Rapid Consolidation of WC‑ZrSiO4 Hard Materials by Spark Plasma Sintering: Microstructure, Densification, and Mechanical Properties

Jeong‑Han Lee,Ik‑Hyun Oh,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

Densely consolidated WC-based hard materials with 5–20 vol% ZrSiO4was fabricated by spark plasma sintering at 1400 ℃ ata constant heating rate of 70 ℃/min−1. To achieve mechanical alloying of WC-ZrSiO4, planetary ball milling was carried outfor 12 h, during which the brittle-brittle components (WC-ZrSiO4) became fragmented and their particles became refined. Itwas observed that certain, specific, non-isothermal sintering kinetics, such as apparent activation energy, sintering exponents,and densification strain, affected the densification behavior. The evolution of phase structure from powder to compact wasfound to be related the lattice distortion and micro-strain in the basal planes of WC. By examining the mechanical propertiesof the samples, it was that the added zircon content leads to enhanced fracture toughness (12.9 MPa m1/2) owing to thepresence of WC-ZrSiO4 in the cemented carbide. In fact, the microcrack propagation of the fracture passed through zirconfrom a transgranular to a ductile component (fcc) where the crack tips could be absorbed.

초등학생에서 인두배양과 항-OF 항체 보유율

정현주,김선주,김윤정,맹국영,정현주,김선주,김윤정,맹국영 대한임상병리학회 1998 대한임상병리학회지 Vol.18 No.3

Influence of Phase Composition in TiAlSiN Hard Coatings on the Evolution of Structure and Mechanical Properties

Jeong‑Han Lee,Ik‑Hyun Oh,Jun‑Ho Jang,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.3

The aim of this study is to investigate the structural evolution and mechanical properties of TiAlSiN coatings when processedby the arc ion plating method. To form a hard coating, Ti, Al, and Si powders were mechanically alloyed by planetary ballmilling; the powders were then densely compacted during a rapid sintering process into a ternary system coating, i.e. TiAlSi. The evolution of the structural phase from a powder to a compact material is dominated considerably by phase states suchas a supersaturated solid solution or intermetallic compounds. In the case of coating layers, the factors that determine thestructural evolution are associated with the phase stability of the nano-crystalline structure that in turn is associated withthe Ti/Al composition ratio. Motivated by this, we performed experiments to investigate the distribution of microstructures;the material’s binding energy, quantitative properties, transformation of crystal structure, and distribution of amorphous/crystalline were all recorded. In particular, the relationship between the physical and chemical properties during the coatingprocess is considered to be the dominant factor controlling the orientation and morphology of that zone (1, T, and 2). TheTiAlSiN coating layer was found to have hardness above 45 GPa and an adhesion above 100 N. In other words, understandingthe evolution and structure of TiAlSin helped us to produce a material with excellent properties that can be used as a hardcoating. Specifically, these properties were induced by a grain refinement of the nano-crystalline structure that correspondsto an increase in the silicon nitride contents.

Effect of Mechanical Alloying on the Microstructural Evolution of Al60Cr30Si10 Alloys Processed by Spark Plasma Sintering

Jeong‑Han Lee,Ik‑Hyun Oh,Jun‑Ho Jang,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5

In this study, Al, Cr and Si fine powders were alloyed by planetary ball milling to investigate their microstructural evolution,following their mechanical alloying behavior. The formation of Al(Cr) supersaturated solid solution by the Cr grainsembedded in Al-matrix, which contributed substitutional structure is discussed in relation to their structural evolution inaccordance with the distortion of a crystal lattice. The compacts of Al–Cr–Si alloys were prepared by rapid sintering withina short time by dense consolidation above the density of 99.9% as the formation of intermetallics, except in the case of thedistribution of single-phases induced by the Al-melting. The formation behavior of intermetallics was dominated by dependenceon the structures of the milled-powder and subsequent sintering temperature. To estimate the consolidated behaviorsof compacts, various approaches derived from TEM and XRD analysis were taken to obtain microstructural evidences ofthe inter-diffusion, following the presence of thermally stable intermetallics.

방사선 치료를 받는 암 환자들의 사회적 지지와 삶의 질과의 관계

정주희,류소연,윤혜은,남택근,오윤경,안현옥,박계남,이영선 朝鮮大學校 附設 醫學硏究所 2002 The Medical Journal of Chosun University Vol.27 No.2

Objective : This study was performed to investigate the relationship between social support and quality of life among cancer patients receiving radiation therapy. Matehals and Methods : The data were collected from 98 patients, who were receiving radiation therapy at two university hospitals located in GwangUJu, used by structured questionnaire. For statistical analyses of the association between quality of life and various characteristics, data were analyzed using t-test, ANOVA, Pearson 's correlation, and multiple regression analysis. Results: 1. There were 56(57.1%) males and 42(42.9%) females. Age ranged from 21 to 82 years. The primary sites of cancer were gastrointestinal tract (24.5%), lung (23.5%), breast (21.4%), and head and neck (11.2%) in order. 2. The mean scores of social, family, and medical support were 4.30 0.58, 4.49 0.78, 4.11 0.65, respectively. The score of quality of life was 5.83 1.63 (range: 1.95 ~ 9.05). 3. An analysis of the association between several factors of patients and quality of life showed that the statistically significant factors were age, the presence of distant metastasis, family support, medical support and social support. 4. As a result of the multiple regression analysis, only social support was significant (β=0.932, P=0.02) with quality of life, but age and presence of distant metastasis were not significant. Conclusion : This suggests that quality of life in cancer patients could be improved by strengthening the social support which consists of family and medical support. Further study would be necessary to evaluate separately several aspects of quality of life among cancer patients.

백서 치주 골결손부에 calcium carbonate 이식 및 pulsed Nd : YAG 레이저에 의한 치은상피 제거후 접합상피 치유양상 YAG laser in rat peiodontal bone defect filled with calcium carbonate

정철웅,정현주 전남대학교 치과대학 1995 전남치대논문집 Vol.7 No.1

The purpose of this study was to evaluate whether removal of gingival epithelium with pulsed Nd : YAG laser could inhibit the downgrowth of junctional epithelium after alloplastic material grafting in periodontal bone defect. The periodontal bone defects were created surgically on the palatal aspect of the upper right and left molar teeth in 30 rats and filled with resorbable calcium carbonate(Biocoral 450?? : Inoteb, France). The control sites(right molar area) was sutured. The test side (left molar area) received controlled de-epithelization of the oral and sulcular epithelium with pulsed Nd : YAG laser(Sunrise Master?? : Sunrise Technologies, U.S.A.) under the mode of 1.75W, 15Hz, 116mJ/pulse and was sutured. The control and test sites were evaluated clinically and histologically, at 1, 3, 7, 14, and 28 days postoperation. Clinically, the gingiva showed normal color and shape at the 5th day in the control site and at the 10th day in the test sites. Histologically, the junctional epithelium was formed at the 7th day in the control sites and at the 14th day in the test sites, and the long JE attachment were observed at the 28th day in both sites. The attachment of connective tissue to root surface was observed initially at the 7th day in the control sites and at the 14th day in the test sites, and completed at the 28th day in both sites. In summary, these results showed that the removal of oral epithelium using pulsed Nd : YAG Laser could not prevent epithelial downgrowth after alloplastic material implantation in rat periodontal bone defect.

제어 시스템 설계를 위한 IEC 1131-3 기반의 제어 로직 생성기의 개발

정구,심주현,이제필,이철수 한국공작기계학회 2001 한국공작기계학회 춘계학술대회논문집 Vol.2001 No.-

This paper describes the methodology of an IEC 1131-3-based control logic generator for the control system design and converting algorithm between programmable languages. The proposed control logic generator is generated based on the software model and common element with data type, variables, POUs(program organization unit) and execution control unit commonly used within programmable languages of IEC 1131-3 Standard. The generation method of object file was proposed on five programmable language based on IEC1131-3. The generation method of object file is represented as following; 1) the generation method using conversion algorithm from LD to IL with FBD(function block diagram), 2) the generation method using C code generation algorithm from SFC using the SFC execution sequence with FBD and ST(structured text). The proposed control logic generator was implemented by Visual C++ and MFC on MS-windows NT 4.0

치주병원균에 대한 유산균의 억제효과

정하나,김영준,정현주,오종석 전남대학교 치과대학 1999 전남치대논문집 Vol.11 No.1

This study was performed to evaluate the effect of hydrogen peroxide-producing Lactobacillus acidophilus V-20 on the replication of periodontal pathogens, Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. When A. actinomycetemcomitans and P. gingivalis were incubated alone and in the combination with L. acidophilus V-20, the viable cell numbers of A. actinomycetemcomitans and P.gingivalis were compared between those cultures. The effect of S. mutans, E. durans, and L. lactis on the replication of A. actinomycetemcomitans and P. gingivalis was also evaluated. The change of periodontal indexes(probine depth, gingival index, GCF volume) and the viable cell numbers of A. actinomycetemcomitans and black pigmented bacteroides in subgingival plaque sample were evaluated following gargling of fermented milk made from L.acidophilus V-20 for 1 month on patients with periodontal disease in maintenance phase. In the mixed culture of L. acidophilus V-20 and A. actinomycetemcomitans or P. gingivalis, the replication of A. actinomycetemcomitans or P. gingivalis was completely inhibited. But in the mixed culture of P. gingivalis and hydrogen peroxide-nonproducing Lactobacillus casei, the viable cell numbers of P. gingivalis was not decreased when compared with the numbers in the mixed culture of P. gingivalis and L. acidophilus V-20. In the mixed culture of A. actinomycetemcomitans and S. mutans, E. durans, or L. lactis, the viable cell number of A. actinomycetemcomitans was not almost changed when compared with the numbers in the culture of A. actinomycetemcomitans alone. And in the mixed culture of P. gingivalis and E. durans or L. lactis, the viable cell numbers of P. gingivalis was not almost changed compared with the counts in the culture of P. gingivalis alone. But the replication of P. gingivalis was completely inhibited in the mixed culture of P. gingivalis and S. mutans. When the change of periodontal indexes following gargling of fermented milk was compared with baseline, probing depth and gingival index were not changed, but GCF volume was significantly decreased(p<0.05). And when the viable cell numbers of microorganisms in subgingival plaque sample were compared with baseline, total viable cell number was almost unchanged and the viable cell numbers of A. actinomycetemcomitans and black pigmented bacteroides were significantly decreased(p<0.05). These results suggest that L. acidophilus V-20 inhibit the replication of A. actinomycetemcomitans and black pigmented bacteroides by the formation of hydrogen peroxide.

Alendronate가 백서에서 두개골 결손의 재생에 미치는 영향

정찬두,김정근,정현주 전남대학교 치의학연구소 2001 구강과학 Vol.13 No.4

Previous studies have demonstrated an increase in bone mass and density with the use of bisphosphonate in osteoporosis. This agent acts as an inhibitor of osteoclastic activity, and results in increase of net osteoblastic activity. Currently, it has been reported that bisphosphonate has direct effect on osteoblast. This study was designed to evaluate the effect of alendronate on bone regeneration in defect of rat calvaria. The animals used for these experiments were 48 male rats, over 6-8 weeks old. They were divided into three groups according to the dose of alendronate(MK-217®, Merck, USA) administered. After the calvarial defects were surgically created, the rats received a peritoneal alendronate (0.25mg/kg) in group I, a peritoneal alendronate (1.25mg/kg) in group Ⅱ, and a peritoneal normal saline injection in the control group. Three and six weeks later, blood was sampled and evaluated for alkaline phosphatase activity. the animals were sacrificed for histological observation and histometric analysis of the level of bone formation. The alkaline phosphatase activity was similar in three groups at 3 weeks of experiment. The activity at 6 weeks increased more than twice, compared to 3 weeks, and was slightly higher in group Ⅰ than the other two groups. In histological observation, all the groups at 3 weeks, osteoblast rimming and new bone formation were observed along the defect margin. At 6 weeks, the defect was almost closed with new and more mature bone, but new bone is thinner than original bone in the central portion of defect. In histometric analysis, group Ⅰ and Ⅱ at 3 weeks showed significantly greater new bone formation than the control, and all the groups at 6 weeks showed similar amount of bone formation. These result suggest that alendronate administration in the dose of 0.25mg/kg and 1.25mg/kg promote osseous regeneration.

느타리버섯 신품종 육성 연구(I) : 병재배용 신품종『진미』느타리버섯의 특성

지정현,주영철,최종인 한국버섯학회 2004 한국버섯학회지 Vol.2 No.4

병재배 느타리버섯의 품종 다양화를 위해 단핵균주교잡에 의해 육성된 진미느타리버섯의 균사생장적온은 25∼30℃, 버섯발생 및 생육온도는 15±1℃이고 갓색은 회색이며 얕은깔대기형으로 발이수가 많았다. 배양일수는 20℃에서 22일, 초발이 소요일수는 4일이며 가늘고 긴형으로 농가실증시험에서 병당수량은 145.9g으로 높은 편이었다. 버섯의 갓색과 갓형태, 이형개체 발생,, 균사생장량, 종균배양기간 등에 대한 균일성도 양호하였고, 세균성 갈변병에 대한 저항성은 소정도로 나타났으나 푸른곰팡이병은 발생되지 않았다. 또한 균사 활력이 강하고 15 이하에서는 진한회색을 나타내며 육질이 부드럽고 대가 백색으로 깨끗한 직립형의 특성을 보유하고 있다. Jinmi oyster mushroom(Pleurotus ostreatus) were bred in Mushroom Research Institute, Gyonggi Province A.R.E.S in 2003. This oyster mushroom were bred and cultivated one after mating single spores collected from K3-2 and ASI2018-249. The major characteristics of the mushroom are showing a lot of pinheadings, the gray-colored and infundibuliform pileus. The optimum temperature for the mycelial growth was around 25∼30℃ and that for the pinheading and growth of fruitbody was around 15±1℃. Around 22 days at 20℃ were required for incubation of Jinmi and the yield was shown high by 145.9g/bottle.