Evaluation of Loss Factor Estimation Techniques for Free Hanging Flat Panels Excited Mechanically

To establish the "best" technique to estimate a damping loss factor for mechanically-excited panels, three loss factor estimation techniques--PIM, IRDM, and RDT--are compared. In experimental and computational analyses, panels with two damping levels and three sizes were tested. The loss factor estimates from each of the three techniques are then evaluated in four distinct frequency bands centered at one-third octave frequencies of 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz (for computational analysis only). Unlike IRDM and RDT, the quality of PIM-based loss factor estimates have presented a strong correlation between the region of response measurement and it is distance from the excitation location. PIM-based loss factors were significantly underestimated when responses are measured inside the direct field. PIM-based loss factors are relatively accurate only if the measurements are made from wide-spread response locations. For a lightly damped panel, loss factor estimates using PIM, IRDM and RDT with direct averaging agree within reasonable accuracy. For intermediately to highly damped panels, IRDM and RDT with direct averaging under-predicted the loss factor; RDT with an autocorrelation function averaging approach slightly over-predicted the loss factor. Both RDT approaches might be used to set a bound on panel loss factor. Even when significantly fewer response locations are considered, it is evident that loss factor estimates from RDT are as reliable as IRDM and more reliable than PIM especially for highly damped panels. For the analysis of freely hanging plates, excitation "close to an edge", especially for PIM, is not recommended. When analyzing the panel loss factor, arbitrary or central excitation is acceptable

Panel Damping Loss Factor Estimation Using The Random Decrement Technique

The use of the Random Decrement Technique (RDT) for estimating panel damping loss factors ranging from 1% to 10% is examined in a systematic way, with a focus on establishing the various parameters one must specify to use the technique to the best advantage. Throughout, loss factors are estimated in full or 1/3rd octave frequency bands with standard 1/3rd octave center frequencies. The full octave filters, which are more computationally efficient than the 1/3rd octave filters, are chosen in the experimental analysis of the damped plates with varied loss factor levels. Two computational models are examined: a single degree of freedom oscillator and a computational model of a uniform rectangular panel. The panel computational model is a finite element model of a rectangular plate mechanically exited at a single point. These models are used to establish a systematic process for evaluating: the appropriate narrow band filter selection; trigger conditions; record length required as a function of frequency and damping level; the averaging scheme; and, the curve-fitting scheme for assigning loss factors in narrow frequency bands. Loss factor estimates for three damped plates are computed using the "optimized" Random Decrement estimation algorithm and compared with estimates from the Impulse Response Decay Method. For the highly damped plates, RDT out-performed IRDM because the loss factors from IRDM are underestimated. For lightly damped plates, RDT and IRDM are consistent in most frequency bands

Hypoglycaemic Activity of Centella Asiatica (L) Urb

The water extract of whole plant of Centella asiatica is used by traditional healers in the Haya tribe in Bukoba Region in Tanzania, in the management of both insulin and non-insulin dependent diabetes mellitus. Centella asiatica administered orally at a dose of 2 g/kg and 4 g/kg body weight produced a significant hypoglycaemic activity (

Simulation of Multiprocessor System Scheduling

The speed and performance of computers have become a major concern today. Multiprocessor systems are introduced to share the work load between the processors. By sharing the work load among processors, the speed and efficiency of the system can be increased drastically. To share the workload properly between the processors in the multiprocessor system a proper scheduling algorithm is needed. Hence, one of the major factors that influence the speed and efficiency of the multiprocessor system is scheduling. In this thesis, the main focus is on the process scheduling for multiprocessor systems. The factors which influence scheduling and scheduling algorithms are discussed. Based on this idea of sharing the load among processors in the multiprocessor system, a simulation model for scheduling in a symmetric multiprocessor system is developed in the Department of Digital and Computer systems at Tampere University of Technology. This model treats all the processors in the system equally by allocating equal processor time for all the processes in the task and also evaluates the total execution time of the system for processing an input job. The scheduling algorithm in this simulation model is based on the input processes priority. The necessity of scheduling in multiprocessor systems is elaborated. The goal of this thesis is to analyse how process scheduling influences the speed of the multiprocessor system. Also, the difference in total execution time of the input jobs with different number of processors and capacity of the processors in the multiprocessor system is studied

Characterization of brain signals using the electroencephalagogram during the stroop test

The study of mental stress is essential to elevate our understanding of the designer's cognitive approach during a creative design process. As the first step in this effort, this thesis focuses on the analysis of the electroencephalogram (EEG) signals of the subject during the stroop test. Computer based stroop test, consisting of six difficulty levels, was developed and used as a stressor. The EEG data was recorded on Fz, Cz, Pz and Oz channel locations. Average absolute power of alpha, beta, delta and theta bands at all the channel locations was calculated. The subject's average performance on the Stroop test was calculated based on his/her reaction time and incorrectness. It was observed that the power of theta band is more dominant in the Fz channel. Since the theta band corresponds to the subject's mental/emotional stress, the present study suggests using the theta band in Fz location for further analysis during the design process. It was also observed that Alpha and beta powers, corresponding to the subject's vision, are more dominant in the Oz channel. A simultaneous comparison of the performances and of the theta power of different subjects suggested a direct relationship between the performance and the theta power. The present study demonstrates the potential use of theta power, after being quantified in terms of mental/emotional stress, in obtaining a correlation between the subject's performance and mental/emotional stress. The present thesis laid a foundation for on-going analysis of designer's mental stresses during design related tasks, in Dr. Zeng's research group

Comparative Analysis of Abrasive Wear Using Response Surface Method and Artificial Neural Network

This research work deals with the application of response surface methodology and artificial neural network-based mathematical modelling of abrasive wear volume for a dry sliding wear of PTFE pin. The experiments were designed based on central composite design. The disc speed, load and sliding distance have been selected as parameters of the process, while the abrasive wear volume has been selected as an output. The ANNOVA test revealed that the disc speed has maximum influence and contributes 28.21% of abrasive wear volume followed by load, which contributes 12.83% of abrasive wear volume. The two models were compared using root mean square error and absolute standard deviation. The artificial neural network-predicted values of abrasive wear volume were found in close agreement with the actual experimental results as compared to response surface methodology predicted results and hence recommended for the similar studie

Site selection for solid waste management in Krishna district, Andhra Pradesh using GIS

Solid waste management involves collecting and processing garbage. It also recycles products. Solid waste management helps determine the best ways to use industrialised garbage. Industrialization produces chemicals and other waste products that harm human health. Solid waste management reduces this impact. Waste management has several ways. This study examined Krishna district in Andhra Pradesh. This study collects soil and geological data. This study shows how GIS may be utilised for waste management planning. The result shows the solid waste management area. So, garbage management should be simplified

Phylogenetic and Functional Diversity of Faecal Microbiome of Pack Animals

The present chapter describes the microbial diversity of faecal microbiomes of pack animals. The sequencing data generated through ion semiconductor sequencing technology were analysed using EBI metagenomics and MG‐RAST server tools. Bacteria were the major domain in all the pack animals. At the phylogenetic level, Firmicutes was the major phylum. Clostridiales was the major order. Ruminococcus flavefaciens was the major species in camel, whereas the top‐most species existing in Equidae family was Streptococcus equinus. Among the 28 major functional categories, protein metabolism functionality was dominant in pack animals. The genes associated with protein processing and modification as well as for protein folding are higher in mules and in camel they are lowest. Central carbohydrate metabolism was the major functional group under carbohydrate metabolism in pack animals. Variation in the amino acids and its derivatives was seen in pack animals. Genes associated with proline and 4‐hydroxy prolines were present in Equidae family only. Clustering using ward with Bray‐Curtis distance matrix for the functional categories showed that donkey and mule are most closely related and clustered with the horse metagenome

History, politics and dogs in Zimbabwean literature, c.1975–2015

Zimbabwean fiction writers have engaged with dogs as objects, subjects and even actors. This essay focuses on the pivotal forty-year period between 1975 and 2015, which saw the end of white rule, the rise of an independent African state and the collapse of that state. In analysing how selected writers have variously made use of dogs, we discuss the extent to which writers deal with human-dog relations. We buttress our point by examining key pieces of fiction in which dogs appear and we unpack the extent to which fictive representations of humans and dogs approximate lived relations in pre-colonial, colonial and post-colonial settings. We show the enduring relevance of dogs as metaphors of power in the Zimbabwean political landscape. We contend that such canine allegories have a history and explore their usage by creative writers over the last forty years