it was not feasible to develop “general” calibration equations. Apparently, the nonlambertian properties of BaSO₄ panels are dependent upon the method of applying the barium sulfate coating.     

Cost optimization of maintenance scheduling for a system withassured reliability

Systems which have to work at or below a maximum acceptable failure rate should be maintained at predetermined points such that the failure rate does not exceed the acceptable level. As the system ages, the post-maintenance failure rate of the system drops to some newer one, unless the system has been replaced, but does not restore the system to the original state. A branching algorithm with effective dominance rules that curtail the number of nodes created is presented; this algorithm determines the number of maintenance interventions before each replacement in order to minimize the total cost over a finite time horizon. The model considers inflationary trends. A numerical example and computational experience are presented. The authors treat the maintenance cost as constant and successive simple-maintenance intervals as decreasing. Though the cost/maintenance is assumed constant, any increasing maintenance cost function could be incorporated. The optimum solutions depend on the constant improvement factor, first simple-maintenance point, rate of increase in acquisition cost, maintenance cost factor, and planning period