It is argued that because of the lack of intrinsic length and time scales in the core part of the jet flow, the radiated noise spectrum of a high-speed

No abstract

The lowermost section of a Vulcanian or Plinian volcanic eruption column may be thought of as a momentum‐driven, turbulent, free‐shear jet flow. We propose that large‐amplitude and long‐duration infrasonic (<20 Hz) signals recorded at ranges of tens of kilometers during powerful eruptions at Mount St. Helens, USA, and Tungurahua, Ecuador, represent a low frequency form of jet noise. A preliminary test of this hypothesis is made by comparing the observed infrasonic spectra to the empirically‐derived similarity spectra for pure‐air jets. Although the spectral shapes are in approximate agreement, the observed volcanic signals have additional complexities not present in the pure‐air laboratory data. These features may result from multiphase flow containing solid particles and liquid droplets, very high temperatures, and perhaps complex crater morphology. However, the overall similarity between the volcanic signals and jet noise indicates that broadband infrasound measurements at volcanoes may provide a quantitative link to eruption jet dynamics, and would aid substantially in the remote assessment of volcanic hazard.

The engineering professor's role is dualistic in the sense that not only must s/he create an academic environment conducive to the acquisition of course content but must also prepare students to become practicing professionals. This dualism requires that the professor both motivate good study habits as well as build within students the confidence that they have the requisite capability to perform actual engineering. Self-efficacy, simply defined as one's self-judgment concerning capability, has been shown to be an important mediating factor in cognitive motivation. This paper describes the motivating role of the professor, theories of motivation, the role of self-efficacy in motivation, and guiding principles that can be used to enhance self-efficacy in engineering students. These principles can serve as guidelines in designing instructional delivery strategies that motivate engineering students to engage in behaviors conducive to becoming value-added practitioners.

No abstract