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"Lee, Yoon Sun"
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Microstructure and Mechanical Properties of Hastelloy X Fabricated Using Directed Energy Deposition
Laser-aided additive manufacturing is used for complex shapes and Ni-based superalloy parts. This study aimed to optimize the additive manufacturing process of Hastelloy X alloy to obtain its excellent mechanical properties without pores or cracks in the additively manufactured parts. The additively manufactured Hastelloy X was analyzed by comparing porosity, microstructure, and mechanical properties in as-built and post-heat treatment conditions. In addition, the pores existing inside the as-built specimen considerably decreased after the hot isostatic press (HIP) treatment. Furthermore, cell/columnar microstructures were observed owing to a fast cooling rate in the as-built condition. However, after heat treatment, dendrite structures disappeared, and recrystallized equiaxed grains were observed. The tensile test results showed that there was mechanical anisotropy along the vertical and horizontal directions, and as the microstructure changed to equiaxed grains after heat treatment, the mechanical anisotropy decreased, and the high-temperature properties improved.
Journal Article
Diurnal Thermal Behavior of Photovoltaic Panel with Phase Change Materials under Different Weather Conditions
The electric power generation efficiency of photovoltaic (PV) panels depends on the solar irradiation flux and the operating temperature of the solar cell. To increase the power generation efficiency of a PV system, this study evaluated the feasibility of phase change materials (PCMs) to reduce the temperature rise of solar cells operating under the climate in Seoul, Korea. For this purpose, two PCMs with different phase change characteristics were prepared and the phase change temperatures and thermal conductivities were compared. The diurnal thermal behavior of PV panels with PCMs under the Seoul climate was evaluated using a 2-D transient thermal analysis program. This paper discusses the heat flow characteristics though the PV cell with PCMs and the effects of the PCM types and macro-packed PCM (MPPCM) methods on the operating temperatures under different weather conditions. Selection of the PCM type was more important than the MMPCM methods when PCMs were used to enhance the performance of PV panels and the mean operating temperature of PV cell and total heat flux from the surface could be reduced by increasing the heat transfer rate through the honeycomb grid steel container for PCMs. Considering the mean operating temperature reduction of 4 °C by PCM in this study, an efficiency improvement of approximately 2% can be estimated under the weather conditions of Seoul.
Journal Article
Structuralist Violence
Though narratives have been called on to expose the operation of structural violence, they threaten to reinforce neoliberal ideas of agency. This essay argues for a return to structuralism not in order to construct a universal grammar but to take narratives apart. Structuralism looks for virtual borders and connections, durable cuts and links. It reveals how apparently bounded forms are constituted and given power through the way they organize differences, adjuncts, substitutes, and contraries. Structuralism's interlocking abstractions can shed light now on kinds of violence that are not personal and not events.
Journal Article
Psychometric properties of the Korean Motor-free Visual Perception Test-4 in healthy people
Objective
This study was conducted to cross-culturally adapt the Motor-free Visual Perception Test 4 (MVPT-4) for use in Korean contexts and examine its psychometric properties.
Methods
The Korean MVPT-4 (K-MVPT-4) was developed via the process of translation, back-translation, and expert committee review. To establish internal consistency, test-retest reliability, concurrent validity and construct validity of the K-MVPT-4, 295 healthy people aged 10 to 79 years participated in this study. Participants completed the measures for the test-retest reliability on two occasions, 2 weeks apart.
Results
After three steps of cross-cultural adaptation, the K-MVPT-4 was revised to improve its alignment with Korean cultural norms. Cronbach’s α for internal consistency was .857 and intra-class correlation coefficient for test-retest reliability was .949. The K-MVPT-4 scores were significantly correlated with those of three motor-reduced subscales of the Korean Developmental Test of Visual Perception-Adolescent (K-DTVP-A) (r = .44–.46, p < .01). Participants’ age significantly influenced the K-MVPT-4 scores (p < .001) while their gender did not affect those scores (p = .409). As the age increased, the K-MVPT-4 scores decreased.
Conclusions
The findings indicated that the K-MVPT-4 is a reliable and valid test that Korean rehabilitation service providers can use with confidence to assess clients’ visual perceptual abilities.
Journal Article
Comparison of Dual-Permanent-Magnet-Excited Machines and Surface-Mounted Permanent Magnet Machines in Terms of Force
In this paper, finite element analysis demonstrates the difference between dual-permanent-magnet-excited machines (DPMM) and surface-mounted permanent magnet machines (SPM) in terms of tangential force at the same air gap, diameter, stacking length, and input current. Different from most conventional machines, a novel DPMM has two sets of permanent magnets employed on both stator and rotor. To make a fair comparison, the novel DPMM, based on an original design, is specified to have the same dimensions as a conventional SPM. With the aid of 2D finite element analysis, tangential force generated from the novel DPMM is 167.65% higher than the conventional SPM. To verify the validity of the analyses, a prototype was fabricated and tested. Experiments showed that average deviation was only approximately 1.85%.
Journal Article
p53/BNIP3-dependent mitophagy limits glycolytic shift in radioresistant cancer
The role of p53 in genotoxic therapy-induced metabolic shift in cancers is not yet known. In this study, we investigated the role of p53 in the glycolytic shift in head and neck squamous cell carcinoma cell lines following irradiation. Isogenic p53-null radioresistant cancer cells established through cumulative irradiation showed decreased oxygen consumption and increased glycolysis with compromised mitochondria, corresponding with their enhanced sensitivity to drugs that target glycolysis. In contrast, radioresistant cancer cells with wild-type p53 preserved their primary metabolic profile with intact mitophagic processes and maintained their mitochondrial integrity. Moreover, we identified a previously unappreciated link between p53 and mitophagy, which limited the glycolytic shift through the BNIP3-dependent clearance of abnormal mitochondria. Thus, drugs targeting glycolysis could be used as an alternative strategy for overcoming radioresistant cancers, and the p53 status could be used as a biomarker for selecting participants for clinical trials.
Journal Article
Vection, Vertigo, and the Historical Novel
Although accounts of the realist novel have not always adequately examined the experience of movement through space, this embodied epistemology is critical to the genre's development. Drawing on the physiology of perception as investigated by Erasmus Darwin and others, Scott makes the realist novel historical through the representation of motion as vertiginous sensation and as a problematic register of experience. The very uncertainty of the sensation of motion evokes history as a horizon rather than as a causal sequence. The term
came to be used later in the nineteenth century to refer to sensory uncertainty about whether movement in space is one's own or a sensation produced by external objects. For Scott, the related phenomena of vertigo and vection become perceptual metonyms of historical change. In the plot of vection, as opposed to the plot of action, movement cannot always be identified as forward or backward, up or down, as self-motion or as the ambient motion of the world. His novels engage the question of large-scale epochal historical transitions through the micro-level of the sensory experience of movement.
Journal Article
Correlation between Cellular Structure Morphology and Anisotropic Yield in Additively Manufactured Stainless Steel 316L
Additively manufactured austenitic stainless steel 316L is composed of a cellular structure, which has a directionality, and is observed with a different morphology depending on the observation direction. The cellular structure morphology that appears with a high probability in grains with a specific grain orientation is determined. Taylor factor, which is calculated by considering grain orientation, is related to cellular structure morphology due to the directional cellular structure in additively manufactured austenitic stainless steel 316L. The Taylor factor affects the mechanical properties. The yield strength of additively manufactured SUS316L can be explained by the correlation between cellular structure morphology, grain orientation, and Taylor factor.
Journal Article
Record of the Words and Deeds of Yuhandang Sa-ssi (Yuhandang Sa-ssi onbaengnok): An Annotated Translation by Michael C. E. Finch
KCI Citation Count: 0
Journal Article