β-seed 첨가량 변화에 따른 질화반응 Si₃N₄의 특성변화

문지훈,최용규,이주신 경성대학교 2001 論文集 Vol.22 No.1

The effect of seeding on microstructure development and mechanical properties of reaction-bonded silicon nitride was investigated by the use of β-Si3N4 particles. The seeding of an appropriate amount of β- Si3N4 particles gave rise to the promotion of density and the resulting increase of fracture strength and hardness. And also, fracture toughness increased due to the development of elongated grains. On the other hand, addition of large amount of seed particles showed lower strength and facture toughness owing to the coalescence of large elongated grains. By seeding of 2wt% β- Si3N4 particles on Si powders of 7 μm, high fracture strength of 1100MPa and fracture toughness of 7.2MPa·m½ were obtained in reaction-bonded silicon nitride ceramics.

20km와 150km의 도로싸이클 주행이 혈중 렙틴, 지질과 호르몬 수준에 미치는 영향

최용어,권봉안,오재근,김범수,조준용,김문희 한국체육대학교 체육과학연구소 2000 韓國體育大學校附屬 體育科學硏究所論文集 Vol.19 No.1

Serum leptin, glucose, lipid profiles (free fatty acid, triglyceride, total cholesterol) were determined in two groups of subjects undergoing long and short strenous cycle race, 8 men who fasted overnight and then pedaled 20km cycle race and 8 men, 150km cycle race, respectively, Blood samples were collected before race, immediately after cessation of race and 2hr, 6hr after the end of race period. Cyclist pedaling 20km cycle race and cyclist pedaling 150km cycle race showed no statistical differences in leptin level. After 6hr of rest, leptin concentrations were gradually decreased but showed no statistical different in both groups. Epinephrine (p〈.01) and norepinephrine (p〈.001) concentration in comparison to pre-race levels were increased significantly. But insulin concentration in comparison to pre-race levels were decreased significantly (p〈.001). Glucose (p〈.01), free fatty acid (p〈.001), cholesterol (p〈.001) and triglyceride (p〈.01) were increased immediately after cessation of race in both groups.

77K에서 SC(NH₂)₂의 ¹⁴N 핵사중극 공명연구

최숙자,박영민,박현진,전인,송승기,서용문 명지대학교 자연과학연구소 1997 자연과학논문집 Vol.16 No.-

강유전체 질소화합물 thiourea [SC(NH₂)₂]분말시료의 ??plused NQR 실험을 77K 에서 실행하여 공명진동수와 핵사중극 결합상수, 비대칭인자, 완화시간등을 측정했으며, 4개의 공명선이 관측되었다. 결정내에는 주위 환경이 다른 두 종류의 질소 N₁,N₂가 존재함을 알 수 있었다. N₁에 관한 공명진동수는 ??(1)=2.6487㎒, ??(1)=2.032㎒, N₂에 대하여는 ??(2)=3.1852㎑, ??(2)=2.0183㎒이고, 공명선폭은 ??(1)=2.6752㎑, ??(1)=3.1852㎑, ??(2)=3.2618㎑, ??(2)=3.5448㎑ 임을 보였다. 한편 e²qQ/h의 값은 ν(1)에서 3.1205㎒, η는 0.3953이었으며, ν(2)에서는 3.0279㎒, 0.3939이었다. 이는 이미 보고된 결과와 일치하였다. 그리고, FID(Free Induction Decay)와 spin-echo실험을 통하여 얻은 스핀-격자 완화시간 T₁은 ??(1)에서 7.143 s, ??(2)에서 5.88 s이었으며, 스핀-스핀 완화시간 T₂는 ??(1)에서 25㎳, ??(2)에서 33.3㎳, ??(2)에서 33.3㎳의 값을 얻었다. We have measured ??N NQR frequencies, nuclear quadroupole coupling constants, asymmetric parameters and relaxation times in ferroelectric nitrogen thiourea [SC(NH2)2] at 77K, and four NQR resonance lines were observed. The results of measurements show that there are two kinds of nitrogen site, N1 and N2, with different environments in the crystal. The resonance frequencies were found to be ν+(l)=2.64 87MHz, ν_(1)=2.032 MHz for N1 and ν+(2)=2.6285MHz, ν_(2) =2.0183MHz for N2 respectively. The corresponding linewidths were ν+(1)= 2.6752kHz, Δν_(l) =3.1852kHz, ν+(2) =3.2618kHz and Δν_(2) =3.5448kHz, respectively. For N1, e2Q/h is 3.1205 MHz and η is 0.3953, and for N2, these are 3.0979MHz and 0.3939. These results are in agreement with those reported previously. The spin-lattice relaxation time (Ti) and the spin-spin relaxation time (T2) by FID and spin-echo experiments are as follows : T1(ν+(1)) is 7.143 s and T1(ν+(2)) is 5.88 s. T2(ν+(1)) is 25 ms, T2(ν_(1)) is 25 ms, T2(ν+(2)) is 33.3 ms and T2(ν_(2)) is 33.3 ms.

기어가 부착된 회전축계의 연성진동

최용문,손종동,윤한익 東義大學校産業技術開發硏究所 1992 産業技術硏究誌 Vol.6 No.-

The coupled effect on natural frequencies of Rotor System is studies by transfer matrix method. The results of this study are summarized as follows; (1) In case of coupled longitudinal vibration with flexural vibration the coupled effect of longitudinal vibration were 11.76% in comparison with first natural frequency of flexural vibration, 10.44% in comparison with second natural frequency, 3.1% in comparison with third natural frequency and 4.25% in comparison with fourth natural frequency. (2) In case of coupled longitudinal vibration with torsional and flexural vibration the coupled effects were almost same above. (3) It is found that the coupled effect have an influence on the mode shapes of flexural vibration.

표피낭종에 발생한 전염성 연속종 1예

문지훈,문용주,최혜자,윤석권 대한피부과학회 2003 대한피부과학회지 Vol.41 No.6

We present an unusual case of molluscum contagiosum occurring in epidermal cyst on back of a 5-year-old girl. Histology showed an intradermal cyst containing lamellated horny materials and typical molluscum cclls. In Korean literature, 5 such case were reported. We report an additional case of molluscum occurring in epidermal cyst. (Korean J Dermatol 3003;41(6) : 790~792)

大學 Elite選手들과 一般學生들의 情報化 實態에 關한 硏究

安文容,安孝爵,崔忠煥 한국체육대학교 학생생활연구소 1997 學生生活硏究 Vol.- No.3

The conclusion below shows how elite athletes in college met information through the mass media and computer usage. These results were obtained by surveying 100 elite athletes in college, 100 students in college of liberal arts and 100 students in college of science from university in Seoul. 1.It is T.V that elite athletes've used most frequently as an information sourtce, while newspaper's played an important role as an information source to students of college of liberal arts and science. 2.Many students(elite athletes 56%, students in college of liberal arts 40%, students in college of science 36%) have thought they've had insufficient informations. 3.They've mostly enjoyed reading spots section in newspaper and eagered for getting informations about self-development and qualification certificate. 4.There have been elite athletea(48%) who didn't read the newspaper and also students in college of science(12%) who didn't watch T.V. 5.They've enjoyed soap opera most of all and hardly watched cultural program 6.They(elite athletes 50%, students ill college of liberal arts 82%, students in college of science 84%) almost have personar computers but they've not read books regarding computer. 7.There were some elite athletes(34%) who didn't know at all how to use computer and they(57%) didn't use computers at all even once a day. 8.Almost of them(elite athletes 92%, students in college of liberal arts 75%, students in college of science 94%) have had beepers, but they've(elite athletes 77%. students in college of liberal arts 85%, students in college of science 86%) not had cellular phone let. And they've(elite athletes 38%, students in college of liberal arts 49%, students in college of science 44%) believe that Korea will be a full intelligence society after ten years.

직접 분사식 가솔린 엔진의 분사 조건 변화에 따른 실린더 내 분무 유동 특성에 관한 연구

전문수,장광진,황용하,최원호 忠州大學校 2005 한국교통대학교 논문집 Vol.40 No.2

This study presents the spray characteristics of high pressure swirl type gasoline injector for the application of direct-injection gasoline engine. For the purpose, Mie seattering technique and the PDPA(Phase Doppler Particle Analyzer) measurements were used for the fundamental spray characteristics, In-cylinder spray flow motion was also visualized in order to optimize combustion system of the engine. Various fuel injection conditions such as intake flow condition, different combustion chamber shape, fuel injection timing, and engine speed were considered to obtain the detailed in-cylinder spray characteristics by use of ICCD(Intensified Charge Coupled Device) camera through the single-cylinder potical engine. From the experimental results, the test injector shows a good low-end linearity between the dynamic flow and fuel injection pulse width and the fuel spray of 20mm or less in SMD(Sauter Mean Diameter) with good spray symmetry. In addition, the in-cylinder tumble flow has more effect on the homogeneous mixture formation than that of in-cylinder swirl flow at early injection mode and the in-cylinder swirl flow plays a better role of stratified mixture preparation than tumble flow at late injection mode.

數理的 外揷法에 의한 韓國의 人口豫測 模型에 관한 硏究

김용문,최종석 충남대학교 자연과학연구소 1993 忠南科學硏究誌 Vol.20 No.1

In the paper, a study on Korea Population Predictive Model by the Method of Mathematical Extrapolation is based on Logistic Curve and Gompertz Curve. Data used census data from 1955 to 1990. But census is not usually done punctually. So we try to use the raw census data and correct them by approprate transformation. We can guess Population Predictive Medel and Increasing Rate and Transition point and Saturation Population. Logistic Curve and Gompertz Curve estimated model optimum curve by the Method of Mathematical Extrapolation.

여의도 성모병원 신경정신과 입원환자에 대한 통계학적 고찰

김종은,최수호,최보문,김용찬,이규환 최신의학사 1984 最新醫學 Vol.27 No.1

서중조건하에서의 콘크리트 충전 강관 기둥의 시공을 위한 실험적 연구

이장환,강용학,정근호,김진호,최문식,정상진 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1(구조계)

The basic Physical properties, Slump, Slump flow, Air content, Bleeding, and Settlement of concrete was investigated to test Characteristic of Setting and to evaluate the relation between Model specimen and Heat of hydration for construction Over the High Temperature(CFT). The objective of this study is to take the partial core after the cementation of Model specimen, test the compression intensity and analyze the relation to Test piece.