液狀燒結한 SiC系의 傳導性 複合體의 微細構造와 特性에 미치는 Boride의 影響

辛龍德(Yong-Deok Shin),朱陳榮(Jin-Young Ju),高台憲(Tae-Hun Ko) 대한전기학회 2007 전기학회논문지 Vol.56 No.9

The composites were fabricated. respectively, using 61[vol.%] SiC-39[vol.%] TiB₂ and using 61[vol.%] SiC-39[vol.%] ZrB₂ powders with the liquid forming additives of 12[wt%] Al₂O₃+ Y₂O₃ by hot pressing annealing at 1650 [℃] for 4 hours. Reactions between SiC and transition metal TiB₂. ZrB₂ were not observed in this microstructure. The result of phase analysis of composites by XRD revealed SiC(6H. 3C), TiB₂; ZrB₂ and YAG(Al?Y₃O₁₂) crystal phase on the Liquid-Phase-Sintered(LPS) SiC-TiB₂. and SiC-ZrB₂ composite. β→a-SiC phase transformation was occurred on the SiC-TiB₂ and SiC-ZrB₂ composite. The relative density, the flexural strength and Young's modulus showed the highest value of 98.57[%], 249.42[㎫] and 91.64[㎬] in SiC-ZrB₂ composite at room temperature respectively. The electrical resistivity showed the lowest value of 7.96×10?⁴[Ωㆍ㎝] for SiC-ZrB₂ composite at 25[℃], The electrical resistivity of the SiC-TiB₂ and SiC-ZrB₂ composite was all positive temperature coefficient resistance (PTCR) in the temperature ranges from 25[℃] to 700[℃]. The resistance temperature coefficient of composite showed the lowest value of 1.319×10?³/[℃] for SiC-ZrB₂ composite in the temperature ranges from l00[℃] to 300[℃]. Compositional design and optimization of processing parameters are key factors for controlling and improving the properties of SiC-based electroconductive ceramic composites.

자기 통전식 SiC 세라믹 발열체 개발을 위한 기초 특성 연구

신용덕(Yong-Deok Shin),고태헌(Tae-Hun Ko),주진영(Jin-Young Ju) 대한전기학회 2007 대한전기학회 학술대회 논문집 Vol.2007 No.11

The composites were fabricated β-SiC and TiB₂ powders with the liquid forming additives of 8, 12, 16[wt%] Al₂O₃+Y₂O₃ as a sintering aid by pressureless annealing at 1,650[℃] for 4 hours. Reactions between SiC and transition metal TiB₂ were not observed in the microstructure and the phase analysis of the pressureless annealed SiC-TiB₂ electroconductive ceramic composites. The relative density, the flexural strength, the Young's modulus and the Vicker's hardness showed the highest value of 82.29[%], 189.5[㎫], 54.60[㎬] and 2.84[㎬] for SiC-TiB₂ composites added with 16[wt%] Al₂O₃+Y₂O₃ additives at room temperature. The relative density of SiC-TiB₂ composites was lowered due to gaseous products of the result of reaction between SiC and Al₂O₃+Y₂O₃. The electrical resistivity showed the lowest value of 0.012[Ω · ㎝] for 16[wt%] at 25[℃]. The electrical resistivity was all negative temperature coefficient resistance (NTCR) in the temperature ranges from 25[℃] to 700[℃].

常壓燒結한 SiC-ZrB₂ 電導性 複合體의 特性에 미치는 In Situ YAG의 影響

辛龍德(Yong-Deok Shin),朱陣榮(Jin-Young Ju),高台憲(Tae-Hun Ko),李政勳(Jung-Hoon Lee) 대한전기학회 2008 전기학회논문지 Vol.57 No.11

The effect of content of Al₂O₃+Y₂O₃ sintering additives on the densification behavior, mechanical and electrical properties of the pressureless-sintered SiC-ZrB₂ electroconductive ceramic composites was investigated. The SiC-ZrB₂ electroconductive ceramic composites were pressurless-sintered for 2 hours at 1,700[℃] temperatures with an addition of Al₂O₃+Y₂O₃(6 : 4 mixture of Al₂O₃ and Y₂O₃) as a sintering aid in the range of 8 ~ 20[wt%]. Phase analysis of SiC-ZrB₂ composites by XRD revealed mostly of α-SiC(6H), ZrB₂ and In Situ YAG(A1?Y₃O₁₂). The relative density, flexural strength, Young's modulus and vicker's hardness showed the highest value of 89.02[%], 81.58[㎫], 31.44[㎬] and l.34[㎬] for SiC-ZrB₂ composites added with 16[wt%] Al₂O₃+Y₂O₃ additives at room temperature respectively. Abnormal grain growth takes place during phase transformation from β-SiC into α-SiC was correlated with In Situ YAG phase by reaction between Al₂O₃ and Y₂O₃ additive during sintering. The electrical resistivity showed the lowest value of 3.14×10?²Ωㆍ㎝ for SiC-ZrB₂ composite added with 16[wt%] Al₂O₃+Y₂O₃ additives at 700[℃]. The electrical resistivity of the SiC-TiB₂ and SiC-ZrB₂ composite was all negative temperature coefficient resistance (NTCR) in the temperature ranges from room temperature to 700[℃]. Compositional design and optimization of processing parameters are key factors for controlling and improving the properties of SiC-based electroconductive ceramic composites.

무가압 어닐드한 SiC-TiB₂ 전도성 복합체의 특성에 미치는 In Situ YAG의 영향

辛龍德(Yong-Deok Shin),朱陳榮(Jin-Young Ju),高台憲(Tae-Hun Ko) 대한전기학회 2008 전기학회논문지 Vol.57 No.5

The composites were fabricated 61[vol.%] β-SiC and 39[vol.%] TiB₂ powders with the liquid forming additives of 8, 12, 16[wt%] Al₂O₃+Y₂O₃ as a sintering aid by pressureless annealing at 1650[℃] for 4 hours. The present study investigated the influence of the content of Al₂O₃+Y₂O₃ sintering additives on the microstructure, mechanical and electrical properties of the pressureless annealed SiC-TiB₂ electroconductive ceramic composites. Reactions between SiC and transition metal TiB₂ were not observed in the microstructure and the phase analysis of the pressureless annealed SiC-TiB₂ electroconductive ceramic composites. Phase analysis of SiC-TiB₂ composites by XRD revealed mostly of α -SiC(6H), β-SiC(3C), TiB₂, and In Situ YAG(Al?Y₃O₁₂). The relative density of SiC-TiB₂ composites was lowered due to gaseous products of the result of reaction between SiC and Al₂O₃+ Y₂O₃. There is another reason which pressureless annealed temperature 1650[℃] is lower 300-450[℃] than applied pressure sintering temperature 1950-2100[℃]. The relative density, the flexural strength, the Young's modulus and the Vicker's hardness showed the highest value of 82.29[%], 189.5[Mpa], 54.60[Gpa] and 2.84[Gpa] for SiC-TiB₂ composites added with 16[wt%] Al₂O₃+Y₂O₃ additives at room temperature. Abnormal grain growth takes place during phase transformation from β-SiC into α-SiC was correlated with In Situ YAG phase by reaction between Al₂O₃ and Y₂O₃ additive during sintering. The electrical resistivity showed the lowest value of 0.0117[Ω. ㎝] for 16[wt%] Al₂O₃+Y₂O₃ additives at 25[℃]. The electrical resistivity was all negative temperature coefficient resistance (NTCR) in the temperature ranges from 25℃ to 700[℃]. The resistance temperature coefficient of composite showed the lowest value of -2.3×10?³[℃]?¹ for 16[wt%] additives in the temperature ranges from 25[℃] to 100[℃].

모성 직업활동이 조산과 저체중출생 및 자연유산에 미치는 영향

신용덕,이태용,이영수,이동배 大韓産業醫學會 1994 대한직업환경의학회지 Vol.6 No.1

모성 직업활동이 조산, 저체중 출생아 및 자연유산에 미치는 영향을 알아보기 위해 1991년 1월부터 1992년 12월까지 대전에 위치한 C대학병원에서 출생한 1,646명의 산모를 대상으로 하여 조사한 결과는 다음과 같다. 1. 조사 대상자 1,646명의 산모중 임신중 직업을 가진 군이 20.3%, 직업을 갖지않은 군이 79.7%였으며, 직업여부의 분포에 통계적으로 유의한 차이를 보인 변수는 산모의 연령, 교육정도, 임신전 체중, 신장, 유산횟수였다. 2. 임신중 직업을 가진군의 평균 임신기관과 조산율은 39.1주, 7.8%였고, 비직업군은 39.0주, 9.7%였다. 직업군에서 평균 출산아 체중과 저체중 출생아율은 3.228g, 5.4%였고 비직업군은 3,140g, 10.6%였으며, 통계적으로 유의한 차이를 보였다(p<0.05). 평균 자연유산 횟수와 자연유산 경험율은 직업군이 0.2회, 15.0%, 비직업군이 0.3회, 17.4%였다. 3. 연령이 35세 이상, 미숙아 출산력이 있는 경우 및 유산횟수가 2회 이상인 경우는 직업군의 조산율과 저체중 출생아율이 비직업군에 비해 높았으나 통계적 유의성은 없었다. 산과적 합병증이 없는 경우 조산율이 직업군에서 비직업군보다 높았으나 역시 통계적 유의성은 없었다. 4. 자연유산 경험률은 연령이 35세 이상, 학력이 중졸 이하 및 고졸, 산모의 신장이 163cm이상에서 직업군에서 비직업군보다 높게 나타났으나, 통계적 유의성은 없었다. 5. 조산과 관련성이 있는 요인의 영향을 고려했을 때 직장활동군에서 조산의 위험도가 낮았으나 통계적 유의성은 없었다. 6. 임신주수 및 저체중 출생에 관련이 있는 요인의 영향을 고려한 후 직업군에서 저체중 출산의 위험도가 낮았으며 통계적 유의성을 보였다(p<0.05). 7. 과거 유산에 관련이 있는 요인의 영향을 고려한 경우 직업군에서 유산경험율이 낮았으나 통계적 유의성은 없었다. 8. 직업이 교사, 의료인, 은행원, 공무원인 군은 비직업군보다 조산율과 저체중 출생아율이 낮았으며, 회사원은 비직업군에 비해 조산율은 낮았으나 저체중 출생아율은 높았다. 상업군은 조산율과 저체중 출생아율이 15.2%로 비직업군 및 다른 직업군보다 비교적 높았다. 유산경험율은 은행원, 의료인,공무원에서는 비직업군의 17.0%보다 낮았으나, 교사군과 회사원은 17.8, 17.9%로 높았고, 상업군은 33.3%로 다른 직업군에 비해 현저히 높았으며 비직업군에 비해 교차비가 1.42로 통계적 유의성이 있었다(p<0.05). To investigate the effect of maternal job activity on the preterm delivery, low birth weight infant and spontaneous abortion, 1646 delivery data were analyzed from Jan. 1991 to Dec. 1992 in Chungnam University Hospital. The results obtained were as follows; 1. The percentage of subjects who had job during pregnancy was 20.3% and the variables of maternal age, education level, prepregnancy weight, maternal height, number of abotion showed significant difference in the distribution of subjects whether they had job or not. 2. There were no significant difference between the group who had job during pregnancy and those who had no job in the mean gestational period, number of spontaneous abortion, rate of preterm delivery and spontaneous abortion. However mean birth weight and rate of low birth weight showed significant difference between the groups. 3. The rate of preterm delivery of the group who had job were higher than those who had no job activity in the subgroup of 35 years or more age, prematurity history presence, 2 or more abortion history, obstetric complication presence, but there were no significant difference. The rate of low birth weight also higher in the group who had job than those who had no job activity in the same subgroup except obstetric complication presence. 4. The rate of spontaneous abortion of the group who had job were higher than those who had no job activity in the subgroup of 35 years or more age, below high school, height of 163cm or above, but there were no significant difference. 5. Rate of preterm delivery still showed better results in the group who had job than the group who had no job when adjusted for variables related, but there was no statistical significance. 6. Rate of low birth weight still showed better results with statistical significance in the group who had job than the group who had no job when adjusted for variables related. 7. Spontaneous abortion had occured less frequently in the group who had job than the group who had no job when adjusted for variables related. 8. Rate of preterm delivery and low birth weight were lower in the group of teacher, bank clerk, medical personnel, citizen servant than the group who had no job, but higher in the job of company employee, commerce. Spontaneous abortion was most frequent in group of commerce, and the group of teacher, company employee showed higher rate of abortion than the group who had no job.

식품의 치아우식유발지수측정법 개발에 관한 연구

신승철,마득상,박덕영 단국대학교 치과대학 예방치과 1998 예방치과 세미나집 Vol.- No.12

The purpose of this study was to evaluate the reliability of the method for assessing cariogenicity of foodstuffs using pH drop by S. mutans, S. mutans was cultured with 8 ml of Tood-Hewitt broth for 7 hours. Then, this broth was centrifuged and 7 ml of supematant was removed and 1 ml of bacterial pellet was remained. Each 1 ml of 0.1%, 0.5% and 0.1% sucrose solution as the experimental groups and distilled water as a control group were mixed with these remained bacterial pellet and cultured at 37℃. The pH was measured at each 10 minutes for 2 hours. The caries potential index(CPI) was measured by calculating the width of area below pH 5.7 line. The reliability of the method was evaluated by comparing coefficients of variation of CPI. As the results, with concentration of sucrose solution between 0.1% to 1.0%, the method assessing CPI using S. mutans discriminated each CPI of solutions fairly well and was reliable.

대량재해에 있어 미토콘드리아 DNA의 다형성을 이용한 개인식별

이숭덕,김기범,이윤성,최영태,신창호,이정빈 大韓法醫學會 1996 대한법의학회지 Vol.20 No.1

The mitochondrial DNA(mtDNA) is a small extranuclear DNA molecule that has been sequenced in man. the mtDNA has distinct characteristics over nuclear DNA. First, the evolutionary rate of nucleotide substitution appears to be larger compared with the nuclear DNA. Second, mtDNA is maternally inherited, so the determination of the various haplotype is unequivocal and no recombination has to be involved. Third, there is a 1.1 kb long control region, which shows severe polymorphism. These characteristics have been applied for several evolutionary study. Furthermore, they exist in cytoplasm with numerous copy number and their size, 16,569 bp is small relative to nuclear DNA, so they are more resistant to degradation or can be types in samples with only cytoplasm such as hair shaft without hair root. These presented the possibility of mtDNA as a tool in individual identification, especially when the nuclear DNA be unavailable. Actually, polymorphism in control region has been applied to individual identification for the skeletal remain found in Vietnam war. So we decided to apply the polymorphism of mtDNA in control region for the individual identification in case of mass disaster-"Downfall of Sampoong Department". Human remains from total 27 different individuals and 178 control persons were submitted for the individual identification. As the mtDNA comparison could be done through maternal lineage, 12 individual from 9 families from the control group were ruled out, because these families were consisted of father or were seeking for their father. Sequencing for the mtDNA control region was done using ABI automatic sequencer and DyeDeoxy Terminator Cycle Sequencing Kit. For convenience, sequencing reaction was done for two separate control region, region I from 16016-16401 in Anderson sequence, and regionⅡ from 048-388. First, sequences in regionⅡ of all samples and control persons were compared, and 20 samples were ruled out with no identical sequences in control group. Remaining 7 samples showed identical sequences with some of the control persons in three groups, and these identical pairs underwent mtDNA region I study. After region I study all samples except two dropped out in blood relationship. For the confirmation, STR and VNTR study such as MCT118, apoB, YNZ22, vWF, MBP, D21S11, TC-11 were done for remaining the two samples. The result denied the blood relationship between these two samples and any of the control group.

다량재해에 있어 미토콘드리아 DNA의 다형성을 이용한 개인식별 : 삼풍백화점 사건에 대하여

이숭덕,신창호,김기범,최영태,이윤성,이정빈 內務部 國立科學搜査硏究所 1996 國立 科學 搜査 硏究所 年報 Vol.28 No.-

우리나라 製造企業의 開途國 海外直接投資 進出協商에 관한 硏究 : The Entry Negotiations of Foreign Direct Investment in LDCs by Korean Manufacturing Firms

李永德,辛秀慶 충남대학교 경상대학부설 경영경제연구소 1991 경영논집 Vol.7 No.2

영지(Ganoderma lucidum)균사체의 액체배양에 의한 세포외 수용성 다당류의 분획 및 항암활성

이신영,강태수,문순옥,류인덕,이명열 한국미생물생명공학회 ( 구 한국산업미생물학회 ) 1996 한국미생물·생명공학회지 Vol.24 No.4

영지 균사체의 액체배양에 의하여 생산된 세포외 다당 시료를 분획하였고, 이들 각 분획에 대한 항암 활성을 균사체 유래 다당 분획들과 비교하면서 조사하였다. 배양여액으로부터 세포외 수용성 다당(BWS)을 얻었고, 이를 순차적으로 이온교환 및 겔 크로마토그라피 하여 BWS를 포함한 세포의 수용성 다당 분획, 총 5종을 얻었으며, 균사체 유래의 수용성 다당(MWS)에서도 세포외 다당과 동일한 방법으로 분획하여 총 5종의 분획을 얻어 대조구로 시용하였다. 세포외 다당 시료들의 항보체 활성(ITCH_50, %)은 15~30% 정도로 15~70%인 균사체 유래 다당 분획들의 값보다는 낮았으나, 이들 세포외 다당 분획들의 값보다는 낮았으나, 이들 세포외 다당 분획들중, BWS-DA와 BWS-DA-GI는 1000 ㎍/ml의 시료 농도에서 30% 정도의 매우 높은 활성을 나타내었다. MTT assay에서는 mouse leukemia L1210에 대하여 BWS-DN 및 MWS가 600㎍/ml의 농도에서 각각 86 및 89%의 높은 저해율을 나타내었으며, BWS-DA 및 MWS-DN의 경우는 3㎍/ml의 매우 낮은 농도에서도 32~35%의 저해율을 보였다. 또 human cell line인 COLO-205에 대해서는 BWS와 BWS-DA 및 MWS-DA가, 그리고 HL-60에 대해서는 BWS-DA와 BWS-DN 및 MWS-DN이 각각 300㎍/ml의 시료 농도에서 약 50%(IC_50)의 높은 저해능을 나타내었다. Exo-polysaccharide (BWS) obtained from submerged cultivation of Ganoderma lucidum mycelium was fractionated. Antitumor activity of their fractions was investigated in comparison with the mycelial polysaccharide fractions. Eight kinds (BWS-DN, BWS-DA, BWS-DN-GI, BWS-DA-GI, MWS-DN, MWS-DA, MWS-DN-GI and MWS-DA-GI) of polysaccharide fractions were obtained by DEAE-cellulose ion exchange chromatography and Sepharose CL-4B gel chromatography from BWS and MWS, which were isolated from culture fluid and mycelial cell, respectively. The anticomplementary activities (ITCH_50, %) of the exo-polysaccharide fractions showing 15% to 30% were lower than those of mycelial polysaccharide fractions showing 15% to 70%. The acidic fractions of BWS-DA and BWS-DA-GI fractionated from BWS, showed the highest activity of 30%. In the MTT assay, BWS-DN and MWS against mouse leukenia L1210 exhibited high inhibition ratio of 86 and 89%, respectively at the concentration of 600 ㎍/ml. High inhibition ratio of 50% (IC_50) was achieved for BWS, BWS-DA and MWS-DA fractions against human colon adenocarcinoma COLO-205 and for BWS-DN, and MWS-DN fractions against human leukemia HL-60 at the concentration of 300 ㎍/ml among the six polysaccharide fractions, respectively.