• 대한금속재료학회지
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• 제47권9호
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• pp.558-566
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• 2009

The alloying effect of a small amount of nickel on low alloy steel for application to flue gas desulfurization(FGD) systems was studied. The structural characteristics of the rust layer were investigated by scanning electron microscopy(SEM). The electrochemical properties were examined by means of potentiostatic polarization test, potentiodynamic polarization test, and electrochemical impedance spectroscopy(EIS) in a modified green death solution of 16.9 vol.% $H_2SO_4$+0.35 vol.% HCl at $60^{\circ}C$ and an acid rain solution of $6.25{\times}10^{-5}M\;H_2SO_4+5.5{\times}10^{-3}M\;NaCl$ at room temperature. It was found that as the amount of nickel increased, the corrosion rate increased in the modified green death solution, which seemed to result from micro-galvanic corrosion between NiS and alloy matrix. In acid rain solution, the corrosion rate decreased as the amount of nickel increased due to the repulsive force of $NiFe_2O_4$ rust against $Cl^-$ ions by electronegativity.

• Advances in concrete construction
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• 제14권5호
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• pp.341-354
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• 2022

Treatment of solid waste building materials is a crucial method of disposal and an area of ongoing research. New standards for the treatment of solid waste building materials are necessary due to multisource features, huge quantities, and complicated compositions of solid waste. In this research, sustainable nanomaterial mixtures containing nano-paper waste (NPW) and nano-metakaolin (NMK) were used as a substitute for Portland cement. Portland cement was replaced with different ratios of NPW and NMK (0%, 4%, 8%, and 12% by weight of cement) while the cement-to-water ratio remained constant at 0.4 in all mortar mixtures. The fresh properties had a positive effect on them, and with the increase in the percentage of replacement, the fresh properties decreased. The results of compressive strength at 7 and 28 days and flexural strength at 28 days show that the nanomaterials improved the strength, but the results of NMK were better than those of NPW. The best replacement rate was 8%, followed by 4%, and finally 12% for both materials. The combination of NMK and NPW as a replacement (12% NMK + 12% NPW) showed less shrinkage than the others because of the high pozzolanic reactivity of the nanomaterials. The combination of NMK and NPW improved the microstructure by increasing the hydration volume and lowering the water in the cement matrix, as clearly observed in the C-S-H decomposition.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.174-177
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• 2003

We report four new phosphorescent iridium(III} complexes with 2,4-diphenyl-1,3-oxazole [$Ir(24dpo)_3$], 2,5-diphenyl-1,3-oxazole [$Ir(25dpo)_3$], 2-(3-thienyl) pyridine [$Ir(3thpyh)_3$] and [Ir(3thpy)2(acac)]. Three of them demonstrate good photophysical properties to be used as dopants to organic polymer matrix or to be used "as is" without a host matrix to fabricate OLEDs. Green and yellow light emission was observed for the photoluminescence: 569/525, 549/498 nm and 557,604/533 (solid state/$CH_2Cl_2$ solution) for $Ir(24dpo)_3$, $Ir(3thpyh)_3$ and $Ir(3thpyh)_2$acac respectively. Room temperature luminescent lifetimes are 2.5 and 1.8 ${\mu}s$ and quantum efficiencies 37 and 53%for $Ir(24dpo)_3$ and $Ir(3thpyh)_3$. The complexes are stable in air and sublimable at low pressure without considerable decomposition. Comparison of physicochemical properties of the reported iridium(III) cyclometalated compounds with that known from literature is carried out.

• 한국전자파학회논문지
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• 제15권5호
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• pp.499-508
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• 2004

마이크로스트립 구조체를 해석하는데 있어, 행렬 요소를 해석적으로 계산할 수 있는 효율적인 모멘트법이 제안된다. 본 논문의 모멘트법에서는 공간영역 그린함수로 Bessel 함수의 반 무한구간 정적분에 관한 공식에 근거하여 유도된 새로운 형태의 closed-form 그린함수를 사용한다. 본 논문의 모멘트법을 사용할 경우 기존의 모멘트법의 사용에 비해, 계산량 및 계산 속도와 같은 수치계산 효율 측면에서 약 4배 정도로 개선됨을 알 수 있었다. 본 논문이 제안하는 방법의 타당성을 확인하기 위하여 몇 가지 수치해석 결과를 제시한다.

• 한국통신학회논문지
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• 제29권6C호
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• pp.751-762
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• 2004

본 논문에서는 삼각 셀을 이용하여 2$^n$개의 서로 다른 극수를 갖는 새로운 GRM 계수의 생성 기법을 제안한다. 기존의 GRM 계수 생성방법으로는 주어진 RM제수를 변환행렬과 연산하는 Green 등의 방법과 기본 전달행렬들을 만복 적용하여 다른 극수들을 구하는 Besslich 등의 방법이 대표적이다. 본 논문에서 효율적인 GRM 계수의 생성을 위하여 삼각 셀을 정의하였고, 삼각 셀의 첫 행에 2n개의 주어진 RM계수를 나열한 후 고정된 수식에 의해 하위 열에 순차적 모듈로 합을 행하는 병렬형 방법이다. 제안한 연산 기법의 효율성을 예증하기 위해 기존의 기법들과 비교하였고, 비교결과 n개의 입력 변수에서 모든 극수의 GRM 계수들을 구하는데 같은 시스템 복잡도 (log 2$^n$) $T_{X}$에 대하여 Besslich 등의 기법은 2$^n$$^{-1}$／${\times}$(2$^n$-1)개의 2입력 Ex-OR가 필요한 반면에 본 논문에서 제안한 기법은 2${\times}$(n-1변수의 Ex-OR 개수) + 3$^n$$^{-1}$ 개의 2입력 Ex-OR만을 필요로 한다.다..

• Molecules and Cells
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• 제38권3호
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• pp.267-272
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• 2015

Nacre seashell is a natural osteoinductive biomaterial with strong effects on osteoprogenitors, osteoblasts, and osteoclasts during bone tissue formation and morphogenesis. Although nacre has shown, in one study, to induce bridging of new bone across large non-union bone defects in 8 individual human patients, there have been no succeeding human surgical studies to confirm this outstanding potency. But the molecular mechanisms associated with nacre osteoinduction and the influence on bone marrow-derived mesenchymal stem cells (BMSC's), skeletal stem cells or bone marrow stromal cells remain elusive. In this study we highlight the phenotypic and biochemical effects of Pinctada maxima nacre chips and the global nacre soluble protein matrix (SPM) on primary human bone marrow-derived stromal cells (hBMSCs) in vitro. In static co-culture with nacre chips, the hBMSCs secreted Alkaline phosphatase (ALP) at levels that exceeded bone morphogenetic protein (rhBMP-2) treatment. Concentrated preparation of SPM applied to Stro-1 selected hBMSC's led to rapid ALP secretions, at concentrations exceeding the untreated controls even in osteogenic conditions. Within 21 days the same population of Stro-1 selected hBMSCs proliferated and secreted collagens I-IV, indicating the premature onset of an osteoblast phenotype. The same SPM was found to promote unselected hBMSC differentiation with osteocalcin detected at 7 days, and proliferation increased at 7 days in a dose-dependent manner. In conclusion, nacre particles and nacre SPM induced the early stages of human bone cell differentiation, indicating that they may be promising soluble factors with osteoinductive capacity in primary human bone cell progenitors such as, hBMSC's.

• Advances in nano research
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• 제15권5호
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• pp.385-399
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• 2023

Hexagonal boron nitride (h-BN), commonly referred to as Boron Nitride Nanoribbons (BNNRs), is an electrical insulator characterized by high thermal stability and a wide bandgap semiconductor property. This study delves into the electronic properties of two BNNR configurations: Armchair BNNRs (ABNNRs) and Zigzag BNNRs (ZBNNRs). Utilizing the nearest-neighbour tight-binding approach and numerical methods, the electronic properties of BNNRs were simulated. A simplifying assumption, the Hamiltonian matrix is used to compute the electronic properties by considering the self-interaction energy of a unit cell and the interaction energy between the unit cells. The edge perturbation is applied to the selected atoms of ABNNRs and ZBNNRs to simulate the electronic properties changes. This simulation work is done by generating a custom script using numerical computational methods in MATLAB software. When benchmarked against a reference study, our results aligned closely in terms of band structure and bandgap energy for ABNNRs. However, variations were observed in the peak values of the continuous curves for the local density of states. This discrepancy can be attributed to the use of numerical methods in our study, in contrast to the semi-analytical approach adopted in the reference work.

• Nano
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• 제13권10호
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• pp.1850119.1-1850119.6
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• 2018

$Eu^{3+}/Tb^{3+}$ co-doped nanocomposite containing $CeO_2$ nanocrystals was successfully prepared by an in situ sol-gel polymerization approach. High-resolution transmission electron microscopy demonstrated the homogeneous precipitation of $CeO_2$ nanocrystals among the polymethylmethacrylate (PMMA) matrix. The thermal stability and UV-shielding capability of the obtained nanocomposite were improved with increase of $CeO_2$ content. The tuning of the emissive color from green and yellow to red can be easily achieved by varying the dopant species and concentration. These results suggested that the obtained nanocomposite could be potentially applicable in transparent solid-state luminescent devices.

• 자원환경지질
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• 제27권2호
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• pp.191-199
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• 1994

층상대지속에 있는 3차원 물체에 의한 지자기 지전류 (MT)응답을 계산하기 위하여 적분방정식을 이용한 수치모델링법을 개발하였다. 이 방법에서는 3차원 이상체를 몇 개의 세포로 분할하여 펄스기조함수로 근사할 수 있는 전류분포로 치환한다. 층상대지를 표현하는 전기 텐서그린함수를 쓰면 행렬방정식을 유도할 수 있으며 이를 각 세포의 벡터전류에 대하여 푼다. 결국 미지의 산란장은 산란전류에 관한 전기 및 자기 텐서그린함수를 적분함으로써 얻어진다. 지표면 근처에 3차원 전도성물체가 존재할 때 2차원의 TE모드 모델링으로는 깊은 곳에 가짜의 저 비저항을 가정해야 한다. 이는 TE모드 모델링에서는 경계면 전하의 영향을 고려할 수 없기 때문이다. 그러나 긴 3차원 직방체의 가운데를 가로지르는 단연은 2차원 TM모드 아르고리즘으로 정확히 모델화할 수 있으며, 이는 정식화과정에서 경계면 전하가 고려되어 있기 때문이다. 다중 주파수에 관한 수치계산 결과 겉보기 비저항과 위상은 상호보완적인 변수라는 것이 밝혀졌다. 따라서 이들 변수는 주파수영역 MT 해석시 함께 취급되는 것이 바람직하다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1995년도 봄 학술발표회 논문집
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• pp.17-27
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• 1995

For the post-buckling and elasto-plastic analysis of shell structures, the total Lagrangian formulation is presented based upon the degenerated shell element. Geometrically correct formulation is developed by updating the direction of normal vectors in the iteration process and evaluating the total Green-Lagrange stain corresponding U total displacements. In the calculation of the stiffness matrix, the element formulation takes into account the effect of finite rotation increments by retaining second order rotation terms in the incremental displacement field. The selective or reduced integration scheme using the heterosis element is applied in order to overcome both shear locking phenomena and the zero energy mode. The load/displacement incremental scheme is adopted for geometric non-linear F .E. analysis. Based on such methodology, the computer program is developed and numerical examples to demonstrate the accuracy and the effectiveness of the proposed shell element are presented and compared with references's results.