• Communications for Statistical Applications and Methods
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• 제5권3호
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• pp.935-944
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• 1998

This paper investigates the problem of goodness of fit tests for no effect model. The proposed test statistic $Z_{mn}$ is obtained by multiplying constant on the model free curve estimation techniques. The small and large sample properties of$Z_{mn}$ are investigated and the good results of power studies for the proposed test are illustrated.

• 대한금속재료학회지
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• 제48권2호
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• pp.122-132
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• 2010

Higher strength and fracture toughness of reactor pressure vessel steels can be obtained by changing the material specification from that of Mn-Mo-Ni low alloy steel (SA508 Gr.3) to Ni-Mo-Cr low alloy steel (SA508 Gr.4N). However, the operation temperature of the reactor pressure vessel is more than $300^{\circ}C$ and the reactor operates for over 40 years. Therefore, we need to have phase stability in the high temperature range in order to apply the SA508 Gr.4N low alloy steel for a reactor pressure vessel. It is very important to evaluate the temper embrittlement phenomena of SA508 Gr.4N for an RPV application. In this study, we have performed a Charpy impact test and tensile test of SA508 Gr.4N low alloy steel with changing impurity element contents such as Mn and P. And also, the mechanical properties of these low alloy steels after longterm heat treatment ($450^{\circ}C$, 2000hr) are evaluated. Further, evaluation of the temper embrittlement by fracture analysis was carried out. Temper embrittlement occurs in KL4-Ref and KL4-P, which show a decrease of the elongation and a shifting of the transition curve toward high temperature. The reason for the temper embrittlement is the grain boundary segregation of the impurity element P and the alloying element Ni. However, KL4-Ref shows temper embrittlement phenomena despite the same contents of P and Ni compared with SC-KL4. This result may be caused by the Mn contents. In addition, the behavior of embrittlement is not largely affected by the formation of $M_3P$ phosphide or the coarsening of Cr carbides.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.369-372
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• 1996

We prepared LiMn$_2$O$_4$ by reacting stoichiometric mixture of LiOH.$H_2O$ and MnO$_2$ (mole ratio 1 : 1) and heating at 80$0^{\circ}C$ for 24h, 36h, 48h, 60h and 70h. We obtained through X-ray diffraction that lattice parameter varied as function of heat treatment time. heated cathode active materials at 80$0^{\circ}C$ for 36h, (111)/(311) peak ratio was 0.37. It expected good charge/discharge characteristics. When (111)/(311) peak ratio was 0.37, it will be that crystal structure is farmed very well. In the result of charge/discharge test When heated at 80$0^{\circ}C$ for 36h, charge/discharge characteristic of LiMn$_2$O$_4$is the most property. It agree with our expectation.

• 열처리공학회지
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• 제34권6호
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• pp.294-301
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• 2021

In the present study, we investigate the effects of long-term heat treatment at elevated temperatures on the mechanical softening of the Mn-Mo-Ni low-alloy steel. The influence of long-term heat treatment on microstructure and mechanical strength was evaluated. To simulate the long-term material degradation, heat treatment test was interrupted at several stages up to 10,000 hours in an electric furnace. The Mn-Mo-Ni low-alloy steel shows a typical bainitic phase, which consists of a well-developed lath substructure with fine precipitates along the lath boundaries. However, these fine precipitates were redissolved into the matrix with long-term heat treatment, and then the lath substructures were recovered. Consequently, ultimate tensile strength and yield strength decreased during long-term heat treatment showing a mechanical softening phenomenon.

• 한국자기학회지
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• 제11권4호
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• pp.141-145
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• 2001

Mn-Ir-Pt/Ni-Fe 교환이방성 이층박막은 계면에서 높은 교환결합자계(exchange bias field; $H_{ex}$)를 가질 뿐만 아니라 뛰어난 열적안정성과 Mn-Ir에 비하여 좋은 내식성을 나타내므로 스핀밸브형 다층막 소자의 고정층의 재료로 적합하다고 생각되어진다. 열적안정성에 관한 평가인 blocking 온도( $T_{b}$)는 Mn-Ir이 240 $^{\circ}C$로 Mn-Ir-Pt가 250 $^{\circ}C$로 Mn-Ir에 비하여 Mn-Ir-Pt의 $T_{b}$가 높은 것으로 평가되었으며, 내식성에 관한 평가인 부식전류밀도는 Mn-Ir-Pt 10배 정도의 낮은 값을 가지므로 내식성 또한 Mn-Ir에 비해 우수한 것으로 평가된다. Mn-Ir에 Pt를 약 1.9 at%정도 첨가하였을 때 $H_{ex}$가 가장 큰 값을 나타내었다. 본 연구에서 Ni-Fe/M $n_{78.3}$I $r_{19.8}$P $t_{1.9}$의 고정층을 사용한 스핀밸브 다층막의 자기적, 구조적 특성을 연구한 결과 약 5 %의 자기저항비를 얻을 수 있었다.다.다.다.다.다.다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.213-214
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• 2011

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.303-303
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• 2008

$LiMn_2O_4$는 출력특성이 좋고 가격이 저렴하지만 전해액 중에서 $Mn^{2+}$이 용출되어 나오는 것과 반복적인 충방전시 구조가 파괴되는 단점이 있어 이것을 보완하고자 $FePO_4\cdot2H_2O$를 $LiMn_2O_4$의 표면에 코팅하였다, $LiMn_2O_4$를 모재로, $FePO_4\cdot2H_2O$를 코팅재로 사용하여 $FePO_4\cdot2H_2O$의 코팅량 변화와, 열처리 온도변화에 따른 물성 변화를살펴보았다, LiOH 와 $MnO_2$의 혼합물을 $1000^{\circ}C$ 에서 소성하여 $LiMn_2O_4$를 합성하고, Fe$(NO_3)_3$ 수용액과 $NH_4H_2PO_4$ 수용액을 혼합하여 $FePO_4\cdot2H_2O$를 제조하였다, $LiMn_2O_4$에 $FePO_4\cdot2H_2O$를 1wt%, 2wt%, 3wt% 비율로 ball milling 을 통해 코팅한 후, 온도를 변화시키면서 열처리 하였다. 코팅한 물질을 XRD를 통해 구조를 분석하고 SEM을 이용하여 형상을 관찰하였다. 또한 고온에서의 $Mn^{2+}$의 용출량을 ICP로 측정하고 half-cell을 만들어 충방전 test를 통해 충방전 특성을 조사하였다. 아울러, 코팅량과 열처리 온도 등 합성변수들이 소재특성 및 전기화학적 특성에 미치는 영향을 조사하였다.

• Child Health Nursing Research
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• 제2권2호
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• pp.5-18
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• 1996

The purposes of this study were to measure the degree of perceived uncertainty and to identify the rearing attitudes of mothers with chronically ill children, and to examine the relationship between the perceived uncertainty and the rearing attitude of these mothers. The subjects of this study consisted of 133 mothers with chronically ill children, registered at 2 university hospitals in Seoul. Data was collected from April 1 to May 31, 1996. The Parents' Perception of Uncertainty Scale(28-item 4 point scale) and the Maternal Behavior Research Instrument (49-item 5 point scale) were used. Data was analyzed by Cluster analysis, ANOVA MANOVA and t-test. Results of this study are summarized as follows : 1. Mothers perceived their uncertainty to be slightly high (Mn 2.48). The degree of perceived uncertainty by the four components slightly differed unpredictability(2.72), lack in clarity(2.58), vagueness (2.52) and lack of information(2.04) . The degree of perceived uncertainty of mothers with ill children revealed to be influenced significantly by the age of the ill children, duration of illness after the diagnosis, and the experience of hospitalization. 2. Among the rearing attitudes : moderatlely high affective(Mn 3.98) and resrictive(Mn 3.58) attitudes of mothers toward their ill children were identified. Mothers tend to give positive evaluations of their childrens' behaviors (Mn 3.38) and less rejection(Mn 2.81). 3. Mothers' rearing attitude were correlated with the degree of perceived uncertainty in illness ; mothers in the Low Perceived Uncertainty Group (Mn 1.99) revealed the highest affective (Mn 4.08), the lowest resrictive(Mn. 2.72) attitudes and tendency to give positive evaluations of their childrens' behaviors (Mn 3.54) compared to the High Perceived Uncertainty Group(Mn 3.26) and Moderate Perceived Uncertaity Group(Mn 2.57). 4. The degree of perceived uncertainty, the duration of illness after the diagnosis and the experience of hospitalization revealed to be significantly influential to the rearing attitude of mothers with chronically ill children. From the above results, it can be concluded that predicting and controlling mothers' uncertainty are necessary for improved, efficient nursing interventions and normal growth & development of the chronically ill children.

• 동력기계공학회지
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• 제17권6호
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• pp.122-129
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• 2013

The microstructure and deformation behavior in 22Cr-0.2N micro-duplex stainless steels with various Ni and Mn contents were compared using by OM, TEM, and XRD. The 22Cr-0.2N duplex stainless steel plates were fabricated and hot rolled, followed by annealing treatment at the temperature range of $1,000-1,100^{\circ}C$. All the samples showed the common strain hardening behaviour during the tensile test at a room temperature. The steels tested at the temperatures of $-30^{\circ}C$ or $-50^{\circ}C$ showed a distinct inflection point in the stress-strain curves, which should be resulted from the formation of strain-induced martensite(SIM) of austenite phase. This was confirmed by TEM observations. The onset strain of a inflection point in a stress-strain curve should be depended up the value of $M_d30$. With the decrease of the tensile test temperature, the inflection point appeared earlier, and the strength and fracture strain were higher. The tensile behaviour was discussed from the point of austenite stability of the micro-duplex stainless steels with the different Ni and Mn content.

• 열처리공학회지
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• 제11권4호
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• pp.274-282
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• 1998

The effect of Al addition on the fatigue properties of austenitic Fe-25Mn-Al-0.5C steels was studied. When Al was not added to the Fe-25Mn 0.5C steel, the strain induced ${\varepsilon}$ martensites, deformation twins and slip bands were formed during fatigue deformation. When 2wt% of Al was added to the steel, the deformation twins and slip bands were formed during fatigue deformation. When 5wt% of Al was added, only slip bands were formed. In low cycle fatigue test, the alloys containing 0wt% and 2wt%Al showed the cyclic hardening due to ${\varepsilon}$ martensites and deformation twins, resulting in shorter fatigue lives than the alloy containing 5wt%Al. In fatigue crack propagation test, the alloy without Al showed the highest crack propagation rate. The fracture surface of the alloy without Al was flat, whereas that of the alloy with 2% or 5%Al was rough. The ${\Delta}K_{th}$, values of the alloys with 0%, 2% and 5%Al were 16, 17.5, and $20.5MPam^{1/2}$, respectively.