• Korean Journal of Materials Research
• /
• v.19 no.2
• /
• pp.55-60
• /
• 2009

In this study, Ti powder was fabricated from Ti scrap by a hydrogenation-dehydrogenation (HDH) method. The Ti powders were compacted by Spark plasma sintering (SPS) and the microstructure and mechanical properties of the powders were investigated. A hydrogenation reaction of Ti scrap occurred at temperatures near $450^{\circ}C$ with a sudden increase in the reaction temperature and a decrease in the pressure of the hydrogen gas as measured in a furnace during the hydrogenation process. In addition, a dehydrogenation process was carried out at $750^{\circ}C$ for 2hrs in a vacuum of $10^{-4}torr$. The Ti powder sizes obtained by hydrogenation-dehydrogenation and mechanical milling processes were in the range of $1{\sim}90{\mu}m$ and $1{\sim}100{\mu}m$, respectively. To fabricate Ti compacts, Ti powders were sintered under an applied uniaxial punch pressure of 40 MPa at in a range of $900{\sim}1200^{\circ}C$ for 5 min. The relative density of a SPSed compact was 99.6% at $1100^{\circ}C$, and the tensile strength decreased with an increase in the sintering temperature. However, the hardness increased as the sintering temperature increased.

• Korean Journal of Materials Research
• /
• v.19 no.7
• /
• pp.397-402
• /
• 2009

In this study, Ti powder was fabricated from Ti scrap by the Hydrogenation-Dehydrogenation (HDH) method. Hydrogenation reactions of Ti scrap occurred at near 450 $^{\circ}C$ with a sudden increase in the reaction temperature and the decreasing pressure of hydrogen gas during the hydrogenation process in the furnace. The dehydrogenation process was also carried out at 750 $^{\circ}C$ for 2hrs in a vacuum of $10^{-4}$ torr. After the HDH process, a deoxidation treatment was carried out with the Ca(purity: 99.5) at 700 $^{\circ}C$ for 2hrs in the vacuum system. It was found that the oxidation content of Ti powder that was deoxidized with Ca showed noticeably lower values, compared to the content obtained by HDH process. In order to fabricate Ti compacts, Ti powder was sintered at $1100\sim1400^{\circ}C$ for 2hrs under a vacuum of $10^{-4}$ torr. The relative density of compact was 94.9% at 1300 $^{\circ}C$. After sintering, all of the Ti compacts showed brittle fracture behavior, which occurred in an elastic range with short plastic yielding up to a peak stress.

• Korean Journal of Materials Research
• /
• v.20 no.3
• /
• pp.125-131
• /
• 2010

In this study, Ti powders were fabricated from Ti scrap by the Hydrogenation-Dehydrogenation (HDH) method. The Ti powders were prepared from the spark plasma sintering (SPS) and their microstructure was investigated. Hydrogenation reactions of Ti scrap occurred at near $450^{\circ}C$ with a sudden increase in the reaction temperature and the decreasing pressure of hydrogen gas during the hydrogenation process in the furnace. The dehydrogenation process was also carried out at $750^{\circ}C$ for 2 hrs in a vacuum of $10^{-4}$ torr. After the HDH process, deoxidation treatment was carried out with the Ca (purity: 99.5%) at $700^{\circ}C$ for 2 hrs in the vacuum system. It was found that the oxidation content of Ti powder that was deoxidized with Ca showed noticeably lower values, compared to the content obtained by the HDH process. In order to fabricate the Ti compacts, Ti powder was sintered under an applied uniaxial punch pressure of 40 MPa in the range of $900-1200^{\circ}C$ for 5 min under a vacuum of $10^{-4}$ torr. The relative density of the compact was 99.5% at $1100^{\circ}C$ and the tensile strength decreased with increasing sintering temperature. After sintering, all of the Ti compacts showed brittle fracture behavior, which occurred in an elastic range with short plastic yielding up to a peak stress. Ti improved the corrosion resistance of the Ti compacts, and the Pd powders were mixed with the HDH Ti powders.

• Development and Reproduction
• /
• v.18 no.1
• /
• pp.43-49
• /
• 2014

Three species of Nortamea concinua (NC) and Haliotis discus hannai (HDH) from Tongyeong and Sulculus diversicolor supertexta (SDS) are widely distributed on the coast of the Yellow Sea, southern sea and Jeju Island in the Korean Peninsula under the innate ecosystem. There is a need to understand the genetic traits and composition of three mollusk species in order to evaluate exactly the patent genetic effect. PCR analysis was performed on DNA samples extracted from a total of 21 individuals using seven decamer oligonucleotides primers. Seven primers were shown to generate the unique shared loci to each species and shared loci by the three species which could be clearly scored. A hierarchical clustering tree was constructed using similarity matrices to generate a dendrogram, which was facilitated by the Systat version 10. 236 specific loci, with an average of 56.3 per primer, were identified in the NC species. 142 specific loci, with an average of 44.7 per primer, were identified in the HDH species. Especially, 126 numbers of shared loci by the three species, with an average of 18 per primer, were observed among the three species. Especially, the decamer primer BION-75 generated 7 unique loci to each species, which were identifying each species, in 700 bp NC species. Interestingly, the primer BION-50detected 42 shared loci by the three species, major and/or minor fragments of sizes 100 bp and 150 bp, respectively, which were identical in all samples. As regards average bandsharing value (BS) results, individuals from HDH species (0.772) exhibited higher bandsharing values than did individuals from NC species (0.655). In this study, the dendrogram obtained by the seven decamer primers indicates three genetic clusters: cluster 1 (CONCINNA 01~CONCINNA 07), cluster 2 (HANNAI 08~HANNAI 14), cluster 3 (SUPERTEXTA 15~SUPERTEXTA 21). Comparatively, individuals of HDH species were fairly closely related to that of SDS species, as shown in the hierarchical dendrogram of genetic distances.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.227-228
• /
• 2006

Powder injection molding (PIM) is a suitable technology for the fabrication of complex shape titanium and its alloys, and has a great potential in many applications. This paper dealt with the injection molding of hydride dehydrogenization (HDH) titanium powder, spheroidized HDH titanium powder and gas atomized titanium powder. Rheological and thermalgravimetric behaviors were compared between the feedstocks of the three powders, and a tentative application of Ti PIM to eye frame temple and bridge was briefed.

• The Korean Journal of Malacology
• /
• v.30 no.4
• /
• pp.383-390
• /
• 2014

The multiplex PCR system including six microsatellites from Haliotis discus hannai, consisting of dinucleotide and trinucleotide repeat units, is developed. The six loci were coamplified in a single reaction employing dye-labeled primers. Alleles from these loci were sized using an internal standard by automated sample processing in an ABI3100 Genetic Analyser. Amplified alleles in profiles containing selected microsatellites were typed clearly, providing easily interpretable results. In this results suggest that the presented multiplex PCR system may be a useful tool in a selective breeding program of H. discus hannai in which genetic identification will allow different genotypes to be reared together from fertilization. This should have a great impact as it will make selective breeding more efficient. Moreover, it will be useful in a variety of applications, including strain and hybrid identification, parentage assignment, pedigree reconstruction, estimating genetic diversity and/or inbreeding.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.12
• /
• pp.6159-6174
• /
• 2019

Recently, Kim et al. introduced the Hamming + k with m overlapped pixels data hiding (Hk_mDH) based on matrix encoding. The embedding rate (ER) of this method is 0.54, which is better than Hamming code HC (n, n - k) and HC (n, n - k) +1 DH (H1DH), but not enough. Hamming code data hiding (HDH) is using a covering function COV(1, n = 2^k -1, k) and H1DH has a better embedding efficiency, when compared with HDH. The demerit of this method is that they do not exploit their space of pixels enough to increase ER. In this paper, we increase ER using sequential Hk_mDH (SHk_mDH ) through fully exploiting every pixel in a cover image. In SHk_mDH, a collision maybe happens when the position of two pixels within overlapped two blocks is the same. To solve the collision problem, in this paper, we have devised that the number of modification does not exceed 2 bits even if a collision occurs by using OPAP and LSB. Theoretical estimations of the average mean square error (AMSE) for these schemes demonstrate the advantage of our SHk_mDH scheme. Experimental results show that the proposed method is superior to previous schemes.

• The Korean Journal of Malacology
• /
• v.25 no.3
• /
• pp.197-201
• /
• 2009

This study was conducted to investigate the genetic characteristics of wild population of Pacific abalone, Haliotis discus hannai in Dokdo island. We used six polymorphic microsatellite marker to investigate the genetic diversity and population structure. The loci Hdh1321 and Hdh512 had the highest number of allele (34 and 22 respectively) and loci Hdh145 and Awb083 had the lowest (5 and 7 respectively). The mean number of allele per locus was 14.8. The average observed and expected heterozygosities were 0.664 and 0.824 respectively, and the average $F_{IS}$ was 0.195. We compared the population genetic parameters of Dokdo population with previously published data of the same species. At the result, the parewise $F_{ST}$ test showed significant difference between the Dokdo population and six populations (published data), suggesting that the genetic relationship of Dokdo population was separated from six populations.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.11a
• /
• pp.38.1-38.1
• /
• 2009

산업이 발전함에 따라서 특수한 물성을 갖는 재료의 수요가 점점 증가하고 있는데최근 재료의 경량화, 화학적 안정화 등을 이용한 시스템의 효율성 향상, 환경오염방지 등과 같은 목적으로 사용재료의 고급화 추세가 현저해짐에 따라 티타늄 소재에 대한 관심과 수요가 증가하고 있다. 하지만, 국내에서는 티타늄 및 티타늄 합금의 원재료 및 가공제품을 대부분 수입에 의존하는 실정이다. 또한 티타늄 및 티타늄 합금의 스크랩의 경우 재활용률은 50~80%에 달하고 알려져 있으나 국내에는 이들의 재활용처리를 위한 시설이 없으며 폐기 또는 외국으로 저가로방출하고 있는 실정이다. 이에 따라 본 연구에서는 판재, 선재 및 관등의 기계 가공 시 주로 발생하는 티타늄 스크랩을 이용하여 HDH법을 이용하여 티타늄 분말을 제조하였다. 제조된 분말은 $900{\sim}1200^{\circ}C$의 온도범위에서 방전플라즈마소결공법을이용하여 소결체를 제작하였으며, 소결체의 강도, 경도 및미세조직 등을 평가하였다. 내식성향상을 위해 염화팔라듐을 이용하여 티타늄-팔라듐 분말 합금을 제조하여 티타늄 합금 분말의 소결체와 순수티타늄의 소결체와 내식성 비교를 위해 동전위분극시험을 통해 평가하였다.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.41 no.6
• /
• pp.466-470
• /
• 2008

Microsatellite DNA markers were used to investigate the genetic diversity and population structure of Pacific abalone Haliotis discus hannai collected from six locations (Uljin, Ulsan, Daechon, Taean, Wando, and Yosu) where hatchery-produced abalone have been released intensively. There was no distinguishable difference in the observed and expected heterozygosities between the six populations and a cultured population. However, there was a difference in the number of alleles per locus: 12.8 for the cultured population and 13.8 to 15.8 for the six populations. The proportion of stocked abalone ranged from 41.1 to 92.7% for wild-caught populations with a decreasing tendency of alleles per locus for an increasing proportion of stocked abalone. A departure from Hardy-Weinberg equilibrium (HWE) assessed using the Markov chain procedure (P<0.05) was observed in the six populations and cultured population at loci Hdh145 and Hdh5l2. The pairwise Fst test (P<0.05) showed a significant difference between the Uljin and Ulsan populations and four remaining populations (Wando, Daechon, Yosu, and the cultured population), among which the Wando population differed less than the other three populations (Daechon, Yosu, and the cultured population).