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정희원,김승언,현용택,이용태,Jeong, Hui-Won,Kim, Seung-Eon,Hyeon, Yong-Taek,Lee, Yong-Tae 한국기계연구원 2001 硏究論文集 Vol.31 No.-
Silicon addition in titanium alloys generally results in solid solution hardening by silicon itself and precipitation hardening by titanium silicides. The morphology and distribution of the titanium silicides depend upon the alloy chemistry or the heat treatment condition, and play an important role in improving the mechanical properties of the alloys. In this study, the morphology and crystallographic characteristics of the titanium silicides in the Ti-Fe-Si alloy system were studied. Three types of silicides were found in the alloys; (1) interconnected chain-like silicides at grain boundary, (2) coarse silicides over im, (3) fine silicides smaller than 0.2m. Ti3Si was dominant in cast + HIP condition while Ti5Si3 was dominant in as-cast state. It is recognized that $Ti_5Si_3$$\rightarrow$$Ti_3Si$ transition occurred by the peritectoid reaction and it may be promoted by the pressure during HIP. However, in the case of the fine silicides, $Ti_3Si$ and $Ti_5Si_3$ were found simultaneously even after HIP. Such a fine silicide was found to have a crystallographic orientation relationship with matrix.
생체 친화적인 원소를 함유한 티타늄합금의 미세조직과 탄성계수
정희원,김승언,현용택,이용태,Jeong, Hui-Won,Kim, Seung-Eon,Hyeon, Yong-Taek,Lee, Yong-Tae 한국기계연구원 2003 硏究論文集 Vol.33 No.-
New titanium alloys with a low elastic modulus have been developed for biomedical applications to avoid the stress shielding effect of the artificial prosthesis. The newly developed alloys contained the transition elements like Zr, Hf, Nb, Ta which were non-cytotoxicity elements and $\beta$ stabilizers. In the present paper the elastic moduli of Ti-xM containing Zr, Hf, Nb, Ta were evaluated by measuring the acoustic velocity (PEG). The effectiveness of the alloying elements for lowering the elastic modulus was investigated. In addition, the dominant factors for the low modulus were discussed. Ta was the most effective in lowering the elastic modulus of the alloys. The effectiveness of Hf was not acceptable for decreasing the elastic modulus. The dominant factor was the lattice parameter for Zr, and the poisson's ratio for Nb, Ta, respectively.
Amortized Efficient zk-SNARK from Linear-Only RLWE Encodings
정희원,김동우,Kim, Jeong Han,Kim, Jiseung 한국통신학회 2023 Journal of communications and networks Vol.25 No.3
This paper addresses a new lattice-based designatedzk-SNARK having the smallest proof size in the amortized sense,from the linear-only ring learning with the error (RLWE) encod-ings. We first generalize a quadratic arithmetic programming(QAP) over a finite field to a ring-variant over a polynomialring Zp[X]/(XN + 1) with a power of two N. Then, wepropose a zk-SNARK over this ring with a linear-only encodingassumption on RLWE encodings. From the ring isomorphismZp[X]/(XN + 1) ∼= ZpN , the proposed scheme packs multiplemessages from Zp, resulting in much smaller amortized proofsize compared to previous works. In addition, we present a refined analysis on the noise floodingtechnique based on the Hellinger divergence instead of theconventional statistical distance, which reduces the size of a proof. In particular, our proof size is 276.5 KB and the amortizedproof size is only 156 bytes since our protocol allows to batchN proofs into a single proof. Therefore, we achieve the smallestamortized proof size in the category of lattice-based zk-SNARKsand comparable proof size in the (pre-quantum) zk-SNARKscategory.