• 한국재료학회지
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• 제21권9호
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• pp.515-519
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• 2011

The purpose of this study was to determine the optimal firing condition and composition for $Al_2TiO_5$ crystal, which is suitable for stable coloration in glazes at high temperatures, using $Cr_2O_3$ as chromophore for the synthesis of $Al_2TiO_5$ system pigments. $Al_2TiO_5$ has a high refractive index and good solubility of chromophore in the $Al_2TiO_5$ lattice, making this structure a good candidate for the development of new ceramic pigments. Pigments were synthesized by using $Al_2O_3$ and $TiO_2$ mainly. Various amounts of $Cr_2O_3$ such as 0.01, 0.02, 0.03, 0.04 and 0.05 mole were also added. Each compound was synthesized at $1300^{\circ}C$, $1400^{\circ}C$, and $1500^{\circ}C$ for 2 hours and cooled naturally. The crystal structure, solubility limit, and color of the synthesized pigments were analyzed by XRD, SEM, Raman spectroscopy, UV and UV-vis. The changes in color as the result of applying 6 wt% of the synthesized pigments to lime barium glaze were expressed as CIE-L*a*b* values. A $Cr_2O_3$ 0.03 mole doped $Al_2TiO_5$ brown pigment was successfully synthesize at $1400^{\circ}C$, and the values of CIE-L*a*b* parameters were L* = 44.62, a* = 3.10, and b* = 17.25. In the case of the pigment synthesized at $1500^{\circ}C$, the brown color was obtained at 0.01 mole and 0.02 mole $Cr_2O_3$, and the CIE-L*a*b* values were 55.34, 1.73, 28.64, and 49.39, 0.51, 21.33, respectively. At $1500^{\circ}C$, the maximum limit of solid solution was 0.03 mole $Cr_2O_3$. The glazed sample showed green color, and the values of the CIEL* a*b* parameters were L* = 45.69, a* = -0.98, and b* = 20.38.

• 한국지능시스템학회논문지
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• 제21권4호
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• pp.499-505
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• 2011

본 논문은 파라미터 투영 기법이 필요없는 비선형 계통에 대한 적응 퍼지 슬라이딩 모드 제어를 제안한다. 제어기의 구조를 약간 수정하여 추정된 입력 이득항이 영으로 되지 않도록 보장하고 온라인 동작중의 어떤 순간이라고 추정된 입력 이득항이 영이 되더라도 구현에 문제를 야기하지 않는다. 입력 이득 함수의 하한 추정치만이 필요한것을 제외하면 제안한 제어 기법은 바운딩 파라미터에 대한 정확한 값이 사전에 필요하지 않다. 리아프노프 합성기법을 기초로 전체 제어 시스템이 추종오차가 점근적으로 안정하고 제어기 내의 모든 신호가 유계임을 보장한다. 역진자 시스템의 적용하여 제안한 제어기의 유용성을 입증한다.

• 한국통신학회논문지
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• 제29권9A호
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• pp.1091-1100
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• 2004

본 논문은 최적 모듈 선택 아키텍쳐 합성을 위한 천력 감소 Force-directed 스케줄링을 제안한다. 제안한 전력 강소 스케줄링은 행위 수준 언어를 업력으로 스위칭 활동-(switching activity) 을 고려하여 기존의 FDS 스케쥴링을 저 전력으로 고려한 FDS_LP 앙고리듬을 수행한다. 제안한 FDSL LP 알고리듬은 스위칭 활동을 최소로 하는 동적 파워를 포스 개념에 적용하여 전력 감소를 수행한다. 모듈 선택에서는 전력, 면적, 지연의 매개 변수를 고려하여 최척 모율 성택 RT 라이브러리를 구축한다. 구축한 RT 라이브러리에서 최적 파라메터를 구하기 위해서 프렌치 앤드 바운드 방법을 사용한 최걱 요율 선택 방법을 제안한다. 비교 실험에서는 최적 모율 선택을 고려한 제안한 FDS LP 앙고리듬과 기존의 FDS 알고리듬간의 전력 차이를 비교하여 최대 23.9 % 까지 전력 감소를 얻을 수 있다.

• 천문학회보
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• 제36권2호
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• pp.141.1-141.1
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• 2011

New CCD BVR light curves of BD And are presented. Our light curves with nearly equal depths for both primary and secondary eclipses show well-defined photometric waves outside eclipse for all of BVR bandpasses. The orbital period is greatly revised as $0.^d92580519$ which is twice longer than that known previously. Sixteen timings from our observations and thirteen ones from the SuperWASP measurements were calculated. All available timings over 76 years, including ours, were analyzed to figure out the dynamical behavior of the system. It was found that the recent CCD O-C residuals varied in a cyclical way with a period of $9.^y18$ and a semi-amplitude of $0.^d0046$. The secondary period of $9.^y18$ is the most shortest one among those which have been ever found in the short period RS CVn binary stars. The periodic variation most likely arises from the light-travel time effect due to a low-mass ($m_3{\sim}0.88\;M_{\odot}$) tertiary companion moving in an orbit with an large eccentricity ($e_3$=0.70) and a low inclination ($i_3{\sim}28^{\circ}$). The Applegate mechanism could not operate properly in both components because the model parameters require too much large luminosity changes of ${\Delta}L/L_{p,s}$ > 10. The new light curves were synthesized using the 2003 version of Wilson-Divinney code. It was found useful to model two huge spots on the surface of the hotter star and a third-light in order to minimize the residuals from the observations. Astronomical basic parameters were deduced from our photometric solution.

• 한국전자파학회논문지
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• 제13권6호
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• pp.546-551
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• 2002

본 논문에서는, 구조를 간략히 한 3중 조절형의 DDFS 구동PLL 주파수 합성기를 이용하여 주파수 합성 조절법에 의한 광대역 무선통신시스템으로의 응용을 연구하였다. 제안된 DDFS 구동PLL주파수 합성기는 DDFS에서 위상누적기만을 이용하는 매우 단순화된 구조이므로, 기존 DDFS 구동PLL 주파수 합성기의 경우보다 스위칭 속도가 높으며, 전력소모를 개선시킨다. 그리고 이 제안된 3중 조절형 주파수 합성기는 3가지 주파수 조절 파라미터를 이용하여 넓은 대역의 주파수 범위의 동작이 가능하므로, 광대역 저전력 고속 특성을 갖는 응용에 적합하다. 주파수 조절 파라미터 할당 방법과 그의 결과를 제시하였으며, CSM, IMT-2000, Bluetooth 틴 PCS 시스템, 등 여러 주파수 대역에 응용하는 경우를 보였다.

• Bulletin of the Korean Chemical Society
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• 제29권4호
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• pp.805-810
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• 2008

Using metallic Ti powder as raw materials and 1,2-diaminocyclohexane (DACH) as the trial template, two novel reduced titanophosphate open-structures were hydrothermally isolated by varying the $H_3PO_4/H_2O$ ratio to adjust the pH value. TiPO-1 crystallizes in orthorhombic Pbca space group with cell parameters a = 21.956(3) $\AA$, b = 8.6268(11) $\AA$, c = 7.2883(9) $\AA$, V = 1380.5(3) $\AA^3$, Z = 4. TiPO-2 crystallizes in triclinic space group P$\bar{1}$ with parameters a = 5.1620(10) $\AA$, b = 8.815(2) $\AA$, c = 10.655(3) $\AA$, $\alpha$ = $99.45^{\circ}$, $\beta$ = $102.94^{\circ}$, $\gamma$ = $91.06^{\circ}$, V = 465.34 $\AA^3$. TiPO-1 is constructed by infinite -Ti-O-Ti-O- linkage that is capped by $PO_4$ groups to form a chain structure with protonated DACH molecules occupying the interchain spaces. TiPO-2 represents a rare 3-D reduced titanophosphate with 12-MR channels. The structure of TiPO-2 is a neutral framework with water molecules located in the channels.

• Tribology and Lubricants
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• 제31권6호
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• pp.258-263
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• 2015

Biodiesel is an environmentally-friendly fuel with low smoke emission because it contains about 10% oxygen. Biodiesel fuel prepared by transesterification of vegetable oil or animal fats is susceptible to auto-oxidation. The rate of auto-oxidation depends on the number of methylene double bonds contained within the fatty acid methyl or ethyl ester groups. Biodiesel may be easily oxidized under several conditions, i.e., upon exposure to sunlight, temperature, oxygen environment. Maintenance of the fuel quality of biodiesel requires the development of technologies to increase the resistance of biodiesel to oxidation. Treatment with antioxidants is a promising approach for extending the shelf-life or storage time of biodiesel. The chemical properties of various amine-based antioxidants were evaluated after synthesis of the antioxidants by condensation of phenylenediamine with alkylamines at room temperature. In general, the oxidative stability can be assessed based on various experimental parameters. Such parameters may include temperature, pressure, and the flow rate of air through the samples. The Rancimat method (EN14112) was selected because it is a rapid technique that requires very little sample and provides good precision for oxidative degradation analysis. Specifically, the EN 14112 technique provides enhanced efficiency for oxidative stability evaluation when a larger ester head group is utilized. Therefore, this technique was employed for evaluation of the oxidation stability of biodiesel by the Rancimat method (EN14112).

• 물과 미래
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• 제8권1호
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• pp.61-79
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• 1975

본연구는 1974년 건설부 수자원국의 연구사업중의 하나인 $\ulcorner$홍수량 추정을 위한 합성단위유량도유도의 연구$\Ircorner$의 일부로서 건설부에서 제공한 재정적 후원에 감사를 드린다.

• 대한금속재료학회지
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• 제50권9호
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• pp.677-684
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• 2012

A feasible way to fabricate in-situ Al/TiC composites was investigated. An elemental mixture of $Al-TiO_2-C$ pellet was directly added into an Al melt at $800-920^{\circ}C$ to form TiC by self-combustion reaction. The addition of CuO initiates the self-combustion reaction to form TiC in $1-2{\mu}m$ at the melt temperature above $850^{\circ}C$. Besides the CuO addition, a diluent element of excess Al plays a significant role in the TiC formation by forming a precursor phase, $Al_3Ti$. Processing parameters such as CuO content, the amount of excess Al and the melt temperature, have affected the combustion reaction and formation of TiC, and their influences on the microstructures of in-situ Al/TiC composites are examined.

• Journal of Microbiology and Biotechnology
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• 제2권1호
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• pp.35-40
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• 1992

The influence of the nature of plasmids on fermentation parameters such as cell growth, cell viability, plasmid stability, and product formation has been investigated using E. coli M5248 and its recombinant derivatives M5248 [pBR322], M5248[pAS1], and M5248[pNKM21]. At a low temperature ($30^\circ{C}$), the cell growth, cell viability, and protein synthesis of the recombinants were nearly identical to those of the host cell. However, at high temperature ($42^\circ{C}$), in which transcription from the P_L$ promoter is derepressed, the recombinant cells showed decreased stability along with lower growth rates and cell viability. The ratio of total protein to cell mass was in the order of E. coli M5248>M5248[pBR322]>M5248[pAS1]>M5248[pNKM21]. It was found that transcription from the $P_L$ promoter adversely affect the plasmid maintenance and host cell metabolism even in the absence of the cloned-gene expression. Furthermore, profiles of ${\beta}$ activity were shown to vary with recombinant strains. E coli M5248[pBR322] showed highest ${\beta}-lactamase$ activity at $30^\circ{C}$, while at $42^\circ{C}\;{\beta}-lactamase$ activity was significantly reduced irrespective of the strains. The effect of the plasmid properties on plasmid-encoded gene expression has been further examined based on the relationship between $\{beta}-lactamase$ activity and plasmid-harboring cell numbers.