1,720,964 research outputs found
Analysis and correction of errors in vertical CNC machine centers for precise machining of CK45 steel products using task specific calibration approach
Get PDFKalibrasyon, metrolojik izlenebilirliği olan ölçüm sonuçlarına göre, cihazların hata değerlerinin belirlenip, düzeltilmesine imkân tanıyarak, endüstriyel ihtiyaca göre arzu edilen toleranslarda cihazların çalışmasını sağlar. Bu çalışmada, endüstri 4.0 uygulamalarında öne çıkan sıfır hata konseptine göre Ck45 çeliğinin delinmesi sırasında, tezgah ilerleme mekanizmalarındaki sıcaklık artışına bağlı olarak delik eksenleri arasındaki mesafelerde meydana gelen sapma değerlerini azaltarak hassas işleme için düşük maliyetli kompanzasyon (telafi) metodu geliştirilmiştir. İlk olarak CNC takım tezgâhı, OKUMA marka Genos Seri M560R-V model 3 eksen CNC dik işleme merkezinin mevcut durumunu tespit etmek için performans testleri ISO-230 serisi standartlarına göre Lazer interferometre (HP5529A) yardımıyla gerçekleştirilmiştir. Tezgahın yoğun çalışması sırasında, eksen hareket mekanizmalarında oluşan sıcaklık artışı ile hareket milinin uzaması sonucu meydana gelen eksen pozisyon hataları mastar blokları ve tezgaha entegre ölçme probu yardımıyla ölçülmüştür. Mastar bloklarının tezgâh tablasına bağlantısında kinematik fikstür kullanılmıştır. Yeni yöntem sayesinde, delik delme esnasında oluşan pozisyon hataları tespit edilmiş ve referans mastar blokları yardımıyla doğrulama faktörü bulunmuştur. Bu faktör kullanılarak, hata miktarı oranında nümerik kontrol (NC) kodları güncellenmiştir. Elde edilen sonuçlara göre bu yöntemin düşük maliyet ile hassas parça imalatında kullanılabilir olduğu sonucuna varılmıştır. Ayrıca eş zamanlı olarak yapılan işlem ile kompanzasyon yapılabileceği tespit edilmiştir. Delik mesafesi 500 mm için 55 ?m olan tezgâhtan kaynaklanan pozisyon hatasının, yeni yöntemle ±10 µm tolerans aralığında gerçekleştiği sonucuna ulaşılmıştır. Yeni metot kullanarak ve kullanmadan delinen delikler arası mesafe ZEISS PRISMO-7 S-ACC marka koordinat ölçüm cihazı (CMM) kullanılarak ölçülmüştür. Deneylerde Ø17 mm çapında Kennametal marka karbür takma uçlu matkap kullanılmıştır. Uygulanan yeni kompanzasyon yöntemi yardımıyla eksen sapma değerleri %81 oranında iyileştirilmiştir.Calibration provides the devices with operation in the required tolerances by determining error compensation values using the metrologicaly traceable measurement results. In this experimental research, a low cost compensation method was developed for drilling of holes on a steel Ck45 work piece with better precision by reducing the distance error between the hole axes caused by thermal issues in the axis moving mechanisms of the machine tool. Initially, performance tests of the machine tool, (3 axis CNC Vertical Milling Machine - OKUMA Genos M560R-V) was carried out according ISO-230 series standard using a laser interferometer (HP5529A). The position error of the machine tool axis resulting from thermal expansion of lead screw due to temperature variations (occurring in intensive use) was measured using reference long gauge blocks and machine integrated Renishaw probing system. With application of the new method, the gauge blocks were arranged in line to the machine tool axis with specially designed kinematic fixture and provided us with reference distance values to determine the position errors of machine tool axis occurred during drilling operation. On-line correction factor was determined and used to revise the part dimensions in the CAD file. Two set of holes were drilled with original part dimensions and revised dimensions using a Kennametal Ø17 mm diameter carbide drilling tool. Both results were evaluated by measuring the distance of the holes using a precise coordinate measurement machine (CMM - ZEISS PRISMO-7 S-ACC) in the laboratory. Measurement results of the manufactured part produced using the original part programme and corrected part programme were compared to each other. Improvement was achieved reducing the 55 ?m error value (per 500 mm) down to be within ± 10 ?m. It was evaluated that the new method provided very practical and low cost solution for precise drilling of the holes as well as giving information for improving the integrated probing system measurements
A motorized 5 m tape comparator for traceable measurements of tapes and rules
No full textA motorized 5 m tape comparator was constructed in TUBITAK UME for calibration of tapes and rules up to 5 m length in one set-up and further lengths in multiple set-ups. The system is a practical development and provides a cost effective solution for calibration of tapes in which the highest grade's accuracy requirement in OIML R35-1 e.g. is 600 mu m for 5 m length and 1100 mu m for 10 m length. It is mainly composed of 6 m rail system, mechanical parts, optical units and an integrated 6 m incremental linear encoder as a reference measurement axis for traceable measurements. The rails are kinematically located on a heavy marble construction and a motorized carriage, which employs a camera for probing of the scales on the tapes, is moved along the rails during the measurement. The image of the scale taken by the camera is viewed on the monitor screen together with the running software. The operator can perform the probing process by simply moving the carriage over the measured scales (tapes or rules) using a joystick. The carriage movement is measured by the incremental linear encoder previously calibrated by a laser interferometer and the software automatically takes the measurement results from the incremental linear encoder, applies correction values previously defined and determines the length of the tapes and rules as well as deviations from nominal lengths. The estimated expanded uncertainty of the steel tape measurement is U = 54 mu m in one set-up (for 5 m length) and U = 77 mu m in two set-ups (for 10 m length) at the confidence level of approximately 95%. Uncertainty budget for calibration of the device itself and for calibration of the test tapes are explained in detail. The results of extensive experimental work and analysis are provided by demonstrating application of science and technology of measurement and instrumentation. Investigations for long term stability of the system are given with the reported test results for the years of 2003-2011 and participated intercomparison results to validate the device scientifically are illustrated. (C) 2013 Elsevier Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Traceability issues for contact probe and stylus instrument measurements
Get PDFSurface texture and form of products are important features to be examined and numerically characterised as parameters for engineering and scientific purposes. Form and surface measurement devices with contact probes and stylus are used to characterise such surfaces. Additionally, new generation Coordinate Measuring Machines (CMMs) can measure dimension and form simultaneously in scanning mode and also may employ surface roughness testers to perform measurements when the part is on the CMM machine. Use of probes for form measurements in scanning mode with a fast scanning speed might be problematic due to required high data acquisition rates, therefore the dynamic performance of the probe including the electronics of the instrument should be well calibrated. For the surface roughness devices, there is a need for new traceable standards due to a recent increase in the required measurement ranges (e.g. 1000 μm). Although there are documentation and methods for calibration of contact stylus instruments (ISO 12179; ISO 25178-701:2010 and DKD-R 4-2), there is no documentation for alternative routes or detailed investigations for calibration of reference stylus instruments used for calibration of reference standards of secondary level labs. The project, "Probe Trace"supported by the European Metrology Programme (EMPIR) has been started to respond to the above given demands. It aims to improve the scientific knowledge, instruments, methods and research capability in metrology for contact measurement probes and stylus instruments and enable calibration labs to develop new capabilities for selfprovision of traceability to the SI unit of length, the metre. Update on the project results will be given in the paper including, investigation of new traceability routes with displacement generators, software tools for use of spheres for calibration of the devices and noise reductions, and calibration of groove standards using various state of the art devices
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
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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