Fabrication, Microstructures and High-Strain-Rate Properties of TiC-Reinforced Titanium Matrix Composites

Shin, Hyunho,Park, Hong-Lae,Chang, Soon-Nam 대한금속학회 2002 METALS AND MATERIALS International Vol.8 No.3

TiC ceramic particulate-reinforced titanium matrix composites were fabricated and the resultant densification, microstructure, and static and dynamic mechanical properties were studied. Comparing Ti with TiH_2 powders as host materials for TiC ceramic reinforcement by pressureless vacuum sintering, TiH_2-started composites showed better sinterability and resistance to both elastic and plastic deformation than Ti-started ones. When TiH_2 and TiH_2-45 vol.%TiC samples were hot pressed, TiH_2 matrices transformed to alpha prime Ti and alpha Ti phase, respectively. It is interpreted that the diffusion of an alpha stabilizer carbon from TiC into the matrix is one of the plausible reasons for such a microstructural difference. The 0.2% offset yield strengths of the hot pressed TiH_2 and TiH_2-45 vol.%TiC samples were 1008 and 1446 MPa, respectively, in a static compressive mode (strain rate of 1×10^-3/s). Dynamic compressive strengths of the samples were 1600 and 2060 MPa, respectively, at a strain rate of 4×l0^3/s.

A numerical investigation on determining the failure strength of a powder compact in unconfined compression testing by considering the compressible character of the specimen

Shin, Hyunho,Kim, Jong-Bong Elsevier 2015 Powder technology Vol.277 No.-

<P><B>Abstract</B></P> <P>The effect of the compressible character of a powder compact on the determined failure strength in unconfined compression testing is investigated numerically. The modified Drucker–Prager cap constitutive model (an elastic–plastic-work hardening model) is employed for a spray-dried Al<SUB>2</SUB>O<SUB>3</SUB> powder compact. When the failure strength is obtained from the current cross sectional area determined solely by the axial strain based on the assumption of incompressibility of the specimen, it underestimates the failure strength of the compressible specimen significantly. The degree of underestimation is magnified if the powder compact possesses a more slowly increasing hardening curve and/or a larger cap aspect ratio. Based on these findings, we suggest that the compressible character of the specimen be taken into account, especially for a powder compact with a slowly increasing hardening curve and/or with a large cap aspect ratio; the current cross sectional area of the specimen needs to be determined by measuring not only the axial strain but also the radial strain of the specimen.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Unconfined compression testing of a powder compact was simulated. </LI> <LI> The current area was determined for compressible and incompressible specimens. </LI> <LI> The failure strength was underestimated by the incompressibility assumption. </LI> <LI> The degree of underestimation increased when the hardening curve increased slowly. </LI> <LI> It was also magnified with the cap aspect ratio of the powder compact. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Titanium Carbide Nanocrystals Synthesized from a Metatitanic Acid-Sucrose Precursor via a Carbothermal Reduction

Shin, Hyunho,Eun, Jun-Ho Hindawi Limited 2015 Journal of nanomaterials Vol.2015 No.-

<P>A TiC powder is synthesized from a micron-sized mesoporous metatitanic acid-sucrose precursor (precursor M) by a carbothermal reduction process. Control specimens are also prepared using a nanosized TiO2-sucrose precursor (precursor T) with a higher cost. When synthesized at 1500°C for 2 h in flowing Ar, the characteristics of the synthesized TiC from precursor M are similar to those of the counterpart from precursor T in terms of the crystal size (58.5 versus 57.4 nm), oxygen content (0.22 wt% versus 0.25 wt%), and representative sizes of mesopores: approximately 2.5 and 19.7–25.0 nm in both specimens. The most salient differences of the two specimens are found in the TiC from precursor M demonstrating (i) a higher crystallinity based on the distinctive doublet peaks in the high-two-theta XRD regime and (ii) a lower specific surface area (79.4 versus 94.8 m<SUP>2</SUP>/g) with a smaller specific pore volume (0.1 versus 0.2 cm<SUP>3</SUP>/g) than the counterpart from precursor T.</P>

A refinement of the yield surface of a pressure-dependent and elastic-perfectly plastic constitutive model for a particulate compact by considering specimen barreling in triaxial testing

Shin, Hyunho,Kim, Jong-Bong Elsevier 2016 Powder technology Vol.301 No.-

<P><B>Abstract</B></P> <P>The effects of barreling of a particulate compact specimen caused by the end restraint and rubber membrane during a conventional triaxial test on the yield surface of a pressure-dependent and linearly elastic-perfectly plastic constitutive model are investigated via finite element analysis. The combined influence of the end restraint and rubber membrane results in barreling of the specimen which causes artifacts in the experimental deviator stress vs. strain curve determined in the triaxial test. Values of the shear-failure deviator strengths at varying confinement pressures have been modified to exclude the artifact caused by the specimen barreling, followed by the refinement of the yield-surface parameter set of the constitutive model. The refined set predicts the experimental curve better than the unrefined one does.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A linearly elastic-perfectly plastic constitutive model was employed. </LI> <LI> The model was used to simulate a conventional triaxial test. </LI> <LI> The specimen barrels due to the end restraint and rubber membrane. </LI> <LI> The yield surface parameters of the model were refined considering barreling. </LI> <LI> The refined yield surface parameters describe the experiment well. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Enhanced strain of InAs quantum dots by an InGaAs ternary layer in a GaAs matrix

Shin, Hyunho,Kim, Jong-Bong,Yoo, Yo-Han,Lee, Woong,Yoon, Euijoon,Yu, Young-Moon American Institute of Physics 2006 JOURNAL OF APPLIED PHYSICS - Vol.99 No.2

The Irish Fairies in W. B. Yeats's Early Poems

Shin, HyunHo(신현호) 한국외국어대학교 영미연구소 2015 영미연구 Vol.35 No.-

The purpose of this paper is to offer a viewpoint of the early poems of William Butler Yeats, focusing on the Irish fairies. W. B. Yeats was enthralled with Celtic mythology and the world of fairy. Much of Yeats’s early poetry and writing alludes to the Celtic otherworld, idealistic world and it adds a wonderful depth and richness to much of his work. Included are “The Stolen Child,” “A Faey Song,” “The Hosting of the Sidhe,” and “The Wanderings of Oisin.” Yeats tried to provide the individual ideals or visions for the Irish by incorporating the elements of Celtic mythology and Irish folklore in his poetry. Yeats’s early poems by fairies depict the conflict between the real and the ideal world. Yeats attempts to transcend the troubles of the real world by leaving for the ideal world that is represented by an eternal fairyland beyond time and space. But because of his ideal world, which is dreamy and eternally beautiful as it may be, and is so remote from the real world, he cannot attain the harmony between the real and ideal world. He does not blindly fly to the fantasy world in order to escape reality, but he wants a balance between the two.

A Comparative Study of Death in Donne’s and Yeats’s Poetry

Hyunho Shin 한국예이츠학회 2021 한국예이츠 저널 Vol.65 No.-

본 연구의 목적은 던과 예이츠의 시에 나타난 죽음에 대해 비교 고찰하 는 데 있다. 던이 죽음에 대해 가지는 태도는 죽음을 갈망하는 태도와 죽음을 끈질기 게 거부하는 양면적인 모습을 보인다. 이는 대립되는 것처럼 보이나 던은 둘 다 죽음 을 극복하고 통합하여 죽음이 인생의 끝이 아니라 죽음을 통해서만 죽음을 극복할 수 있다는 역설적 관점을 제시한다. 예이츠는 죽음을 삶의 영원한 끝이라고 보는 관점은 죽음에 대한 두려움에서 오는 감성적인 생각이라는 반응을 보인다. 예이츠는 죽음 이 후의 영혼의 존속과 육체의 환생에 대한 믿음을 보여준다. 던과 예이츠는 죽음이 삶의 끝이라는 것을 부인하나 죽음을 극복하는 방법은 상이하다. 던은 기독교 교리를 통한 신앙에 기초하여 죽음을 극복하나 예이츠는 예술의 영원성에 기초하고 있다. The purpose of the study is to offer a comparative interpretation of Donne’s and Yeats’s view of death in their poetry. Donne’s attitude toward death is characterized by two aspects: the positive attitude that desires death eagerly and the negative attitude that refuses death persistently. Though these two attitudes are paradoxical and in conflict, they are integrated into a transcendental attitude. Yeats expresses a disregard for life as any perpetual end in itself, a reaction against a sentimental and trite fear of death. Yeats has his beliefs in reincarnation and the survival of soul after death. Donne and Yeats refuse to think of death as the end of life. However, their approach to death is different. Donne’s way of surmounting death is faith in Christian doctrine, while Yeats asserts eternity and timelessness through art.

Crystal Phases, Photoluminescence, and Long-Afterglow Luminescence of SrAl2O4: Eu2+, Dy3+ - xB2O3 (0 x 0.4) Phosphors

Hyunho Shin,Shafqat Ullah,Byungwoo Park 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.1

SrAl2O4: 0.04Eu2+, 0.08Dy3+ - xB2O3 (0 x 0.4) phosphors were synthesized by using the conventional solid-state reaction route. The long-afterglow (LAG) luminescence increased notably up to x = 0.3, followed by a slight decrease at x = 0.4. A good correlation between the LAG luminescence and the total quantity of the luminescent crystalline phases (SrAl2O4 and Sr4Al14O25) was found, based on the Rietveld refinement of the X-ray diffraction pattern. However, through a comparison of the PL excitation/emission with the LAG luminescence, we concluded that the maximal LAG luminescence was not only governed by the quantity of the luminescent host but also by the quality of the host (the concentration of the doped Eu2+ and especially the Dy3+ in the luminescent phases).

A View of Afterlife in W. B. Yeats’s Later Poetry

Hyunho Shin 한국예이츠학회 2017 한국예이츠 저널 Vol.54 No.-

죽음과 그 이후의 삶에 대한 관심은 수세기동안 지속되어 왔다. 예이츠는 죽음 이후의 삶에 대해 『환상록』(A Vision)에서 밝힌 자신의 관점을 후기 시에 투영하고 있다. 이 연구의 목적은 예이츠 후기 시에 나타난 죽음 이후의 삶의 변모를 탐색하는 데 있다. 예이츠는 죽음 이후의 영혼의 과정을 4개의 원리(the Husk, the Passionate Body, the Spirit, and the Celestial Body)로 규정하고 6과정의 단계를 거쳐 변모한다고 주장한다. 자신의 창의적인 시를 통해 죽음 이후의 영혼의 환생과 생존에 대한 명상은 예이츠의 삶에 대한 강렬한 갈망이 잠복되어 있는 것으로 보인다. Death and afterlife of man have intrigued mankind for thousands of years. Yeats tries to answer these questions in his writings. Yeats successfully conveys his beliefs on the principles and details of afterlife in relation to the idea in A Vision and reflects them in his later poetry. The purpose of this study is to research the theme of afterlife in Yeats’s later poetry. Yeats elaborates the four principles of the soul — the Husk, the Passionate Body, the Spirit, and the Celestial Body. Yeats’s insatiable thirst for life, the desire, has expressed his belief in reincarnation and the survival of the soul after death in much of his later poetry.

Yeats’s Utopian Desire in “The Lake Isle of Innisfree” and “Byzantium”

Hyunho Shin 한국예이츠학회 2018 한국예이츠 저널 Vol.57 No.-

예이츠는 현실과 이상 사이에서의 갈등으로부터 자신의 이상향을 추구 하며 창출한 작가이다. 예이츠는 자신의 시를 통해 자신의 이상인 현실에서는 도달하기 어려운 유토피아를 모색한다. 본 논문은 「이니스프리」호도 에서 예이츠가 보여준 유토피아의 양상과 「비잔티움으로의 항해」를 쓴 동기, 그리고 「비잔티움」에 나타난 예 이츠가 상상한 완벽한 이상향을 살펴본다. 민족과 개인 그리고 상상력의 통합을 추구 했던 예이츠는 사람들에게 구원을 주는 이상향이 되는 유토피아를 상상한다. William Butler Yeats is one of the authors who created their own utopias out of their conflicts between the reality and the ideal. Certain metaphors of Yeats’s poems reveal his ideas of “Unity of Being,” utopia. This paper deals with the pattern of Yeats’s utopia in ‘The Lake Isle of Innisfree,’ and then Yeats’s motives to write ‘Sailing to Byzantium.’ Finally the hypothesis that Byzantium is the last destination of Yeats’s perfection is established in ‘Byzantium.’ Yeats seek to search for the unity of nations, races, and individual men and creative power of imagination. Yeats’s utopia can undertake for men to discover the ideal place which would offer them salvation.