Neutron studies on a highly frustrated 4d pyrochlore antiferromagnet Nd₂Ru₂O<SUB>7</SUB>

Sungkyun Choi 한국자기학회 2022 한국자기학회 학술연구발표회 논문개요집 Vol.32 No.2

Noncollinear magnetic order of a new magnetoelectric material determined by single-crystal neutron diffraction

Sungkyun Choi 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1

In magnetoelectric materials, the magnetic structure can be controlled using an electric field, or, conversely, the electric polarisation can be controlled using a magnetic field. Developing these materials could lead to the next generation of energy-efficient devices. One such candidate is Co4Ta2O9 that belongs to a new family of magnetoelectric materials, A4B2O9 (where A = Mn, Fe, Co and B = Nb, Ta). Its magnetoelectric behaviour, however, is uncommon and not understood until now. Here we used single-crystal neutron diffraction combined with direction-dependent magnetic susceptibility measurement to accurately determine the magnetic order [1]: key information to explain its novel magnetoelectricity [2]. We found that, below 20.3 K, Co4Ta2O9 exhibited unusual long-range antiferromagnetic order, where adjacent spins are pointing in opposite directions. The Co2+ ions form alternating the flat and buckled layers stacked along the vertical c-axis, with the magnetic moments lying in the horizontal plane. The buckled arrangement of magnetic ions can be a primary source of moments being aligned at a slight angle to one another, as shown in the figure below. Surprisingly, this magnetic structure is different to that observed for Co4Nb2O9, an isostructural and isoelectronic compound. Our result is unexpected, as it was thought that the magnetic behavior of both compounds was due to the Co2+ ions, suggesting that nonmagnetic Ta5+/Nb5+ ions may also influence their novel magnetic property. We further carried out symmetry analysis based on the determined magnetic order [1], which we were able to explain successfully why the peculiar magnetoelectricity is seen in Co4Ta2O9 [2]. (See figure in text)

Characteristics of archetypal Mott transitions in NiS2-xSex

Sungkyun Choi 한국자기학회 2023 한국자기학회 학술연구발표회 논문개요집 Vol.33 No.1

A Minimalist Approach to the Diachronic Study of English Modals

Sungkyun Shin 한국영어학학회 2006 영어학연구 Vol.- No.21

  This paper argues that the change from Old English to Modern English results from parameter-resetting as language acquisition (growth) results from parameter-setting. Through the diachronic study of English modals, the paper leads to the conclusion that Modern English modals are a result of parameter-resetting from the Old English premodals. This parameter-resetting is achieved through markedness, involving gradual changes of language. Language change, as suggested by Kroch (1989) and other scholars, shows an S-shaped curve in grammar change, not an abrupt change implied by parameter-resetting. This dilemma is solved by the introduction of a notion of markedness, mediated by phonologica,l, morphological, or syntactic change.

A Diachronic Study of the English Perfect Passive

Sungkyun Shin 한국영어학학회 2017 영어학연구 Vol.23 No.1

The English perfect passive was not used in Old English, in which the preterit passive was used instead of the present perfect passive. In early Middle English, the perfect passive came to be used and since then, its use has been increasing. Regarding the passive progressive, Visser (1963-73: §2158) prefers to see the main reason for the appearance of the passive progressive to be the “urge, permanently inherent in English as an analytic language, to signal separately every separate shade of meaning, function or connotation.” In other words, an analytic language such as English tries to express every aspect of verb phrases through periphrastic verb phrases, such as auxiliaries, which were expressed by full inflections in Proto-Indo-European. Likewise, if we observe a change in English verbal phrases, we find a direction of change concerning the English perfect passive. As English changed from Old English through Middle English and early Modern English to Present-day English, the pressure to fill the accidental gap -in this case, the perfect passive-was successfully resolved, resulting in the appearance of the perfect passive in the English language. Therefore, we assume two principles: one is the principle of filling the accidental gap: English changes to fill the accidental gap left by Proto-Indo-European as a result of the loss of inflections; and the other the principle of maximizing sequences of auxiliaries: concerning the verbal phrase, English changes to satisfy the maximal sequences of auxiliaries, which correspond to those of Proto-Indo-European. The two principles function together to do the same work.

Experimental Study on the Six Degree-of-Freedom Motions of a Damaged Ship Floating in Regular Waves

Sungkyun Lee,Ji-Myoung You,Hyun-Ho Lee,Taegu Lim,Sung Taek Park,Jeonghwa Seo,Shin Hyung Rhee,Key-Pyo Rhee IEEE 2016 IEEE JOURNAL OF OCEANIC ENGINEERING - Vol.41 No.1

<P>One of the most critical issues for ship owners, shipbuilders, and insurance companies is the operational safety. In particular, keeping damaged ships stable in waves is of great interest, because more nonconventional hull forms are being introduced for military and passenger vessels while international rules and regulations are becoming stricter. However, ship stability for damaged ships is quite different from that for intact ships as the assessment is very complicated and difficult due to the highly nonlinear behavior. Computational fluid dynamics (CFD) methods that solve the Navier-Stokes equations are acknowledged as the only viable approach to simulate and analyze these complex physical phenomena. Although there have been a number of research activities reported on damaged ship stability recently, most of them are not designed to validate CFD studies. For a data set to be valuable for CFD validation and development, model tests should eliminate unclear factors as much as possible. The main objective of this study is to establish an experimental database for CFD validation by collecting data from towing tank tests of a ship hull's six degree-of-freedom (6DOF) motion responses in regular waves for both intact and damaged conditions. A mooring system was designed to prevent drift motions of the ship model. Parametric roll was not observed when the ship was damaged, although it was observed for the intact ship in the same wave conditions. The mooring force acting on the ship model due to spring tension was also calculated.</P>

A Diachronic Study of the English Perfect Progressive Passive

Sungkyun Shin 한국중원언어학회 2018 언어학연구 Vol.0 No.47

Meaning of the English present perfect progressive refers to a state leading up to the present moment, focusing on the action itself. It is assumed that, in Proto-Indo-European, the perfect progressive passive of English such as the church has been being built is expressed by full inflection as in Greek and Latin. Analytic languages such as English first lost this perfect progressive passive with the loss of inflections; in the case of Germanic languages, this was a result of the falling of stress on the first syllable with the leveling of the unstressed vowels in English. English, being an analytic language, tries to fill this accidental gap, along with other gaps, through periphrastic verb phrases, including auxiliaries, rather than the use of Proto-Indo-European full inflections. The English language has been changing in the direction of maximizing the sequence of auxiliaries to satisfy the principle of filling the accidental gaps. This is evidence that the English language is a dynamic language, constantly undergoing changes.

Characterization of 3D laser-induced plasma temperature towards the development of flow diagnostics

Sungkyun Oh(오성균),Hyungrok Do(도형록) 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.5

THE AVAILABLE EVIDENCE REGARDING T’AEKKYŎN AND ITS PORTRAYAL AS A “TRADITIONAL KOREAN MARTIAL ART”

SUNGKYUN CHO,UDO MOENIG,DOHEE NAM 계명대학교 한국학연구원 2012 Acta Koreana Vol.15 No.2

Gitt’s Information Theory and Linguist Chomsky’s Fallacies

Sungkyun Shin 한국중원언어학회 2015 언어학연구 Vol.0 No.34

According to Gitt (1996; 2007), new information cannot originate through mutations, but mutations can only cause changes in existing information with no increase in information, and with injurious results. On the observation of this fact, Chomsky’s assumption that UG has happened to human beings through mutation(s) shows a fallacy. I rather support, with reference to Gitt’s information theory, Behe‘s (1996: 39) irreducible complexity, and Dembski’s (1999: 47) specified complexity based on intelligent design. Language is just a good example of irreducible complexity and specified complexity, showing the working together of speech anatomy, intelligence, and Chomsky’s internal system, which together consist of language use ( the internal system, intelligence, the sensory motor system, and externalization). Humans have a built-in brain capable of learning and conveying abstract ideas, faculty of language (Gitt’s information), and the physical anatomy (mouth, throat, flexible tongue, descended larynx, etc.) to produce a wide range of sounds. Language shows irreducible complexity and specified complexity based on intelligent design conforming to Gitt’s information theory.