Inversion of refraction data by wave field continuation

The process of wave equation continuation (migration) is adapted for refraction data in order to produce velocity-depth models directly from the recorded data. The procedure consists of two linear transformations: a slant stack of the data produces a wave field in the p - τ plane which is then downward continued using τ = O as the imaging condition. The result is that the data wave field is linearly transformed from the time-distance domain into the slowness-depth domain, where the velocity profile can be picked directly. No travel-time picking is involved, and all the data are present throughout the inversion. The method is iterative because it is necessary to specify a velocity function for the continuation. The solution produced by a given iteration is used as the continuation velocity function for the next step. Convergence is determined when the output wave field images the same velocity-depth function as was input to the continuation. The method obviates the problems associated with determining the envelope of solutions that are consistent with the observations, since the time resolution in the data is transformed into a depth resolution in the slowness-depth domain. The method is illustrated with several synthetic examples, and with a refraction line recorded in the Imperial Valley, California

Connecting Best Practices for Teaching Linguistically and Culturally Diverse International Students with International Student Satisfaction and Student Perceptions of Student Learning

This paper explores promising teaching practices for teaching linguistically and culturally-diverse international students by identifying the teaching practices that have high levels of international student satisfaction and student perceptions of learning. This study is based on the belief that the most effective teaching practices are where promising teaching practices, student satisfaction, and student perceptions of learning meet. Researchers used a mixed-methods research design that included an online-survey questionnaire, focus-group discussions, and individual interviews. All of the promising teaching practices identified as having high levels of student satisfaction have medium/high perceptions of student learning. Some of the promising teaching practices with high levels of student perceptions of learning have moderate levels of student satisfaction. Recommendations for professional practice are presented along with potential areas for further research

Cavallo's Multiplier for in situ Generation of High Voltage

A classic electrostatic induction machine, Cavallo's multiplier, is suggested for in situ production of very high voltage in cryogenic environments. The device is suitable for generating a large electrostatic field under conditions of very small load current. Operation of the Cavallo multiplier is analyzed, with quantitative description in terms of mutual capacitances between electrodes in the system. A demonstration apparatus was constructed, and measured voltages are compared to predictions based on measured capacitances in the system. The simplicity of the Cavallo multiplier makes it amenable to electrostatic analysis using finite element software, and electrode shapes can be optimized to take advantage of a high dielectric strength medium such as liquid helium. A design study is presented for a Cavallo multiplier in a large-scale, cryogenic experiment to measure the neutron electric dipole moment.Comment: 9 pages, 10 figure

Variability by Individual Student Characteristics of Student Satisfaction with Promising International Student Teaching Practices

This paper explores promising teaching practices for teaching linguistically and culturally diverse international students by identifying the teaching practices that have high levels of international student satisfaction and student perceptions of learning. Data were collected through an online survey at a mid-sized Canadian public comprehensive university. Variability of student satisfaction by individual student characteristics (e.g., level of study, year of study, age, gender, field of study, country of origin, length of time studying outside country of origin, parents’ educational level, and study location) is presented. Recommendations for professional practice are discusse

Application of Wave Field Continuation to the Inversion of Refraction Data

Three examples of the inversion of refraction data by downward continuation illustrate the applicability of the method to field data. The first example is a refraction profile from the Mojave Desert, California. These data are spatially aliased and contain clear evidence of lateral inhomogeneity. The inversion in this case produces a broken image in the slowness-depth domain due to the lateral inhomogeneity, but a useful average velocity model is still obtained. The second example is a shallow marine reflection profile. Here, the truncation effects due to the finite horizontal aperture of the recording cable produce artifacts in the slowness-depth domain. The velocity model is, however, distinct from these artifacts, and the presence of strong precritical reflections aids in the inversion. The third example is another shallow marine reflection profile. The inversion of these data illustrate the utilization of constraints provided by multiples as well as primary arrivals

Sustainability appraisal: Jack of all trades, master of none?

Sustainable development is a commonly quoted goal for decision making and supports a large number of other discourses. Sustainability appraisal has a stated goal of supporting decision making for sustainable development. We suggest that the inherent flexibility of sustainability appraisal facilitates outcomes that often do not adhere to the three goals enshrined in most definitions of sustainable development: economic growth, environmental protection and enhancement, and the wellbeing of the human population. Current practice is for sustainable development to be disenfranchised through the interpretation of sustainability, whereby the best alternative is good enough even when unsustainable. Practitioners must carefully and transparently review the frameworks applied during sustainability appraisal to ensure that outcomes will meet the three goals, rather than focusing on a discourse that emphasises one or more goals at the expense of the other(s)

A Subsumption Agent for Collaborative Free Improvisation

This paper discusses the design and evaluation of an artificial agent for collaborative musical free improvisation. The agent provides a means to investigate the underpinnings of improvisational interaction. In connection with this general goal, the system is also used here to explore the implementation of a collaborative musical agent using a specific robotics architecture, Subsumption. The architecture of the system is explained, and its evaluation in an empirical study with expert improvisors is discussed. A follow-up study using a second iteration of the system is also presented. The system design and connected studies bring together Subsumption robotics, ecological psychology, and musical improvisation, and contribute to an empirical grounding of an ecological theory of improvisation