Final Design of Secondary Refrigeration System and Wind Tunnel

The goal of the secondary refrigeration system project was to design and build a secondary refrigeration loop to interface with an existing primary refrigeration loop for the testing and research of microencapsulated phase change material, as well as an educational tool for students interested in refrigeration. The aim of this report is to discuss and explain the final version of the design, the testing methods, results, conclusion, and any future recommendations. The wind tunnel is operational, reaching an average maximum air velocity close to what the group had aimed for. The heaters were able to heat the air to the desired range. Piping and most components and instrumentation have been connected and mounted. LabVIEW has been set up to read the outputs of the instruments. Unfortunately, the steam generator has not been mounted and the system has not been charged due to time constraints. Since much time was spent fixing the primary loop to an operational state, it is recommended that future groups working on the existing refrigeration loops ensure that they are working prior to the start of a new project. Overall, the client who requested this system is satisfied with the outcome, despite not meeting certain design criteria

A robust sequential hypothesis testing method for brake squeal localisation

This contribution deals with the in situ detection and localisation of brake squeal in an automobile. As brake squeal is emitted from regions known a priori, i.e., near the wheels, the localisation is treated as a hypothesis testing problem. Distributed microphone arrays, situated under the automobile, are used to capture the directional properties of the sound field generated by a squealing brake. The spatial characteristics of the sampled sound field is then used to formulate the hypothesis tests. However, in contrast to standard hypothesis testing approaches of this kind, the propagation environment is complex and time-varying. Coupled with inaccuracies in the knowledge of the sensor and source positions as well as sensor gain mismatches, modelling the sound field is difficult and standard approaches fail in this case. A previously proposed approach implicitly tried to account for such incomplete system knowledge and was based on ad hoc likelihood formulations. The current paper builds upon this approach and proposes a second approach, based on more solid theoretical foundations, that can systematically account for the model uncertainties. Results from tests in a real setting show that the proposed approach is more consistent than the prior state-of-the-art. In both approaches, the tasks of detection and localisation are decoupled for complexity reasons. The localisation (hypothesis testing) is subject to a prior detection of brake squeal and identification of the squeal frequencies. The approaches used for the detection and identification of squeal frequencies are also presented. The paper, further, briefly addresses some practical issues related to array design and placement. (C) 2019 Author(s)

Sinkhole Distribution Based on Pre-Development Mapping in Urbanized Pinellas County, Florida, USA

Locating sinkholes in Pinellas County, Florida, is confounded by the presence of a cover of Quaternary sediments that mute the surface appearance of these sinkholes. As a first step in addressing the sinkhole hazard in the county, we analysed aerial photographs from 1926 and 1995 that covered the entire county. We digitized all identifiable sinkholes in each set of photographs in a GIS (Geographical Information System) using a set of criteria established to differentiate between karst depressions and depressions resulting from other geological processes. The 1926 photographs, although of low quality, helped to establish a baseline prior to urbanization. The 1995 photographs provided a post-urbanization distribution of natural sinkholes and man-made depression features (e.g. retention ponds). From these two data sets, we are able to assess natural and anthropogenic changes in the karst landscape of the study area. In particular, we discovered that 87% of the sinkhole features identified in the 1926 photographs are no longer present in the photographs from 1995. Many of the lost depressions have been incorporated into retention ponds