• 청정기술
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• 제28권2호
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• pp.103-109
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• 2022

Nd-Fe-B 폐영구자석 스크랩에는 희토류가 약 20~30% 함유되어 있고 철이 약 60~70% 함유되어 있으며, 황산침출 및 분별결정법을 통하여 희토류 및 철 성분을 회수하고자 하였다. 희토류와 철을 분리·회수하기 위하여 산화배소를 하지 않고 황산농도 및 광액농도비를 변수로 하여 침출특성을 확인하였다. 황산침출은 농도별로 3시간 동안 침출을 진행하였고 침출된 고상을 X-ray diffraction (XRD) 및 XRF (X-ray florescence spectrometry) 분석으로 결정상 및 조성 및 정량적 성분을 확인하였으며, 여액은 ICP 분석을 시행하였다. 3M 황산농도에서 침출했을 경우 네오디뮴 황산화물로 형성되었고 철 성분이 가장 적으며 회수율이 높았다. 남은 여액은 증발농축을 통하여 분별결정법을 하였으며 네오디뮴 성분은 7.0배 농축되었고 철 성분은 2.8배 농축되었다. 본 논문에서 폐영구자석의 산화배소 공정단계 없이 황산침출 및 분별결정법을 통한 희토류 성분의 회수율은 약 99.4%로 확인되었다.

• 한국결정성장학회지
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• 제9권1호
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• pp.119-125
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• 1999

본 연구는 싸이클론 반응로에서 $FeS_{2}$의 반응 특성에 관한 조사를 연구하였다. 수학적인 모형도로 이 반응로에서 $FeS_{2}$의 oxidation과 suifation 등을 전개하엿다. 모형은 $FeS_{2}$에서 chemical control shrinking core로서 그리고 ${Ca(OH)}_{2}$에서 fluid film control shrinking core로서 가정하였으며 수식으로서 발전시켰다. 본 실험은 이 반응 파라메터들의 영향에 연구로서 진행하였으며 즉 반응로의 온도변화, $FeS_{2}$의 입자크기, 공기 주입비율, 시료 주입비율, 그리고 $FeS_{2}$와 ${Ca(OH)}_{2}$ 비율 등이다. Oxidation과 Sulfation에 의한 반응물들은 화학적 및 물리적으로 특성을 기술하였다.

• 한국재료학회지
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• 제15권5호
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• pp.313-317
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• 2005

The relation between bulk microdefect (BMD) and mechanical strength of $P/P^-$ epitaxial silicon wafers (Epitaxial wafer) as a function of nitrogen concentrations was studied. After 2 step anneal$(800^{\circ}C/4hrs+1000^{\circ}C/16hrs)$, BMD was not observed in nitrogen undoped epitaxial silicon wafer while BMD existed and increased up to $3.83\times10^5\;ea/cm^2$ by addition of $1.04\times10^{14}\;atoms/cm^3$ nitrogen doping. The slip occurred for nitrogen undoped and low level nitrogen doped epitaxial wafers. However, there was no slip occurrence above $7.37\times10^{13}\;atoms/cm^3$ nitrogen doped epitaxial wafer. Mechanical strength was improved from 40 to 57 MPa as nitrogen concentrations were increased. Therefore, the nitrogen doping in silicon wafer plays an important role to improve BMD density, slip occurrence and mechanical strength of the epitaxial silicon wafers.

• 한국염색가공학회지
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• 제6권2호
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• pp.47-54
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• 1994

Cotton fiber, NaOH-mercerized cotton fiber, cotton fabric, and NaOH-mercerized cotton fabric have been treated by liquid ammonia at -33.4$^{\circ}C$. The fine structures, bending properties, tensile strengthes, shrinkages for laundering, and wrinkle recoveries were studied. The treatment of cottons with liquid ammonia brought about the transition of crystal lattice ; transforming cellulose I crystal of original cotton to cellulose I and III crystal, and cellulose II crystal of mercerized cotton to cellulose II and III crystals. The degree of crystallinities were decreased in the order of liquid ammonia>NaOH/liquid ammonia>NaOH-treated cotton. However moisture regain and water absorbency for liquid ammonia-treated cotton were lower than that of NaOH-treated cotton because of a difference in swelling actions of the agents. It seems caused by intermicrofibrillar pores produced in swelling processes. The bending rigidity and bending hysteresis were decreased remarkly by liquid ammonia treatment. Therefore softness and dimensional stability were improved. The liquid amminia and NaOH/liquid ammonia-treated cottons moreover show excellent properties in tensile strength, anti-shrinkage for laundering, and wrinkle recovery.

• 한국어정보학회:학술대회논문집
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• 한국어정보학회 2016년도 제28회 한글및한국어정보처리학술대회
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• pp.226-230
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• 2016

본 연구는 초등 저학년 읽기부진아동을 위한 한글 파닉스 교육의 기반을 확립하고자 1-2학년 교과서 고빈도 어절 531개를 기반으로 자소 및 음운규칙을 분석하였다. 연구결과, 자소-음소 일치 어절을 기반으로 하였을 때 초성에서 50번 이상 나타난 자소는 /ㄱ/, /ㄹ/, /ㄴ/, /ㅅ/, /ㅎ/, /ㅈ/이다. 중성에서 50번 이상 나타난 자소는 /ㅏ/, /ㅣ/, /ㅗ/, /ㅡ/, /ㅜ/이다. 종성에서 50번 이상 나타난 자소는 /ㄹ/, /ㄴ/, /ㅇ/이다. 자소와 음소가 불일치 된 어절을 기반으로 하였을 때 가장 많이 출현하는 음운규칙은 연음화 규칙이었다. 본 연구결과를 바탕으로 교과서를 기반으로 한 한글 파닉스 교육에 유용하게 사용될 수 있을 것이다.

• 한국염색가공학회지
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• 제4권2호
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• pp.76-83
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• 1992

Wool tropical and nylon taffeta were treated with low temperature plasma of $O_2$, $N_2$, NH$_3$, CF$_4$ and CH$_4$ for the intervals of 10 to 300 sec, and then dyed with leveling and milling type acid dyes in presence or absence of buffer solution. From the color depth of dyed fabrics, effect of plasma gases, treated time, dyeing time and temperature on dyeing property was studied. The results of the experiment can be summarized as follows: 1) The plasma treatments except methane gas increased the color depth of dyed wool fabrics, but not that of dyed nylon fabrics regardless of the plasma gases used. 2) The color depth of wool fabrics dyed in the dye bath without buffer solution was increased by the low temperature plasma, especially increased much more by CF$_4$ plasma treatment. It is found that with the identification of F- ion in the residual dye bath the hydrogen fluoride gas was adsorbed on wool fabrics in the plasma treatment. 3) The color depth of wool fabrics was increased with the time of $O_2$ and CF$_4$ plasma treatments. 4) In both cases of the leveling and milling type acid dyes, the rate of dyeing was increased in the low temperature plasma treatments, and it is found that the leveling type acid dye increased the color depth at relatively low temperature below 4$0^{\circ}C$, compared with the milling type acid dye.

• 한국광학회지
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• 제9권3호
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• pp.175-180
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• 1998

고체 레이저매질로 가장 널리 쓰이는 Nd:YAG 단결정을 Czochralski 방법으로 육성하였다. 자체 제작한 Czochralski 결정 육성로 및 자동 결정 적경제어 장치를 써서 유효 직경 50mm, 길이 100mm의 Nd3+ 이온농도가 0.9at%이고 <111>방향의 단결정을 육성하였다. 단결정 육성시 융액의 수직방향에 대한 온도구배가 중용한 변수인 것이 확인되었으며, 결정 직경은 자동 제어가 가능하도록 컴퓨터 프로그램을 제작하였다. 육성된 단결정을 절단, 가공, 연마, 코팅 과정을 거쳐서 레이저 발진용 Nd:YAG막대를 제작하고 흡수 스펙트럼, 형과 스펙트럼 분석을 통하여 정확한 Nd:YAG의 레이저 발진특성을 확인하였다. 자체 가공된 레이저 막대로부터 발진된 CW 레이저의 최대 출력은 70W이었고, 발진문턱값과 효율은 각각 1.3kW, 1.64%이었다.

• KIEAE Journal
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• 제8권2호
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• pp.65-70
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• 2008

Recently, there has been growing interest in barrier-free design which makes safe and convenient space for every pedestrian, not only the non-disabled but also the disabled. The purpose of this study is to suggest the data on the pavement materials of barrier-free pedestrian environment in view of universal design. In order to this, the research is focused on evaluating the visual preference and preference factors for pavement scenery, which can be changed by pavement materials. And this research is also comparing the visual preference and preference factors of the disabled with that of the non-disabled. A multi-regression analysis method is adopted to analyse the correlation between the visual preference for pavement scenery and preference factors in this study. The result of this analysis is as follows. Firstly, there are some differences of visual preference for the pavement material between the disabled and the non-disabled. Secondly, independent variables influencing on preference are similar between two groups. Thirdly, there are some differences in the priority of preference between the disabled and the non-disabled. This study will contribute to the field of barrier-free design and sustainable development projects in order to maximize the human being's satisfaction.

• 음성과학
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• 제12권2호
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• pp.139-149
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• 2005

The purpose of this study was to propose a preliminary norm for 'Korean-Test of Articulation for Children(K-TAC)'. The K-TAC was designed to test 19 Korean consonants in various phonetic contexts through 37 words. We collected the data of 220 normally developing children aged 2;6(years;months) to 6;5. We analyzed the mean percentage of consonants correct and the age of acquisition for K-TAC. The results were as follows: first, The mean percentage was over 60% at late 2 years of age, over 80% at th age of 3, and over 90% after the age of 4. There were significant differences among age groups. Second, based on the criterion of correct production by 75% of children, Korean children acquired stops and nasals except for SF velars, glottal fricative, SF liquid and affricates by late 2 or 3 years of age. After that they acquired SF velars at the age of 4 and SI liquid at the age of 5. However, they could not acquire alveolar fricatives by the age of late 6. Third, if the distorted sounds were scored as correct, they acquired SI liquid at 4 years of age and alveolar fricatives at 5 years of age.

• 음성과학
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• 제7권2호
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• pp.37-50
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• 2000

This paper describes a test of everyday speech understanding ability, in which a listener's utilization of the context-situational information of speech is assessed, and is compared with the utilization of acoustic-phonetic information. The test items are sentences which are presented in a babble type of noise, and the listener response is the key word in the sentence. The key words are always two-syllabic nouns and the questioning sentences are added to obtain the responding key words. Two types of sentences are used. One is the high-predictable sentences for which the key word is somewhat predictable from the context. The other is the low-predictable sentences for which the key-word cannot be predicted from the context. Both types are included in six 40-item forms of the test, which are balanced for intelligibility, key-word familiarity and predictability, phonetic content, and length. Performance of normally hearing listeners shows significantly different functions for various signal-to-noise ratios. The potential applications of this test, particularly in the assessment of speech understanding ability in the hearing impaired, are discussed.