1,720,990 research outputs found
FORMATION OF SECONDARY VORTEX DURING VORTEX-WEDGE INTERACTION
No full textThis work was supported in part by Korea Science and Engineering
Foundation 891-0916-01 1-2
DISCRETE VORTEX SIMULATION OF PULSATING FLOW BEHIND A NORMAL PLATE
No full textA numerical study is made of the separated flow behind a flat plate. The plate is placed normal to the direction of the approach flow. The oncoming freestream velocity contains a pulsating part, U infinity = U-0(1+A(0)cosf(p)t). The temporal behavior of vortex shedding patterns is scrutinized over broad ranges of the two externally specified parameters, i.e., the pulsation amplitude (A(0) less than or equal to 0.6), and the dimensionless pulsation frequency, (f(b) less than or equal to 0.32). A version of the discrete vortex method is utilized. The variable-position nascent vortex technique is applied, and it proves to be adequate for pulsating approach flows. The numerical results clearly capture the existence of lock-on when f(p) exceeds a threshold value. The modulation of vorticity shedding is also detected when f(p) is reasonably low. The influence of A(0) on the flow characteristics is examined in detail. As A(0) increases to a moderate value (e.g., A(0) less than or equal to 0.6), an appreciable broadening is seen of the range of f(p) for which lock-an occurs. Based on the numerical results, three characteristic flow modes in the wakes are identified. These findings are qualitatively consistent with the existing flow visualization studies for a cylinder
Atypical pulmonary cysts in lung cancer screening: prevalence, outcomes, and clinical implications
No full textOBJECTIVE: We aimed to examine the prevalence and clinical outcomes of atypical pulmonary cysts (APCs) in lung cancer screening (LCS) and evaluate the impact of APC introduction on Lung-RADS v2022 categorization. MATERIALS AND METHODS: We reviewed 2968 low-dose baseline chest CT scans from LCS participants between June 2017 and April 2023. Two thoracic radiologists assessed the presence and type of APCs and evaluated interval changes. We also investigated how the introduction of APC changed Lung-RADS categories. Interobserver agreement was assessed using Cohen's kappa coefficient. RESULTS: Of the 2968 participants (2900 men, 68 women; median age: 61 years [IQR: 57-65]), 18 (0.6%) had APCs. The interobserver agreement for APC presence was fair (kappa = 0.33; 95% CI: 0.07-0.44). Among the 16 APC cases with follow-up CTs (median follow-up: 22 months), lung cancer was confirmed in three cases (18.8%). Among the remaining 13 APCs, 4 (30.8%) showed growth, 7 (53.8%) showed no change and 2 (15.4%) exhibited decreased wall thickness. Histological confirmation was not obtained for these 13 cases, indicating a minimum cancer rate of 18.8%. The introduction of APC led to a positive result change in 0.4% of participants (12/2968), with two lung cancer cases among them. CONCLUSION: APCs were infrequent in LCS, with a 0.6% prevalence, but had a high cancer rate (18.8%). Although the introduction of APC led to a 0.4% increase in positive screenings, this is considered acceptable as it included two lung cancer cases, highlighting the importance of recognizing APCs for early lung cancer detection. KEY POINTS: Question What is the prevalence and clinical significance of APCs detected during LCS, and how do they impact diagnostic outcomes? Findings APCs were detected in 0.6% of participants, with a high cancer rate of at least 18.8%, and increased screening positive results by 0.4%. Clinical relevance APCs during LCS, although uncommon, are crucial because of their high risk of lung cancer. This enhances early detection of lung cancer and improves patient management strategies
Interreader Agreement of Lung-RADS: A Systematic Review and Meta-Analysis
No full textBACKGROUND. Lung-RADS has shown variable interreader agreement in the literature, in part related to a broad range of factors that may influence the consistency of its implementation. OBJECTIVE. The purpose of this study was to assess the interreader agreement of Lung-RADS and to investigate factors influencing the system's variability. EVIDENCE ACQUISITION. The Embase, PubMed, and Cochrane databases were searched for original research studies published through June 18, 2024, that reported the interreader agreement of Lung-RADS on chest CT. Random-effects models were used to calculate pooled kappa coefficients for Lung-RADS categorization and pooled intraclass correlation coefficients (ICCs) for nodule size measurements. Potential sources of heterogeneity were explored using metaregression analyses. EVIDENCE SYNTHESIS. The analysis included 11 studies (1470 patients) for Lung-RADS categorization and five studies (617 patients) for nodule size measurement. Interreader agreement for Lung-RADS categorization was substantial (kappa = 0.72 [95% CI, 0.57-0.82]), and that for nodule size measurement was almost perfect (ICC = 0.97 [95% CI, 0.90-0.99]). Interreader agreement for Lung-RADS categorization was significantly associated with the method of nodule measurement (p = .005), with pooled kappa coefficients of 0.95, 0.91, and 0.66 for studies using computer-aided detection (CAD)-based semiautomated volume measurements, CAD-based semiautomated diameter measurements, and manual diameter measurements, respectively. Interreader agreement for Lung-RADS categorization was also significantly associated with studies' nodule type distribution (p < .001), with pooled kappa coefficients of 0.85, 0.76, and 0.55 for studies evaluating 100% solid nodules, 30-99% solid nodules, and fewer than 30% solid nodules, respectively. Interreader agreement for nodule size measurement was significantly associated with radiation dose (p < .001), with pooled ICCs of 0.97, 0.96, and 0.59 for studies that used standard-dose CT, low-dose CT, and ultralow-dose CT, respectively. Interreader agreement for nodule size measurement was also significantly associated with the Lung-RADS version that was used (p = .02), with pooled ICCs of 0.99 and 0.93 for studies using Lung-RADS 1.1 and Lung-RADS 1.0, respectively. CONCLUSION. Although they support the overall reliability of Lung-RADS, the findings indicate roles for CAD assistance as well as training and standardized approaches for nodule type characterization to further promote reproducible application. CLINICAL IMPACT. Consistent nodule assessments will be critical for Lung-RADS to optimally impact patient management and outcomes
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
Effect of heat treatment and mandrel material on precision tube drawing of Ni-Ti shape memory alloy
No full textThe Ni-Ti shape memory alloy (NITINOL) was known as one of difficult materials to meet the dimensional accuracy because of the complex phase transformation and the shape recovery characteristics. In this study, a tube drawing process with mandrel was numerically and experimentally investigated for manufacturing precision NITINOL tube to identify the stable phase transformation condition to remove the R-phase by differential scanning calorimeter. To study the non-linear material and shape recovery behavior of the NITINOL, tension and loading-unloading tests were conducted with three test velocities of 1, 5, and 10 mm/min. The three dimensional finite element (FE) analyses were carried out using the ABAQUS with hyperelastic and Mullins effect model. The amount of the shape recovery was checked for the drawn tubes compared to the numerical results. According to the present investigation, it was found out that the stable phase transformation which improved the ductility and reduced the effect of shape recovery was occurred under the condition of the heat treatment at 700 degrees C for 30 min and the tensile test velocity of 10 mm/min. The FE results showed similar tendency of the stress-strain curves obtained from the experiments. Moreover, the amount of the shape recovery of the NITINOL could be predicted by the FE analysis. From the results of the FE analysis and the tube drawing with red copper and brass mandrel, the dimensional accuracy was found to be improved by using the brass mandrel, but the drawing stress was somewhat higher for the brass mandrel than the case using the red copper mandrel. In conclusion, the shape recovery effect of the NITINOL could be predicted by the FE analysis and the process condition determined by the current experiments could be helpful for the precision tube drawing of the NITINOL shape memory alloy tube
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
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