• Kyungpook Mathematical Journal
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• v.62 no.4
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• pp.729-736
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• 2022

To help solving intractable nonlinear evolution equations (NLEEs) of waves in the field of fluid dynamics we develop an algorithm to find new high order solutions of the class of Abel, Bernoulli, Chini and Riccati equations of the form y' = ayⁿ + by + c, n > 1, with constant coefficients a, b, c. The role of this class of equations in NLEEs is explained in the introduction below. The basic algorithm to compute the coefficients of the power series solutions of the class, emerged long ago and is further developed in this paper. Practical application for hitherto unknown solutions is exemplified.

• Journal of the Korean Electrochemical Society
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• v.26 no.2
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• pp.19-34
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• 2023

Due to the intermittency of renewable energy sources, a need to store and transport energy will increase. Hydrogen production through water electrolysis will provide an excellent way to supplement the intermittency of renewable energy sources. While alkaline water electrolysis is currently the most mature technology, it has drawbacks of low current density, large footprint, gas crossover, etc. The PEM water electrolysis has potential to replace the alkaline electrolysis. However, expensive catalyst material used in the PEM electrolysis has been the bottleneck of widespread use. In this review, we have reviewed recent efforts to reduce catalyst loading in PEM water electrolysis. In core-shell nanostructures, the precious metal catalyst forms a shell while heteroatoms form a core. In this way, the catalyst loading can be significantly reduced while maintaining the catalytic activity. In another approach, a corrosion-resistant support is utilized, which provides a stable platform to impregnate precious metal catalyst.

• Steel and Composite Structures
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• v.47 no.1
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• pp.121-134
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• 2023

This paper tested 11 concrete-encased concrete-filled steel tube (CFST) composite columns and one reinforced concrete column under combined axial compression and lateral loads. The primary parameters, including the loading system, axial compression ratio, volume stirrup ratio, diameter-to-thickness ratio of the steel tube, and stirrup form, were varied. The influence of the parameters on the failure mode, strength, ductility, energy dissipation, strength degradation, and damage evolution of the composite columns were revealed. Moreover, a two-parameter nonlinear seismic damage model for composite columns was established, which can reflect the degree and development process of the seismic damage. In addition, the relationships among the inter-story drift ratio, damage index and seismic performance level of composite columns were established to provide a theoretical basis for seismic performance design and damage assessments.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.60.3-60.3
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• 2019

Binary systems of a white dwarf showing mass transfer activities are classified into cataclysmic variables and symbiotic stars. In the case of cataclysmic variables, the companion is usually a late type main sequence star filling its Roche lobe, where material is transferred through the inner Lagrangian point to form an accretion disk around the white dwarf. The disk becomes unstable and highly viscous when the surface density exceeds the critical density, leading to dwarf nova outbursts. In contrast, symbiotic stars are wide binary systems having a giant as the mass donor. Some fraction of giant stellar wind is accreted to the white dwarf giving rise to various symbiotic activities. In particular, half of symbiotics show Raman O VI at 6830 and 7088, which are important spectroscopic probe of mass transfer process. Monitoring observations using 1 m class telescopes will produce valuable information regarding the mass loss and mass transfer to white dwarf stars, shedding much light on the last stage of stellar evolution of low and intermediate mass stars.

• Animal Systematics, Evolution and Diversity
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• v.39 no.3
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• pp.127-132
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• 2023

Aquilonastra doranae, a newly recorded sea star, was collected from the southern coast of Jejudo Island by a trimix SCUBA diving survey in May 2021. The newly collected specimen is distinguished from a previously known Aquilonastra species in South Korea by having a fissiparous body form with six arms. Results of pairwise genetic distance analysis showed that the new specimen was identical or close to A. anomala from Hawaii (0.0%), Australia (3.1%), and Samoa (3.3%). However, morphological characteristics of the Korean Aquilonastra specimen corresponded with the original description of A. doranae, not that of A. anomala, including the number of inferomarginal spines, the absence of pedicellariae, and the inhabit locality. Thus, this study agrees with the original morphological study of A. doranae and presents this specimen as the first record of A. doranae in South Korea.

• Animal Systematics, Evolution and Diversity
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• v.39 no.4
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• pp.314-318
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• 2023

The genus Athanas is a member of alpheid shrimps living in temperate and tropical waters worldwide. Species of the genus Athanas are small and inhabit coral reefs, rock or muddy bottoms. As a result of continuous taxonomic research on shrimps collected from Korean waters, Athanas parvus is newly added to Korean fauna through the description of adult form. Athanas parvus is distinguished from A. japonicus by the biunguiculated dactyli of third, fourth and fifth pereopods and spines on ischium of first pereopod. The Korean Alpheidae fauna now consists of nine genera and 27 species including two species of the genus Athanas.

• Animal Systematics, Evolution and Diversity
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• v.40 no.1
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• pp.42-46
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• 2024

Two species from the genus Escharoides Milne Edwards, 1836, E. biseriatata and E. buffonellarioides n. sp. Were first found in Korean waters in this study. Their colonies were collected from two locations in the South Sea, Korea: Tongyeong Marine Ranch in 2004 and Daebyeon Port in 2009. Escharoides biseriatata shows a difference in the position of avicularia from the Chinese specimens. While avicularia are lateral to the orifice in Chinese specimens, the ones in Korean specimens seem to be located more latero-proximally. Since Escharoides biseriatata was reported as fouling bryozoans in China in 2001, this species first occurred at Daebyeon Port in Korea in this study. Escharoides buffonellarioides n. sp. is similar to E. adeonelloides in morphological features of zooids but is clearly distinguished by having the erect colonial form of small masses. With the addition of two species reported herein, four Korean Escharoides are recorded: E. biseriatata, E. buffonellarioides, E. excavata, and E. sauroglossa.

• Animal Systematics, Evolution and Diversity
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• v.40 no.1
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• pp.102-107
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• 2024

Two colonial ascidians, Eudistoma glaucum and Eudistoma purpureum, are reported for the first time in Korean waters through taxonomic study on ascidians collected from a subtidal zone of Jejudo Island. Eudistoma glaucum is distinguished by opaque green color of colony in living, massive colony with large corona, smooth surface of corona, sparse sand only at the peduncle, zooids in circle, about 8-10 stigmata of 3 stigmata rows and test process. Eudistoma purpureum is distinguished by brilliant, opaque, purple color of colony in living, less lobed colony form, smooth shiny surface, sparse sand only at the basal test, absence of symbionts, zooids in circle, no distinct bulging sphincter in siphon, long atrial siphon and about 20 stigmata of 3 stigmata rows. As a result of this study, four species of the genus Eudistoma are now recorded in Korean fauna.

• Archives of Metallurgy and Materials
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• v.65 no.3
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• pp.1069-1072
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• 2020

Mortar feedstock is extruded to form bead and it is selectively placed line by line in the material extrusion additive manufacturing. With respects to part building process healthiness, load-supporting ability of overlaid beads is emphasized as buildability. Buildability is primarily dependent on thixotropic properties of feedstock and vertical overlapping schedule. In the present study, water-to-binder (w/b) ratio was chosen as material aspect to assess buildability. Uneven bead shape evolution and premature failure were highlighted owing to low yield stress of high w/b ratio feedstock. Feedstock with optimum w/b ratio showed good buildability even at the interval time of 19 sec.

• Animal Systematics, Evolution and Diversity
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• v.15 no.2
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• pp.165-174
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• 1999

Specimens of five species of Apodemus(A. agrarius, A. chevrieri, A. draco, A. latronum, and A. peninsulae) from east Asia (Korea and China) were used for numerical taxonomic analyses with 31 external and cranial characters. Two groups and eight subgroups within them were recognized: [I; a large-size form; (A. agrarius chejuensis), (A. chevrieri), (A. draco orestes and A. latronum), and(A. peninsulae peninsulae and A. p. preator)], [II; a small-size form; (A. agrarius coreae), (A. agrarius manchuricus, A. a. ningpoensis, and A. a. pallidior), (A. draco draco), and (A. peninsulae sowerbyi)]. Conclusions based on morphometric analyses are such as followings: 1) Morphometric characters appeared not to be useful in order to distinguish two subgenera in Apodemus (Apodemus and Alsomys), 2) further analysis is necessary to determine whether or not A. draco and A. latronum are conspecific, and 3) A. a. chejuensis is in morphometric characters the largest form among five species of Apodemus studied. Moreover, it is confirmed: 1) A. agrarius, A. chevrieri, and A. peninsulae are distinct species, 2) A. draco and A. latronum are not conspecific with A. peninsulae. 3) Three forms of A. agrarius (large-size form, medium-size form, and small-size form) can be recognized as three subspecies [(A. a. chejuensis), (A. agrarius coreae), and (A, a, ningpoensis including A. a. manchuricus and A. a. pallidior)], 4)A. draco draco and A. draco orestes are distinct subspecies, 5) A. peninsulae peninsulae (including A. p. preator) and A. p. sowerbyi are distinct subspecies.