• Laser Solutions
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• v.11 no.2
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• pp.15-19
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• 2008

Electron beam (EB) weldability of pure grade Nb sheet was studied. One of Nb sheets was as-annealed and the other was cold rolled. Microstructures, Vickers hardness, and transverse weld tensile test were carried out for the base metal, the heat affected zone (HAZ) and weld metal. In the case of the EB welds made using the annealed Nb sheeet, fine equiaxed grains and coarse grains were dominant at the base metal and the HAZ, respectively, and columnar grains were observed at the weld metal. For the EB welds made using the cold rolled Nb sheet, elongated grains in the rolling direction at the base metal, and the microstructures of the weld metal and the HAZ are similar to those of the EB welds made using the annealed Nb sheet, respectively. For both annealed and cold rolled Nb sheet, the width of the HAZs are unusually wide in spite of using high density heat source, i.e. electron beam, and the grain sizes of both HAZs are similar. When tensile test was carried out using the transverse weld specimens, the failure occurred at the HAZ for both EB welds made using Nb sheets annealed and cold rolled, respectively and the tensile strengths of both specimens were 161MPa. Vickers hardness of EB welds made using annealed Nb was 56-57 Hv at both base metal and weld metal, 52-53 Hv at the HAZ. On the other hand, Vickers hardness of EB welds made using cold rolled Nb was 97-99 Hv at the base metal, but the hardness values of weld metal were similar to those obtained at the weld metal of annealed Nb.

• Korean Journal of Materials Research
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• v.28 no.12
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• pp.702-708
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• 2018

This study deals with the effect of microstructure factors on the strain aging properties of API X70 pipeline steels with different microstructure fractions and grain sizes. The grain size and microstructure fraction of the API pipeline steels are analyzed by optical and scanning electron microscopy and electron backscatter diffraction analysis. Tensile tests before and after 1 % pre-strain and thermal aging treatment are conducted to simulate pipe forming and coating processes. All the steels are composed mostly of polygonal ferrite, acicular ferrite, granular bainite, and bainitic ferrite. After 1 % pre-strain and thermal aging treatment, the tensile test results reveal that yield strength, tensile strength and yield ratio increase, while uniform elongation decreases with an increasing thermal aging temperature. The increment of yield and tensile strengths are affected by the fraction of bainitic ferrite with high dislocation density because the mobility of dislocations is inhibited by interaction between interstitial atoms and dislocations in bainitic ferrite. On the other hand, the variation of yield ratio and uniform elongation is the smallest in the steel with the largest grain size because of the decrease in the grain boundary area for dislocation pile-ups and the presence of many dislocations inside large grains after 1 % pre-strain.

• Archives of Plastic Surgery
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• v.48 no.1
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• pp.107-113
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• 2021

Background Applicants to integrated plastic and reconstructive surgery (PRS) residency in the United States spend exorbitant amounts of time and money throughout the interview process. Outside of first-hand experience through a visiting rotation, applicants utilize various resources in learning about a program. Today's applicants are "Millennials," the demographic cohort raised during the information age and proficient with digital technology. The authors evaluated whether programs have a presence on social media, and whether applicants are following these accounts. Methods An online survey was sent to applicants to a single integrated plastic surgery program evaluating basic demographics, social media utilization, and sources of information accessed throughout the residency application process. A manual search of popular social media platforms (Instagram, Facebook, and Twitter) was performed in October 2019. Accounts affiliated with integrated PRS programs were identified and analyzed. Results Eighty-four of 222 applicants (37.8%) completed the survey. Ninety-six percent of applicants were within the Millennial demographic. Ninety-six percent of applicants had some form of social media presence, with Facebook (90%) and Instagram (87%) being the most popular platforms. Seventy-three percent of applicants reported following a PRS residency social media account. As of October 2019, 59 integrated residency programs (73%) have active Instagram accounts. Conclusions Applicants still rely on the program website when researching potential residencies, but social media is being rapidly adopted by programs. Program social media accounts should be used as a dynamic form of communication to better inform applicants of program strengths and weaknesses.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.4
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• pp.185-192
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• 2022

Variations in the microstructure and mechanical properties of API X70 steel processed by piping, electrical resistance welding (ERW), and post seam annealing (PSA) are investigated in this study. In the welding zone, some elongated pearlites are formed and grains coarsening occurs due to extra heat caused by the ERW and PSA processes. After the piping, the base metal shows continuous yielding behavior and a decrease in yield and impact strengths because mobile dislocation and back stress are introduced during the piping process. On the other hand, the ERW and PSA processes additionally decreased the impact strength of welding zone at room and low temperatures because some elongated pearlites easily act as crack initiation site and coarse ferrite grains facilitate crack propagation. As a result, the fracture surface of the welding zone specimen tested at low temperature revealed mostly cleavage fracture unlike the base metal specimen.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.8
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• pp.1121-1129
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• 2022

Object recognition is carried out using RGB images in various object recognition studies. However, RGB images in dark illumination environments or environments where target objects are occluded other objects cause poor object recognition performance. On the other hand, IR images provide strong object recognition performance in these environments because it detects infrared waves rather than visible illumination. In this paper, we propose an RGB-IR fusion model, high-frequency interchange network (HINet), which improves object recognition performance by combining only the strengths of RGB-IR image pairs. HINet connected two object detection models using a mutual high-frequency transfer (MHT) to interchange advantages between RGB-IR images. MHT converts each pair of RGB-IR images into a discrete cosine transform (DCT) spectrum domain to extract high-frequency information. The extracted high-frequency information is transmitted to each other's networks and utilized to improve object recognition performance. Experimental results show the superiority of the proposed network and present performance improvement of the multispectral object recognition task.

• PNF and Movement
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• v.20 no.2
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• pp.147-156
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• 2022

Objective: Electrical stimulation is an assistive technology used to aid the recovery of upper limb use after stroke. The purpose of this systematic review was to determine the effects of electrical stimulation on upper extremity function in individuals with hemiparetic stroke and to develop an evidence base that supports the use of electrical stimulation for upper limb recovery after stroke. Design: A systematic review based on randomized controlled trials (RCTs). Methods: Studies published before April 20 2021 were collected for this review by searching PubMed, four other databases, and RCTs that reported the effects of electrical stimulation on upper extremity function in individuals with the characteristic stroke type. Information on the following parameters was extracted from each study: surname of first author, published year, country, participants, intervention, intervention's intensity, comparison, outcomes, additional therapy, and summary of results. This review also evaluated the bias within each study, including any selection bias, performance bias, detection bias, attrition bias, and reporting bias. Results: This review included five RCTs, and 208 stroke patients were included in the analysis. Stroke patients who underwent electrical stimulation showed significantly improved grip and pinch strengths, wrist range of motion, and basic daily living compared to those in the control group; however, there was no improvement in upper extremity function. Of the selected papers, 60% showed a "high risk" of performance bias, and 20% showed a "high risk" of detection bias. Conclusions: The results of this systematic review suggest that electrical stimulation provides some benefits to stroke patients, such as improved hand strength and range of motion. However, future studies are needed to provide clinical evidence of the effects of electrical stimulation on upper extremity function in stroke patients.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.1
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• pp.1-15
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• 2023

The aim of this study is to identify intelligent learning support functions in Learning Management System (LMS) to support university student learning activities during the transition from face-to-face classes to online learning. To accomplish this, we investigated the perceptions of students on the levels of importance and urgency toward learning support functions of LMS powered with Artificial Intelligent (AI) technology and analyzed the differences in perception according to student characteristics. As a result of this study, the function that students considered to be the most important and felt an urgent need to adopt was to give automated grading and feedback for their writing assignments. The functions with the next highest score in importance and urgency were related to receiving customized feedback and help on task performance processed as well as results in the learning progress. In addition, students view a function to receive customized feedback according to their own learning plan and progress and to receive suggestions for improvement by diagnosing their strengths and weaknesses to be both vitally important and urgently needed. On the other hand, the learning support function of LMS, which was ranked as low importance and urgency, was a function that analyzed the interaction between professors and students and between fellow students. It is expected that the results of this student needs analysis will be helpful in deriving the contents of learning support functions that should be developed as well as providing basic information for prioritizing when applying AI technology to implement learner-centered LMS in the future.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.34 no.2
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• pp.275-294
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• 2023

This study aims to analyze usability of public libraries' metaverse platform. This study also examines factors that affect usability and immersion of metaverse platform of Gangbuk culture information library, Hanbat library in Daejeon, and Mapo Central library. In order to conduct this study, 60 college students participated in online survey and experiment. There was a statistically significant positive relationship between learnability and usability, and between GUI and immersion in every library. Learnability and usability of Gangbuk culture information library were statistically significantly higher than other libraries. On the other hand, GUI score and immersion of Hanbat library was significantly higher than other libraries. However, given that there were few users connected to metaverse platform, there was no significant difference in interactivity among libraries. This study examines characteristics (including strengths and weaknesses) of metaverse platform of each library. It is expected that the results of this study could contribute to the improvement of usability of public library's metaverse platform.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.77.3-77.3
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• 2019

We present an analysis of the stellar population of compact elliptical galaxies (cEs) in various environments. Following conventional selection criteria of cEs, we created a list of cE candidates in the redshift range of z < 0.05 using SDSS DR12 catalog. We finally selected cEs with low-luminosity (Mg > 18.7 mag), small effective radius (Re < 600 pc), and high velocity dispersion (> 60 kms-1). We divide our cE sample into those inside and outside of the one virial radius of the bright (Mr < -21 mag) nearby host galaxy which is then defined as cEs with (cEw) and without (cEw/o) host galaxy, respectively. We investigated the stellar population properties of cEs based on the Hb, Mgb, Fe 5270, and Fe 5335 line strengths from the OSSY catalog. We found that cEw has a systematically higher metallicity than cEw/o. In the velocity dispersion-Mgb distribution, while cEw/o follows the relation of early-type galaxies, cEw are found to have a systematically higher metallicity than cEw/o at a given velocity dispersion. The different feature in the metallicity between cEw and cEw/o can suggest that two different scenarios can be provided in the formation of cEs. cEw would be the remnant cores of the massive progenitor galaxies that their outer parts have been tidally stripped by massive neighbor galaxies (i.e., nurture origin). On the other hand, cEw/o are likely to be faint-end of early-type galaxies maintaining in-situ evolution (i.e., nurture origin).

• Advances in nano research
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• v.15 no.6
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• pp.495-511
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• 2023

In this research, the impact of micro-silica, nano-silica, and polypropylene fibers on the fracture energy of self-compacting concrete was thoroughly examined. Enhancing the fracture energy is very important to increase the crack propagation resistance. The study focused on evaluating the self-compacting properties of the concrete through various tests, including J-ring, V-funnel, slump flow, and T50 tests. Additionally, the mechanical properties of the concrete, such as compressive and tensile strengths, modulus of elasticity, and fracture parameters were investigated on hardened specimens after 28 days. The results demonstrated that the incorporation of micro-silica and nano-silica not only decreased the rheological aspects of self-compacting concrete but also significantly enhanced its mechanical properties, particularly the compressive strength. On the other hand, the inclusion of polypropylene fibers had a positive impact on fracture parameters, tensile strength, and flexural strength of the specimens. Utilizing the response surface method, the relationship between micro-silica, nano-silica, and fibers was established. The optimal combination for achieving the highest compressive strength was found to be 5% micro-silica, 0.75% nano-silica, and 0.1% fibers. Furthermore, for obtaining the best mixture with superior tensile strength, flexural strength, modulus of elasticity, and fracture energy, the ideal proportion was determined as 5% micro-silica, 0.75% nano-silica, and 0.15% fibers. Compared to the control mixture, the aforementioned parameters showed significant improvements of 26.3%, 30.3%, 34.3%, and 34.3%, respectively. In order to accurately model the tensile cracking of concrete, the authors used softening curves derived from an inverse algorithm proposed by them. This method allowed for a precise and detailed analysis of the concrete under tensile stress. This study explores the effects of micro-silica, nano-silica, and polypropylene fibers on self-compacting concrete and shows their influences on the fracture energy and various mechanical properties of the concrete. The results offer valuable insights for optimizing the concrete mix to achieve desired strength and performance characteristics.