Steady viscous flow past a tapered cylinder

The three-dimensional nature of the viscous flow past a linearly tapered circular cylinder is examined at low Reynolds numbers. The numerical solution of the unsteady Navier–Stokes equations converges to a steady state. The primary flow in planes perpendicular to the cylinder axis is practically indistinguishable from the two-dimensional flow past a uniform cylinder. A secondary spanwise flow is observed in the stagnation zone going from the wide end towards the narrow end, whereas a secondary motion on the rear side goes in the opposite direction. In spite of this secondary flow, the length of the separation zone varies linearly with the local Reynolds number.     

Fluorescence method for monitoring isothermal curing and shelf life of an epoxy–anhydride system

A fluorescence technique with seven fluorescent probes was applied to monitor the curing and shelf life of an epoxy resin. As isothermal curing proceeded, the fluorescence emission bands of the probes exhibited blue shifts because of microviscosity and micropolarity changes. An intensity ratio method was applied in which ratios of the lowest and highest intensity changes in the emission bands were used to determine the degree of isothermal curing. A smooth and, in some cases, a linear correlation was found between the fluorescence intensity ratio and the degree of cure. This method enables the degree of cure to be monitored and allows comparable results from different types of probes to be monitored during the same curing process. The fluorescence technique and the ratio method offer the possibility of monitoring the precuring and the shelf life of the epoxy polymer. The method can be used to compare the kinetics of various monomers and resin formulations under constant curing conditions. Thus, the method would be useful for developing new resin formulations and technologies and could be applied to a variety of commercial and industrial uses of epoxy resins. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2607–2615, 2001     

Interactions of Na2SO4 and yttrium-silicate environmental barrier coatings at 825°C

Yttrium-silicates (Y₂Si₂O₇ and Y₂SiO₅) are candidate environmental barrier coating (EBC) materials for silicon carbide ceramic matrix composites (SiC-CMCs). These materials’ high-temperature, high-velocity steam, and siliceous debris resistance are well studied. However, Na₂SO₄-induced hot corrosion mechanisms are less understood. Free-standing atmospheric plasma sprayed Y₂Si₂O₇ and Y₂SiO₅ coupons were exposed to 2.5 mg/cm² of Na₂SO₄ at 825°C in 0.1% SO₂-O₂ (g). Scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and inductively coupled plasma-optical emission spectrometry were used to identify a previously unknown damage mechanism. Water-soluble Y and Na-Y sulfates and oxysulfates formed in reaction with Na₂SO₄, causing significant damage to the yttrium-silicate EBCs materials.     

The function of ability,benevolence, and integrity-based trust in innovation networks

ABSTRACT

This study contributes to the understanding of how trust based on perceived ability, benevolence, and integrity functions in networks. It adopts a mixed-method approach with quantitative and qualitative data from five Norwegian innovation networks. The study demonstrates how trust based on perceived benevolence, ability, and integrity influences different aspects of network interaction and network outcomes against the background of the network members’ perceptions of risk. Moreover, it finds that these dimensions of trust function differently at the inter-organisational and at the network level. The former level here concerns trust between the organisations in the network, while the latter concerns trust in the network more generally. Benevolence-based trust is identified as particularly salient at both levels for promoting open and honest communication as well as knowledge sharing, enabling both more successful collaboration in general, and more innovation specifically.     

An immunoassay to evaluate human/environmental exposure to the antimicrobial triclocarban

A sensitive, competitive indirect enzyme-linked immunosorbent assay (ELISA) for the detection of the antimicrobial triclocarban (TCC) was developed. The haptens were synthesized by derivatizing the para position of a phenyl moiety of TCC. The rabbit antisera were screened and the combination of antiserum 1648 and a heterologous competitive hapten containing a piperidine was further characterized. The IC(50) and detection range for TCC in buffer were 0.70 and 0.13-3.60 ng/mL, respectively. The assay was selective for TCC, providing only low cross-reactivity to TCC-related compounds and its major metabolites except for the closely related antimicrobial 3-trifluoromethyl-4,4'-dichlorocarbanilide. A liquid-liquid extraction for sample preparation of human body fluids resulted in an assay that measured low part per billion levels of TCC in small volumes of the samples. The limits of quantification of TCC were 5 ng/mL in blood/serum and 10 ng/mL in urine, respectively. TCC in human urine was largely the N- or N'-glucuronide. TCC concentrations of biosolids measured by the ELISA were similar to those determined by LC-MS/MS. This immunoassay can be used as a rapid, inexpensive, and convenient tool to aid researchers monitoring human/environmental exposure to TCC to better understand the health effects.     

Structural health monitoring of cylindrical structures using guided ultrasonic waves

The research field of structural health monitoring (SHM) in the realm of civil engineering has emerged rapidly. SHM concepts are based on integrated sensors and actuators to evaluate the structural state. Beside common structural response methods and other nondestructive testing techniques, wave-based ultrasonic techniques are widely used especially because of their flexibility. Monitoring cable structures such as overhead transmission lines or stay cables in suspension bridges is one objective of those wave-based methods. These structures are subject to aging, corrosion and other static and dynamic loads (e.g., wind, temperature). The cylindrical structures act as waveguides whereby monitoring of large distances with a single ultrasonic transducer is possible. However, the wave propagation is multimodal and dispersive, which complicates analysis of the wave motion and development of monitoring applications. This work addresses several aspects of the propagation of guided waves in cylinders, especially the analysis of reflection and transmission at discontinuities using finite element and boundary element methods.