Senior project or Capstone‐type courses have existed at engineering schools for many years. Capstone courses provide student engineers the opportunity to solve real‐world engineering projects, and have been highly regarded as important learning activities. A survey of Capstone courses in engineering departments throughout North America was conducted in order to understand current practices in Capstone education. This study was conducted for presentation at the 1994 Advances in Capstone Education Conference, held at Brigham Young University, which brought together engineering educators interested in improving Capstone experiences. This conference was sponsored by ASEE, ASME, SME, and NSF. Response to the study was very high, with 360 departments from 173 schools responding to the survey. Survey results were categorized into five major areas of interest: Profile of the Respondents, Course Description Information, Faculty Involvement in Capstone Education, Project Information, and Industrial Involvement in Capstone Education. Graphs provide the results of responses to survey questions.

A theoretical and experimental study of a proposed hybrid passive–active plane-wave system to provide broadband acoustic absorption is presented. The passive absorber consists of a microperforated panel (MPP), used in place of conventional fibrous materials, in front of an air layer. The active system uses an active transducer (a loudspeaker), an error sensor (a microphone), and an adaptive controller. MPPs are thinner than fibrous materials and provide a better solution in hygienic environments. For two such systems, the dependence of performance on MPP parameters is studied for two control strategies: impedance matching and pressure release. The first condition is found to be better for cases where the acoustic impedance of the system approaches that of air. Otherwise, the pressure-release condition is better, and a wideband solution is the implementation of the active control system up to a frequency where the natural band of the passive system provides higher absorption. Therefore, the use of a low-pass filter in the error signal is implemented to afford hybrid passive–active wideband absorption. The control effort of active system is also considered. Experimental verification shows good agreement with theory, and an average absorption coefficient of 0.82 in the frequency bandwidth 100 to 1600 Hz was achieved.

A two-dimensional lightweight cantilever structure is studied, comprising 40 rigidly joined beams, of which the geometry is optimized to reduce vibration transmission over a given bandwidth. In this paper, the optimization is achieved by using genetic algorithms. Ten optimized design candidates were achieved for each of three cases resulting from minimizing an objective function (the vibration transmission between two points on the structure) which is calculated (i) using a single frequency, (ii) the frequency average over a narrow bandwidth, and (iii) the frequency average over a broad frequency range. All the candidates show performance improvements and normally the best performance is taken to be the best candidate. This paper then considers the sensitivity of each optimal candidate to small changes in the geometry of the structure. If the performance of a structure is too sensitive to perturbations its practical application is limited or may not be realizable in practice. The robustness of the optimized candidates is studied in order to "nd those candidates which are least sensitive to changing design parameters. This is achieved by perturbing the positions of the joints by an ensemble of sets of random numbers. The statistical e!ect on the objective function is investigated, and some candidates are seen to be more robust to such perturbations than others and generally the greater the bandwidth over which the structure is optimized the more robust the design. A selection criterion is then applied which enables the best candidates to be identi"ed on grounds of both nominal optimized performance and robustness. Finally, the advantage of using genetic algorithms over traditional &&hill-climbing'' optimization methods is shown, on the grounds of both nominal performance and robustness.

A technique is described and demonstrated for generating high-resolution 3-D images of the objects on the seabed, combining synthetic aperture sonar with bathymetric (interferometric) processing. This has applications in surveying of oil wells, pipelines and shipwrecks, and in defence in mine hunting. It is shown that the technique is very sensitive to platform motion errors, and ways are discussed by which the errors may be estimated and compensated. Practical results obtained with an experimental system in a test tank are presented and discussed, and a number of areas for further work are identified. 1 Introduction Sidescan sonars are now a widely accepted and important tool of ocean technology. Broadly, they fall into one of two classes: the short-range high-resolution systems working at a relatively high frequency (e.g. about 100kHz), and the long-range low-resolution systems working at 10kHz or less. The former have a wide range of applications in surveying of oil wells, pipelines and shipwrecks, and in defence in mine-hunting. The longer range systems such as GLORIA have contributed significantly to the study of the deep ocean floor. The original method of determining seabed topography is by means of an ship-mounted echo sounder, covering a given area in a raster fashion. This is slow

Abstract:The accuracy of modal frequency and damping estimators for non-lightly damped single degree of freedom systems depend on the response parameter used as well as the damping mechanism. Therefore, in order to make accurate modal parameter measurements, the damping mechanism at play must be known to be either viscous or hysteretic a priori. Here, comparisons between the evaluated frequency values are used to glean this information. The damping mechanism of an experimental system (consisting of resilient layer and mass plate) is then determined using two simple modal parameter estimators and applying statistical methods.

In this paper, results for active vibration control predicted from experimental measurements on a lightweight structure are compared with purely computational predictions. The structure studied is a 4.5 m long satellite boom consisting of 10 identical bays with equilateral triangular cross sections. First, the results from a Fortran code that is based on a receptance analysis are validated against the experimental forced response of the boom structure. Exhaustive searches are then carried out to find the optimum positions for one and two actuators. Finally, a genetic algorithm is employed to find high-quality positions for three actuators on the structure that will achieve the greatest reductions in vibration transmission. Having found these actuator positions, experiments are then carried out to verify the quality of the theoretical predictions. It was found that the attenuation achievable in practice for one, two and three actuators were, respectively, 15.1, 26.1 and 33.5 dB.

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