• 한국분말재료학회지
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• 제12권6호
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• pp.447-452
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• 2005

The synthesis and consolidation of titanium silicide by electro-discharge-sintering has been investigated. As-received Ti powder was in flaky shape and the mean particle size was $45.0{\mu}m$, whereas the mean particle size of the pre-milled Si powder with angular shape was $8.0{\mu}m$. Single pulse of 2.5 to 5.0 kJ/0.34g-elemental Ti and pre-milled Si powder mixture with the composition of $Ti-37.5at.\%$ Si was applied using $300{\mu}F$ capacitor. The solid with $Ti_5Si_3$ phase has been successfully fabricated by the discharge with the input energy more than 2.5kJ in less than $129{\mu}sec.$ Hv values were found to be higher than $1000kgf/mm^2$. The formation of $Ti_5Si_3$ occurred through a fast solid state diffusion reaction.

• Archives of Plastic Surgery
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• 제33권3호
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• pp.324-329
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• 2006

The silicone rubber implants are widely used in plastic surgery because of various advantages; however, calcification in surface of implant(as a chemical resistance) may transform or destroy the high molecular biomaterial when it stays too long within the human body. The purpose of this study is to determine the relationship between calcification and the histological disparities of the tissues surrounding the area adjoining the silicone nasal implant by examining the regional characteristics of calcium deposits in the silicone nasal implant via elemental analyses using EDX(energy-dispersive X-ray analysis) and ultrastructural analyses using SEM(scanning electron microscopy). The subjects of the study were 19 silicone nasal implants removed by revision rhinoplasty, all displaying calcification. According to the tissue characters, the implant surface was divided into 4 zones with the rhinion as the basis. For each zone, elemental and ultrastructural analyses were performed. Elemental analysis revealed that the calcium deposits consisted of Ca and P only. There were no statistically significant disparities among the ratios between Ca and P according to the zones. Ultrastructural analysis showed acellular mineral-like deposits coalesced to create amorphous deposits in all zones; however, in zones 1 and 3(more pressurized zones by periosteum or nasal bone), additional flaky cylinder-shaped calcium deposits were detected. Thus, it seems that the histological disparities in the surrounding tissues do not affect the components and their proportions in the calcification process. However, it can be inferred that the physical environment due to the histological disparities in the surrounding tissues affects the ultrastructures of calcium deposits.

• 분석과학
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• 제6권2호
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• pp.149-156
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• 1993

고온고압하(高溫高壓下)에서의 Ni-C 액상(液相) 중에서 구상흑연입자(球狀黑鉛粒子)의 형성과정을 밝히기 위한 실험적인 관찰을 행하였다. 구상 흑연입자는 다이아몬드 안정역에서 유지하는 동안 안정한 형태로 생성되어 성장하였다. 이 때의 구상 흑연입자는 다결정형태(多結晶形態)가 아닌 연속적으로 성장한 많은 결함을 포함하는 단결정형태(單結晶形態)(fullerene형(型))를 하고 있었다. 표면분석기(表面分析機)(Auger electron spectroscope) 및 고분해능(高分解能) 투과전자현미경(透過電子顯微鏡)을 이용한 분석결과 구상 흑연 입자는 $sp^2$ 및 $sp^3$ 결합을 갖는 탄소원자가 혼재(混在)되어 있는 결정상태임이 밝혀졌다. 다이아몬드 안정역으로부터 흑연 안정역으로 압력이 감소함에 따라 흑연입자의 모양이 구형(球形)에서 평판형(平板形)으로 연속적으로 변해가는 것이 관찰되었다. 다이아몬드 안정역에서 형성되는 구상 흑연입자는 $sp^3$ 결합을 가지는 탄소 원자의 안정적인 존재 때문인 것으로 해석되었다. 많은 결함을 포함하는 큰 크기의 fullerene형(型) 구상 흑연입자가 연속적으로 성장하는 사실은 Kroto가 예측한 대형 fullerene의 성장과정을 실험적으로 뒷받침해 주는 결과라 생각한다.

• 한국분말재료학회지
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• 제23권4호
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• pp.287-296
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• 2016

$Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders have been synthesized in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH using $NH_4OH$ as a chelating agent. The co-precipitation temperature is varied in the range of $30-80^{\circ}C$. Calcination of the prepared precursors with $Li_2CO_3$ for 8 h at $1000^{\circ}C$ in air results in Li $Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ powders. Two kinds of obtained powders have been characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analyzer, and tap density measurements. The co-precipitation temperature does not differentiate the XRD patterns of precursors as well as their final powders. Precursor powders are spherical and dense, consisting of numerous acicular or flaky primary particles. The precursors obtained at 70 and $80^{\circ}C$ possess bigger primary particles having more irregular shapes than those at lower temperatures. This is related to the lower tap density measured for the former. The final powders show a similar tendency in terms of primary particle shape and tap density. Electrochemical characterization shows that the initial charge/discharge capacities and cycle life of final powders from the precursors obtained at 70 and $80^{\circ}C$ are inferior to those at $50^{\circ}C$. It is concluded that the optimum co-precipitation temperature is around $50^{\circ}C$.

• 대한화장품학회지
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• 제25권1호
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• pp.37-54
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• 1999

분체 특성으로 매끄러운 사용감과 피부 부착력이 우수하며 판상의 체질안료보다 유동성이 큰 실리카 미립자를 제조하기 위해 실리카 조대입자의 제조와 이의 다단계 분쇄 공정을 이용하여 여러 층의 terrace를 가지고 있는 판상 체질안료의 표면과 다른 평골한 표면 상태의 평탄면을 가지는 실리카 미립자를 제조하였다 여기에서 제조된 실리카 단일 입자를 모입자로 사용함으로써 이산화티탄의 균일침전반응법에 의해 제조된 복합입자는 평탄면을 가지게 되어 유동성의 조절과 부착력의 조절에 의해 도포 층이 균일하게 형성되는 분체 특성을 가지고 있다 본 실험에서 가장 적합한 침전 반응의 조건은 요소농도가 0.2~0.3mol/$\ell$이고 황산농도가 0.3~O.4mol/$\ell$이고 황산티타닐의 농도가 0.007~0.015mol/$\ell$며, 반응온도는 60~8$0^{\circ}C$였다 이와 같은 균일 침전 반응의 조건에 따라 초미립자상 이산화티탄의 피복량과 피복된 초미립자의 입경을 제어함으로써 분체의 광학적 특성을 조절하였고, 그 결과 피부 도포 시 피부색에서 600nm이상의 장파장 영역에서 반사율을 증가시켜 강한 피부색 tone을 표현할 수 있도록 하였다.

• 한국재료학회지
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• 제27권12호
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• pp.664-671
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• 2017

A composite material was prepared for the bipolar plates of phosphoric acid fuel cells(PAFC) by hot pressing a flake type natural graphite powder as a filler material and a fluorine resin as a binder. Average particle sizes of the powders were 610.3, 401.6, 99.5, and $37.7{\mu}m$. The density of the composite increased from 2.25 to $2.72g/cm^3$ as the graphite size increased from 37.7 to $610.3{\mu}m$. The anisotropy ratio of the composite increased from 1.8 to 490.9 as the graphite size increased. The flexural strength of the composite decreased from 15.60 to 8.94MPa as the graphite size increased. The porosity and the resistivity of the composite showed the same tendencies, and decreased as the graphite size increased. The lowest resistivity and porosity of the composite were $1.99{\times}10^{-3}{\Omega}cm$ and 2.02 %, respectively, when the graphite size was $401.6{\mu}m$. The flexural strength of the composite was 10.3MPa when the graphite size was $401.6{\mu}m$. The lowest resistance to electron mobility was well correlated with the composite with lowest porosity. It was possible the flaky large graphite particles survive after the hot pressing process.

• Journal of Forest and Environmental Science
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• 제37권3호
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• pp.217-225
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• 2021

This study evaluated the species composition, diversity and phorophyte preference of epiphytes at the University of Port Harcourt located in southern part of Nigeria. Purposive sampling technique was used to select sites representing major avenues in the three campuses (Abuja, Choba and Delta) of the University. Data were collected on species name of phorophytes, number of individuals, diameter at breast height (dbh) and height, and species/number of epiphytes present on them. The points/sections of attachment of epiphytes on phorophytes were also recorded. A total of eight species of epiphyte belonging to six families were recorded in the study. Species diversity was higher in Abuja campus (Simpson 1-D=0.81; Shannon H=1.79), followed by Choba campus (Simpson 1-D=0.73; Shannon H=1.09) and Delta campus (Simpson 1-D=0.56; Shannon H=0.93). Species richness was highest in Abuja campus (n=8) followed by Delta campus (n=4) and Choba campus (n=3). Similarity in epiphyte species composition was highest between Choba and Delta campuses (85.71%), followed by Delta and Abuja campuses (66.67%) and lowest between Choba and Abuja campuses (54.55%). The family-Polypodiaceae, had the highest number of species (n=3). Microgramma owariensis had the highest relative abundance (27%) followed by Platycerium bifurcatum (26%) while Tillandsia utriculata and Peperomia pellucida had the least relative abundance (3%). Epiphyte abundance was weakly correlated with both the dbh and height of phorophytes. However, epiphytes were more abundant on phorophytes with rough/scaly/corky/flaky barks than on those with smooth barks. The planting of avenue tree species with rough barks is recommended to enhance the diversity of epiphytes in the study area.

• 대한본초학회지
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• 제32권3호
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• pp.89-95
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• 2017

Objectives : Seborrheic dermatitis is common abnormal skin condition characterized by flaking and itch. In seborrheic dermatitis, the flakes are greasy and yellowish. Inflammation is also observed. Through this paper we can understand the process of seborrheic dermatitis of the scalp and confirm the scalp changes in the treatment process. The purpose of this study was to report the clinical effects of herbal medicine on Seborrheic dermatitis Methods : We employed oriental medical treatments; herbal-medication (Hyeongbangpaedoksangamibang), infant acupuncture, moxibustion and blood therapy. We treated her three times a week. She took medicine three times a day after a meal. During taking medicine, we let her avoid fatty food, flour based food. Her father took a picture the patient's head parts and we compared the symptom with previous symptom. With the picture, we evaluated the patient's scalp condition. Results : After taking treatment, the scalp condition of the patient was much improved. At first, yellowish to reddish scaly pimples appear along the hairline and itching was severe. There were thick and black crusts on the scalp, red, greasy skin covered with flaky white or yellow scales. After that the crusts were fell off and the itching was disappeared during the treatment period. And then the hair loss was occurred. After a year of treatment, scalp condition and hair were back to normal. Conclusion : Herbal medicine (Hyeongbangpaedoksangamibang) with oriental medical treatments was effective in the treatment of seborrheic dermatitis of the scalp and it helped to improve regenerating the scalp condition.

• 지질공학
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• 제34권1호
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• pp.67-105
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• 2024

This study compares the quartzites of four quartzite units: The Fagfog Quartzite, Dunga Quartzite (member of the Robang Formation), Pandrang Quartzite (member of the Kalitar Formation) and the Chisapani Quartzite. The analysis shows variations in flakiness and elongation, as the Fagfog Quartzite displays low flakiness whereas the Pandrang and the Chisapani have moderate and the Dunga Quartzite has shown variations. The density values of the four quartzite units remain consistent, indicating uniform physical properties and porosity levels. However, bulk density values differ among the quartzites, suggesting variations in particle arrangement, porosity, and density. Regarding strength measures, the Pandrang and the Chisapani Quartzite have higher strength characteristics as compared to the Fagfog and the Dunga Quartzites. The Pandrang Quartzite has the highest average point load strength index, classifying it as "Extremely Strong". The resistance to impact and crushing forces varies among the quartzites, with lower Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV) indicating higher strength and durability. Durability tests show that the Fagfog Quartzite has high durability against slaking, with a slight decrease observed after the fifth cycle. The Dunga Quartzite shows varying degrees of weathering, while the Pandrang and the Chisapani Quartzite have minimal weight changes, indicating strong resistance to weathering. Magnesium sulfate soundness tests indicate high durability and resistance to degradation for all four units. The Los Angeles abrasion value (LAAV) tests indicate favorable resistance to abrasion for the majority of the Fagfog, Dunga, and the Pandrang Quartzites samples, while Chisapani Quartzite shows more variability in LAAV values. The Pandrang Quartzite shows a higher proportion of elongated particles but lower flakiness index values as compared to Fagfog and Dunga Quartzites while Chisapani Quartzite stands out with a significantly higher presence of flaky particles and lower elongation index values. Mechanically, the Fagfog and Dunga Quartzite show higher strength and better resistance to abrasion and freeze and thaw. The Pandrang Quartzite shows moderate resistance to crushing and sudden effect, while the Chisapani Quartzite has variable resistance to effect. This comparative study emphasizes the diversity and complexity of quartzite rock types, showing the need for comprehensive characterization and assessment to determine their suitability for specific applications.

• 한국광물학회지
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• 제5권2호
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• pp.102-108
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• 1992

장군광산의 산화망간광석에서 자연산 (Ca, Mg)-부서라이트를 발견하였는바, 이는 퇴적 또는 변성기원이 능망간석의 표성 풍화에 의해 형성되었다. 부서라이트는 란시아이트와 함께 세립의 부서라이트-란시아이트 염편을 이룬다. 이 (Ca, Mg)-부서라이트-란시아이트는 엽상의 작은 결정으로 산출되나. 이는 세립의 다카넬라이트 집합체 주위에 침전되어 있다. 전자현미분석 결과, 장군 광산의 (Ca, Mg)-부서라이트는 ($Ca_{.08}Mg_{.07}Mn_{.05}6{2+})Mn_{.89}^{4+}O_2{\cdot}1.46H_2O$의 화학식을 갖는다. 상대습도의 조절 및 가열에 의한 탈수실험과 상대습도 조절에 의한 재수화 실험에의하면, (Ca, Mg)-부서라이트는 90${\circ}C$에서 완전히 탈수되며 27%만이 재수화된다. 상대습도 26%에서의 (40$^{\circ}C$로 가열한 경우와 일치하는) 탈수현상은 9.86${\AA}$ 회절선의 9.60${\AA}$으로의 감소 및 강도의 감소로 특징지워진다. 이는 층간의 매우 약하게 결합된 물분자의 방출에 기인한다. 40$^{\circ}C$에서 90$^{\circ}C$까지의 가열에 의한 탈수현상은 001 회절선이 9.60${\AA}$에서 7.42${\AA}$까지 점이적 이동으로 특징지워진다. 이는 층간에 약하게 결합되어 있는 물분자의 방출에 의한 것이다.