• 열처리공학회지
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• 제6권1호
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• pp.1-8
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• 1993

In this paper, the surface roughness influenced by Sm45C hardness in high frequency induction hardening and mechanical characteristics for the changed Hv 598 part and the unchanged hardness Hv 223 part by use of cermet and ceramic cutting tools was experimentally examined. Finally, we could be had some important results by processing surface roughness on cutting conditions such as cutting speed, feed rate, depth of cut and changes of tool nose radius. The results are summarized as follows. 1. In case of the same cutting condition, the hardness of workpiece was high and acquired the best processing surface roughness when the radius of the tool nose had 0.8 mm and feed rate was 0.04 mm/rev. 2. In case of the hardness of workpiece, though the cutting speed didn't have an effect on processing surface roughness, the less feed rate and the more processing surface roughness improved. On the other hand, the low inside the hardness of workpiece, the more cutting speed and the more feed rate increase, the processing surface of roughness improved. 3. Regardless of the hardness of workpiece, the change of the cutting depth didn't have great effect on the surface roughness. 4. On cutting the high surface hardness part with cutting tools of cermet and ceramic, it can be acquired the higher processing surface roughness because it hadn't been taken effect on cutting speed, In case of the cutting process of the low inside hardness part the two cutting tools have acquired the similar processing surface roughness.

• 응용통계연구
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• 제35권2호
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• pp.251-263
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• 2022

제1상 임상시험은 '투약 용량 발견 시험(dose finding study)'라고도 불리는데 동물 실험 또는 시험관 실험을 통하여 개발된 신약 물질을 사람에게 시험하는 첫 단계이다. 제 1상 임상시험의 목적 중 하나는 환자에게 허용할 수 있으면서 최대의 효능을 가진 복용량인 최대허용용량(maximum tolerated dose, MTD)을 결정하는 것이다. 본 논문에서는 다양한 멈춤 규칙을 이용한 MTD 추정법들을 소개한다. 또한 모의실험을 통해 SM3, NM, Rim, J3, BSM 방법을 비교하고 효율적인 MTD 추정법에 대해 고찰한다. 모의실험 결과 BSM방법이 목표독성확률에 가장 가깝게 MTD를 추정하는 것으로 나타났다. 또한 J3방법의 피험자 수가 가장 적었다. 이러한 결과는 두 방법의 멈춤 규칙의 특성 때문이라고 판단되는데 BSM방법은 독성 반응이 있을 때 같은 용량에 피험자를 2명 또는 1명을 추가한다. 또한 J3방법은 동일한 용량에 할당되는 최대 피험자 수가 다른 방법에 비해 적다. 이러한 특성들을 결합하여 추정법을 개선한다면 더 효율적으로 MTD를 추정할 수 있을 것이다. 특히 BSM방법의 멈춤 규칙을 이용하면서 총 피험자 수를 줄일 수 있다면 적은 수의 피험자로 정확한 추정이 가능할 것이다.

• 대한화학회지
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• 제43권6호
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• pp.628-635
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• 1999

활성화된 $Mn(IV)O_2$를 이용하여 2,6-bis(hydroxymethyl)-4-methylphenol로부터 2,6-diformyl-p-cresol과 2-hydroxy-3-hydroxymethyl-5-methylbenzaldehyde를 제조하였다. 2-hydroxy-3-hydroxymethyl-5-methylbenzaldehyde와 ethylenediamine 및 1,3-diaminopropane의 축합반응에 의해 6-배위 칸막이 리간드, $H_4L[A]와\; H_4L[B]$를 각각 얻었다. methanol에서 2,6-diformyl-p-cresol과 1,2-diaminobenzene으로부터 부분적으로 환원된 거대고리, $H_4[20]DOTA$를 얻을 수 있었다. 이 $H_4[20]DOTA$와 lanthanide(IlI) nitrate 간의 반응 또는 methanol에서 주형과정(template procedure)에 의해 일핵 착물, $[Ln(IIl)(H_2[20]DOTA)(ClO_4)(H_2O)]\;{\cdot}\;3H_2O과\; [Ln([20]DOTA)(NO_3)(H_2O)](NO_3)_2\;{\cdot}\;xH_2O$를 각각 합성하였다. $[Ln([20]DOTA)(NO_3)(H_2O)](NO_3)_2\;{\cdot}\;xH_2O$를 2일 정도 methanol에 정치함으로써 얻은 $[Ln([20]DOTA)(NO_3)(CH_3OH)]^{2+}$에서 배위된 $CH_3OH$이 주게원자가 O인 보조리간드, $L_a$(=salicylic acid, p-chlorobenzoic acid, benzoic acid, acetic acid, 4-bromophenol)에 의해 치환될 때 평형상수 (K)를 25$^{\circ}C$, ${\mu}$=0.1M $NaClO_4$에서 분광학적 방법으로 결정하였다. 이 때 평형상수(K) 값들은 보조리간드 pKa 크기의 반대 경향인 salicylic acid>p-chlorobenzoic acid>benzoic acid>acetic acid>4-bromophenol 순서로 나타났다.

• Tribology and Lubricants
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• 제22권5호
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• pp.282-289
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• 2006

This paper is to investigate the wear behaviors of two type ceramics, $Al_{2}O_{3}\;and\;TiO_{2}$, by coated plasma thermal spray method under the lubricative environment. The lubricative environments are grease fluids, a general hydraulic fluids, and bearing fluids. The wear testing machine used a pin on disk type. Wear characteristics, which were friction force, friction coefficient and the specific wear rate, according to the lubricative environments were obtained at the four kinds of load and sliding velocity is 0.2 m/sec. After the wear experiments, the wear surfaces of the each test specimen were observed by a scanning electronic microscope.

• 한국자기학회지
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• 제5권5호
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• pp.376-379
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• 1995

Employing the muffin-tin-orbital theory combined with pseudo-potential concepts, we have evaluated hybridization matrix elements between R and T sites in $RT_{2}$ compounds. The matrix elements are calculated with two parameters, the interatomic distance between R and T atoms from the crystal structure data, and the expectation values of the radial distances for the radial wave functions of the ground state charge densities, which are obtained from the linearized muffin-tin orbital band method within the local density approximation. It is found that the R 4f/T 3d hybridization matrix elements decrease with an increasing atomic number from R=Ce to Gd, and that they are smaller in $RNi_{2}$ than in $RCo_{2}$, which are consistent with trends observed in recent photoemission spectroscopy experiments. It is also found that the magnitudes of the hybridization matrix elements in $RFe_{2}$ are comparable to those in $RNi_{2}$.

• 한국양식학회지
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• 제20권2호
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• pp.140-143
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• 2007

우리나라 고유 담수 어종인 쉬리(Coreoleuciscus splendidus; Cyprinidae)를 대상으로 세포크기, 염색체 수 분석, 핵형 분석, 세포당 DNA 함량 조사 등 세포유전학적 연구를 실시하였다. 쉬리 암,수의 염색체 modal number는 모두 2n = 48로 나타났으나 암,수간 형태가 다른 성염색체(sex chromosome)가 관찰되었다. 쉬리 암컷은 10쌍의 중부염색체, 6쌍의 차중부염색체, 8쌍의 차단부염색체 그리고 XX 염색체로 나타났고, 반면 수컷은 10쌍의 중부, 6쌍의 차중부 및 8쌍의 차단부염색체와 함께 XY 성염색체를 나타냄으로써 전형적인 XX-XY의 성 결정 기작(sex determination mechanism)을 갖는 것으로 나타났다. 또한 쉬리는 1쌍의 Ag-NOR을 차단부 상동염색체에 갖고 있었고, 쉬리의 세포당 평균 DNA 함량은 flow cytometry 분석을 통해 2.4 pg/cell로 나타났다. 적혈구 세포 크기를 분석을 통해 핵 용적을 평가한 결과 암수 모두 $28\;{\mu}m^3$를 나타내었다. 본 세포유전학적 분석 결과를 통해 본 어종은 진화과정 중 여러 잉어과 어류에서 관찰되는 배수성에 의한 진화 보다는 유전자 재조합 등 점 돌연변이가 진화가 기본 기작이었을 것으로 판단된다.

• 한국환경과학회지
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• 제22권6호
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• pp.705-715
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• 2013

The response of the freshwater microalga Chlorella vulgaris to mercuric ion ($Hg^{2+}$) stress was examined using chlorophyll a fluorescence image analysis and O-J-I-P analysis as a way to monitor the toxic effects of mercury on water ecosystems. The levels of photosynthetic pigments, such as chlorophyll a and b and carotenoids, decreased with increasing $Hg^{2+}$ concentration. The maximum photochemical efficiency of photosystem II(Fv/Fm) changed remarkably with increasing $Hg^{2+}$ concentration and treatment time. In particular, above $200{\mu}M\;Hg^{2+}$, considerable mercury toxicity was seen within 2 h. The chlorophyll a fluorescence transient O-J-I-P was also remarkably affected by $Hg^{2+}$; the fluorescence emission decreased considerably in steps J, I, and P with an increase in $Hg^{2+}$ concentration when treated for 4 h. Subsequently, the JIP-test parameters (Fm, Fv/Fo, RC/CS, TRo/CS, ETo/CS, ${\Phi}_{PO}$, ${\Psi}_O$ and ${\Phi}_{EO}$) decreased with increasing $Hg^{2+}$ concentration, while N, Sm, ABS/RC, DIo/RC and DIo/CS increased. Therefore, a useful biomarker for investigating mercury stress in water ecosystems, and the parameters Fm, ${\Phi}_{PO}$, ${\Psi}_O$, and RC/CS can be used to monitor the environmental stress in water ecosystems quantitatively.

• 대한기계학회논문집
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• 제5권2호
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• pp.110-121
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• 1981

In order to study on the fracture behavior and the fracture thoughness of combined structure, the specimens, structural steel (SM28C) and 6:4 brass are annealed for ductility and investigated for the befavior of fracture and the absorbed energy at the variation of the impact velocity. The results obtained by this study are as follows: (1)The maximum load increases with the impact velocity, but in the condition of constant impact velocity it decreases as the ductility increases. (2)The absorbed energy increases with the impact velocity, but in the condition of constant impact velocity it is constant as the ductility increases. (3)In the case of the combined structure of peralite and ferrite, the microcracks initiates and propagates mainly in the ferrite structure intergranular in accompany with the slip, and the slip concentration phenomena occur in the boundary of pearlite structure However, in case of the combined structure of .alpha. and ..betha. phase, the microcracks initiates and propagares mainly in the .alpha. phase intergranularly, and slip concentration phenomena not ocur in the boundary of .betha. phase.

• 한국생산제조학회지
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• 제4권2호
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• pp.31-37
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• 1995

This study is focused on the prediction of appropriate tool life by clarifying the correlation between progressive tool wear and AE signal. when rcutting SM45C by End mill in machining center. First of all, end mill have a problem that position of sensor sticking because it is revolution tool, but I think that it can be bained specific character according to sticking Sensor in the Vise. Consequently, the following results have been obtained; 1. Each cutting speed of feed rate over 0.1mm had a tendency to increase linearly according to the RMSAE 2. The level of AE signal at the same cutting area was more sensitive to depth of cut tharn the variation of feed rate 3. In the range of cutting duringqr about 75minqr atqr cutting speed 27m/min flankqr wear turns up aboutqr 0.21mm, aboutqr 0.29mm in the caseqr of about 65minqr at 33/min, qr hereby RMSAE increased rapidly at 0.2mm flank wear, also AE-HIT and CUM-CNTS.

• 한국동물학회지
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• 제6권2호
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• pp.21-27
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• 1963

This study is concerned with alterations in chromosomes (numbers and morphology) when the culture of Chinese hamster cells (FAF-28 strain) was treated by steroids, testosterone and DOC. 1. In 200 cells of normal untreated cells as control population the chromosome of stemline was decided as which was contained in 158 cells ; that is , in 79 percent of the population. The average chromosome number in above 20 cells observed was calculated as 23.95 with minimum limit at 20 and maximum limit at 70. 2. Many different chromosome numbers, ranging from 19 to 352 were observed in the 200 cells treated by testosterone. The diploid number of 22 showed the peak of variation curve was counted in 71 cells (35.5%) and an average chromosome number of stemline was 22 which was counted in 74 cells (37%). While all of the chromosome number of stemline was 22 which was counted in 74 cells (37%). While all of the chromosome numbers in the 200 cells observed ranged from 20 to 181 , an average chromosome number was also found to be 30.09. 4. The chromosome component in the cultured normal FAF-28 cells with 22 diploid chromosomeswas as follows ; 9a) 2 paris were long and metacentric (LM), (b) 3 pairs were medium length and metacentric (MM), (c) 3 pairs were small and subtelocentric (SS) and (d) 3 pairs were small and metacentric (SM). 5. The twenty cells with 44 chromosomes were selected at random from each cell population treated with testosterone and DOC , so that chromosome idiogram and morphology could be studies. In the twenty cells of the testosterone treated population the average ratio of above four groups, LM ; MM;Ss:SM, was found to be 8.6 : 10.8:13.5:10.7. On the other hand, the average ratio in the same number of cells of the DOC treated one was 7.7 :11.4:12.5:12.7. 6. The five types of the altered chromosomes morphologically in the hundred cells selected at random from each cell population treated by testosterone and DOC were observed (Type I-V). The thirty-one altered chromosomes were found to be in the testosterone treated cell population and the sixteen in DOC treated.