1,720,958 research outputs found
Core Temperature Measurement Using Ultrasound for High Precision Manufacturing Processes
Full text linkCORE TEMPERATURE MEASUREMENT USING ULTRASOUND FOR HIGH PRECISION MANUFACTURING PROCESSES
Full text linkDuring manufacturing processes, workpiece temperature may vary due to factors arising from the process such as tool/workpiece friction. Workpiece temperature may also vary due to the environmental conditions and these variations can affect the dimensional accuracy of the manufactured workpiece. The surface temperature of a part being manufactured can vary significantly from the core temperature, especially during dry cutting processes or when the environmental conditions are changing rapidly. It is known that the expansion of a part is controlled by its average temperature and can be influenced more by the core temperature of the part than the surface temperature due to the relative material volumes. Therefore, to effectively control or compensate for the effects of temperature variation as it relates to material expansion, there is a need to measure the core temperature of the workpiece accurately. Due to the harsh nature of many manufacturing environments, the required accuracy and resolution for temperature measurement in precision manufacturing are rarely achieved.
The aim of this research is to measure core temperature of workpieces during manufacturing processes with accuracy and resolution based on industry requirements. The main research objectives include simulating the chosen temperature measurement method to determine its suitability, designing a system for core temperature measurement, and using the designed system for core temperature measurement during a manufacturing process.
In this thesis, after reviewing the different temperature measurement methods with greater emphasis on those applicable to the manufacturing process, the ultrasonic thermometry was chosen for further study. The speed of sound in any medium depends on the temperature of the medium. Hence, if the length and time of travel of an ultrasonic wave can be measured, the speed, and consequently the temperature, can be measured. Since the ultrasonic method gives the average of the travel path, the core temperature can be obtained.
To verify these theories and determine the cost-effective technique of ultrasonic measurement for the present task, the MATLAB k-Wave toolbox was used for simulating the two main techniques of ultrasonic measurement – the pulse-echo and phase-shift methods. Using steel as the medium of propagation, the simulation results showed that both techniques can be used for the present task. However, further analysis of the results showed that the phase-shift technique could be the cost-effective option. Therefore, the phase-shift technique was chosen for the bench tests. Controlled heating of a steel test part was performed using a liquid bath calibrator and a reference temperature sensor for accurate comparison. The results showed that the measured temperature values using the phase-shift ultrasonic method agree with the reference PT100 measurements with the required resolution and accuracy. The phase-shift card used in this method is a cost-effective solution that eliminates the need for the expensive pulser-receivers used for the ultrasonic pulse-echo method.
Thereafter, the setup was used on a computer numeric control machine while incrementally introducing different levels of uncertainty to the manufacturing process. The results show that the phase-shift ultrasonic thermometry method measures workpiece temperature during subtractive manufacturing processes with accuracy of ±1 ℃. The setup was also used on a coordinate measuring machine during dimensional inspection. This test was set up to compare the calculated expansion based on core and surface temperature measurements with the measured expansion. The results show that the surface temperature-based expansion error is approximately 0.5 µm more than that of the core temperature. Finally, the created setup was used on an aluminium workpiece. The temperature measurement has error values within ±0.45 ℃ when compared with the reference PT100 readings with standard deviation of 0.1 ℃.
This is the first time that ultrasonic thermometry has been used to measure temperature of metal components being machined and is a novel solution to the significant challenges of part temperature measurement during machining
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Ultrasonic Thermometry for Manufacturing Materials Using the Pulse-Echo Method
No full textCore temperature of workpieces during manufacturing processes can vary significantly from the surface temperature. If the thermally induced expansion of the workpiece is estimated using the surface temperature, it may lead to a wrong estimation resulting in over or under-compensation for the effects of thermal expansion. Ultrasonic thermometry has been shown to measure the core temperature of steel sample of 100 mm (EN24T) with a resolution and accuracy of better than 0.5 °C and ±1 °C[1]. This study establishes the suitability of ultrasonic thermometry for other metals namely brass, stainless steel, aluminium, and mild steel. By using a calibrated temperature bath, the ultrasonic time-of-flight for different metals was measured. This was done to establish the relationship between the materials and the ultrasonic time-of-flight (TOF) in them at different temperature. The model that will be created using this measurement method can be used during dimensional inspection or subtractive manufacturing processes to aid the control or compensation for the effects of temperature change
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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