Multicomponent frequency shifting self-aligning laser velocimeters.
A design using simple lenses and frequency shift by scattering disk has been developed, which allows easy construction, and alignment of one-, two-, and three-orthogonal-component, frequency shifting laser Doppler velocimeters. A series of instruments designed on this basis have proved to be inexpensive to construct, precise and accurate to use, adaptable to a wide range of applications, and have proven particularly advantageous in studies of turbulent phenomena and complex flows. In this paper the design concept is explained, construction and alignment procedures are outlined for the simplest assembly of the one and two component versions, and performance and application examples are presented. The extension of the system to measure the third orthogonal component is discussed.
An autodyne frequency tracker for laser Doppler anemometry
A frequency tracker has been developed that produces a running average omega av of the frequency omega s of the laser doppler signal which is weighed according to the relation omega av=a2 omega s/a2, where a is the signal amplitude. It is shown that this mode of processing most effectively averages noise and ambiguity fluctuations. A practical system is described which operates at a Doppler frequency of up to 10 MHz. Measurements support predictions of response time (2 mu s at 1 MHz), accuracy and response to noise and ambiguity fluctuations. Measured long term accuracy is 0.2%.
Using Activity Theory in Developing Instructial Tools for Project Management Studies
Competence and skills of the project manager are significant to project success. The skills needed in project managersâ work cannot be learned only by reading the books or a lecture hall; one learns them by practice. Therefore, an important challenge for educational institutions is to develop pedagogical practices that allow students to participate in working life projects and to confront real-life problems. Project-based learning (PBL) offers a model that enables students to practice the skills and competences needed in working life projects by utilizing real-world work assignments in time-limited projects. Using PBL method alone does not necessarily guarantee learning result. In order to be successful, PBL method requires effective and competent supervision and guidance of students as well as appropriate tools for instruction. In this study the concepts from activity theory (AT) are applied to development tools for supervising project-based learning.