• 대한조선학회논문집
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• 제45권6호
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• pp.590-600
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• 2008

This paper concerns the development of a designer friendly hull form parameterization and its coupling with advanced global optimization algorithms. As optimization algorithms, we choose the Partial Swarm Optimization(PSO) recently introduced to solve global optimization problems. Most general-purpose optimization softwares used in industrial applications use gradient-based algorithms, mainly due to their convergence properties and computational efficiency when a relatively few number of variables are considered. However, local optimizers have difficulties with local minima and non-connected feasible regions. Because of the increase of computer power and of the development of efficient Global Optimization (GO) methods, in recent years nongradient-based algorithms have attracted much attention. Furthermore, GO methods provide several advantages over local approaches. In the paper, the derivative-based SQP and the GO approach PSO are compared with their relative performances in solving some typical ship design optimization problem focusing on their effectiveness and efficiency.

• 대한조선학회논문집
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• 제39권4호
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• pp.1-10
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• 2002

초기쇄파의 수치모사에는 지금까지 경계적분법이 주로 쓰여왔고, 이 방법은 과도한 계산시간의 문제를 제외하고는 어느 정도 성공적이라고 할 수 있다. 본 논문에서는 쇄파실험을 수치모사하기 위한 새로운 수치기법을 보였다. 이 수치기법은 고차 스펙트럴/경계요소법과 경계적분법을 순차적으로 사용하며, 계산시간을 현저히 줄여준다. 조파 및 파 에너지 집중과정은 고차 스펙트럴/경계요소법에 의해 효율적으로 수치모사되고, 파의 전복과정만이 경계적분법에 의해 계산된다. 계산예에서 높은 입자속도와 가속도 등 쇄파의 두드러진 특성이 보여졌다.

• KSBB Journal
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• 제26권2호
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• pp.119-125
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• 2011

In the synthesis of nanoparticles, much attention has been paid to regulating the particle size. There has been a possible evident that using the central cavity (core) of the protein ferritin has a greatly significant influence on it because the core can generate the nanometer-sized mineral particles of variable metal ions. In this report, recombinant human L-ferritins produced from Saccharomyces cerevisiae were purified and their molecular properties were characterized. The cDNA for human ferritin L chain was also expressed in another host such as Escherichia coli, and the properties of recombinant L-ferritins were compared. From isoelectric focusing experiment, the L-ferritin from the recombinant yeast showed no indication of N-glycosylation. Some post-translational modifications other than N-glycosylation were speculated in the L-ferritins from yeast. A difference was made in the L-ferritins in their iron uptake rates and the initial rate of the L-ferritin from yeast was slightly increased. The reconstitution yield and size distribution of the core minerals were analyzed in the L-ferritins by transmission electron microscopy. The L-ferritin from yeast with higher reconstitution yield (54.5%) showed slightly larger sizes (mean 6.92 nm) with narrower size distribution than the L-ferritin from E. coli. It is, in conclusion, speculated that L-ferritin from yeast is relatively superior to the other, in view of the size of nanoparticle and its relative homogeneity.

• Current Optics and Photonics
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• 제2권2호
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• pp.147-152
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• 2018

We propose a novel bi-focal metallic Fresnel zone plate (MFZP) with shallow depth-of-field (DOF) characteristics. We design the specific annular slit patterns, exploiting the phase-selection-rule method along with the particle swarm optimization algorithm, which we have recently proposed. We numerically investigate the novel characteristics of the bi-focal MFZP in comparison with those of another bi-focal MFZP having equivalent functionality but designed by the conventional multi-zone method. We verify that whilst both bi-focal MFZPs can produce dual focal spots at $15{\mu}m$ and $25{\mu}m$ away from the MFZP plane, the former exhibits characteristics superior to those of the latter from the viewpoint of axial resolution, including the axial side lobe suppression and axial DOF shallowness. We expect the proposed bi-focal MFZP can readily be fabricated with electron-beam evaporation and focused-ion-beam processes and further be exploited for various applications, such as laser micro-machining, optical trapping, biochemical sensing, confocal sensing, etc.

• 한국어학
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• 제72권
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• pp.257-282
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• 2016

The aim of this paper is to research phonological and morphological features in Korean Voices from Berlin. The Korean Voices from Berlin was recorded in 1917 at Berlin by 5 Korean prisoners engaged in World War I, some of them came from North Hamgyeong Province, the others came from Pyeongan Province, therefore these data show a North Korean regional dialect. The data are composed of three materials, counting numbers, reciting scriptures and singing folksongs. The results of this research are as follows. 1) The consonant system of Korean voices is similar to standard Korean. The 19 consonants are classified according to 5 manners of articulations and 5 points of articulations. 2) The liquid /l/ has three allophones, [ɾ] appeared in an onset position, [l] in a word medial coda position or preceded by [l], [ɹ] in a word final coda position. 3) The vowel system of Korean voices is similar to early 20th Korean's. It has 8 monophthongs, /a, ʌ, o, u, ɯ, i, e, ${\varepsilon}$/. 4) The 1 to 10 numbers in Korean voices are similar to Middle-Korean numerals. 5) The genitive particle '/ɯi/의' is pronounced [i], [ɯ], [${\varepsilon}$], especially [ɯ] is appeared in Sino Korean. 6) The /l/-deletion of conjugations are similar to Middle-Korean, /l/ deletion always occurred, if [+cor] consonants are followed.

• Bulletin of the Korean Chemical Society
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• 제22권4호
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• pp.337-348
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• 2001

This article gives an overview of a recently developed channel system, frit-inlet asymmetrical flow field-flow fractionation (FI-AFlFFF), which can be applied for the separation of nanoparticles, proteins, and water soluble polymers. A conventiona l asymmetrical flow FFF channel has been modified into a frit-inlet asymmetrical type by introducing a small inlet frit near the injection point and the system operation of the FI-AFlFFF channel can be made with a great convenience. Since sample components injected into the FI-AFlFFF channel are hydrodynamically relaxed, sample injection and separation processes proceed without interruption of the migration flow. Therefore in FI-AFlFFF, there is no requirement for a valve operation to switch the direction of the migration flow that is normally achieved during the focusing/relaxation process in a conventional asymmetrical channel. In this report, principles of the hydrodynamic relaxation in FI-AFlFFF channel are described with equations to predict the retention time and to calculate the complicated flow variations in the developed channel. The retention and resolving power of FI-AFlFFF system are demonstrated with standard nanospheres and protreins. An attempt to elucidate the capability of FI-AFlFFF system for the separation and size characterization of nanoparticles is made with a fumed silica particle sample. In FI-AFlFFF, field programming can be easily applied to improve separation speed and resolution for a highly retaining component (very large MW) by using flow circulation method. Programmed FI-AFlFFF separations are demonstrated with polystyrene sulfonate standards and pululans and the dynamic separation range of molecular weight is successfully expanded.

• 천문학회보
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• 제44권2호
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• pp.55.2-55.2
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• 2019

The firehose instability is driven by a pressure anisotropy in a magnetized plasma when the temperature along the magnetic field is higher than the perpendicular temperature. Such condition occurs commonly in astrophysical and space environments, for instance, when there are beams aligned with the background magnetic field. Recently, it was argued that, in weak quasi-perpendicular shocks in the high-β intracluster medium (ICM), shock-reflected electrons propagating upstream cause the temperature anisotropy. This electron temperature anisotropy can trigger the electron firehose instability (EFI), which excites oblique waves in the shock foot. Scattering of electrons by these waves enables multiple cycles of shock drift acceleration (SDA) in the preshock region, leading to the electron injection to diffusive shock acceleration (DSA). In the study, the kinetic properties of the EFI are examined by the linear stability analysis based on the kinetic Vlasov-Maxwell theory and then further investigated by 2D Particle-in-Cell (PIC) simulations, especially focusing on those in high-β (β~100) plasmas. We then discuss the basic properties of the firehose instability, and the implication of our work on electron acceleration in ICM shock.

• 공업화학
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• 제31권1호
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• pp.84-89
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• 2020

초미세먼지로 분류되는 PM_2.5 (particulate matter under 2.5 ㎛) 중에서도 특히 sub-micron 입자(0.1~1.0 ㎛)의 먼지는 브라운 운동(Brownian motion)으로 집진장치의 효율에 한계를 준다. 따라서 수산화나트륨으로 활성화된 알루미늄산나트륨(NaAlO₂)을 응집제(coagulant)로 선택하여 석탄을 사용하는 유동층 보일러에서 석탄의 회분에 포함된 칼륨(K)과 PM_2.5의 입도분포의 거동과 영향을 확인하고자 했다. 그리고 응집제를 석탄의 무게대비 1,200 : 1 비율로 석탄에 혼합 및 분사하면서 정상 운전하는 중에 보일러의 싸이클론에서의 미세먼지(FP)와 전기집진기에서의 미세먼지(EP)를 포집 및 고찰하였다. 포집한 미세먼지를 입도분석기를 이용하여 입도분포(%)를 분석한 결과 FP에서 평균 4.87%에서 0.51%로 변화를 보임으로써 89.53% 감소하였다. EP에서의 평균 3.46%에서 0.40%로 변화를 보임으로써 88.57% 감소하였다. 포집한 미세먼지를 XRP로 칼륨을 추적한 결과 칼륨의 변화율은 FP에서 평균 1.65%에서 1.87%로 13.33% 증가하고, EP에서 평균 1.65%에서 2.03%로 17.68% 증가하였다. TMS에 의해서 확인된 총 미세먼지 농도(mg/㎥)는 1차는 2.6 mg/㎥에서 1.7~1.9 mg/㎥로 26.9~34.6% 감소하였으며, 2차는 평균 2.9 mg/㎥에서 1.7~1.9 mg/㎥로 33.3~40.4%가 감소하였다. 따라서 본 연구의 응집제가 PM_2.5 초미세먼지 입자의 크기와 그로 인한 집진장치효율에 크게 영향을 미치는 것으로 확인하였다.

• 공업화학
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• 제35권2호
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• pp.67-78
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• 2024

흡광은 측정이 간편하고 해석의 직관성이 높다는 점에서 생화학 기반 분석법의 신호로서 강점을 가진다. 흡광을 가지는 물질 중에서 금 나노입자는 화학적 안정성, 생물학적 친화성, 가시광선 범위에서 야기되는 국소 표면 플라즈몬 공명(localized surface plasmon resonance, LSPR)에 의한 독특한 광학적 특성 등의 유용한 성질을 지니며, 특정 표적 물질에만 유효한 다른 발색물질과 비교해 항체나 압타머 등 다양한 검출 활성물질과 접합이 용이하여 확장성을 가진다. 특히, 기질의 산화로 발색을 야기하는 효소 기반 발색법에 비해 낮은 가격, 쉬운 입자 합성, 높은 환경안정성 등의 장점으로 인해 비색화 분석법의 신호물질로서 광범위하게 연구되고 있다. 본 총설에서는 이와 같은 금 나노입자를 신호물질로 활용하는 다양한 전략을 최근의 연구들을 중심으로 요약 정리하였으며, 입자의 형태에 광학 특성이 영향을 받는 금 나노입자의 특징에 착안하여 신호생성 시에 활용한 금 나노입자의 형태 제어 전략을 기준으로 문헌들을 분류하고 검토하였다. 이를 통해 이미 오랜 기간 활용되어온 금 나노입자가 현재에도 흡광 신호물질로서 여전히 활발하게 연구되고 있다는 사실을 고찰하고, 향후에도 광범위하고 지속적으로 개선될 여지를 가진다는 점을 확인하였다.

• 한국컴퓨터그래픽스학회논문지
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• 제14권3호
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• pp.19-30
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• 2008

유체 시뮬레이션은 영화나 게임에 등장하는 물, 연기, 불, 폭발, 모래 등과 관련된 애니메이션을 생성하기 위해 유체운동 방정식을 풀어 형상화하는 컴퓨터 그래픽스 기술이다. 본 리뷰 논문은 유체 시뮬레이션에 대한 최근의 연구 동향을 영화를 중심으로 분석한다. 이를 위해 먼저 컴퓨터 그래픽스 분야에서 유체 시뮬레이션을 하는 방법과 이와 관련된 효율적 속도, 사실적 형상화 등의 기술적 이슈들을 격자 방법과 입자방법으로 분류하여 설명한다. 다음으로 2008년 Sci-Tech 오스카상을 수상한 유체 시뮬레이션 연구자 및 개발자들의 업적을 중심으로 그들이 제작한 영화 속에 사용된 기술의 특징을 설명한다. 이 과정을 통해 향후 영상 콘텐츠 분야의 유체 시뮬레이션 연구개발의 발전방향을 짚어보면 유체와 변형체나 고체사이의 상호작용, 상변이에 의한 위상 변화 표현, 유체 기반 크리쳐 생성과 크리쳐와 유체 상호작용 표현 기술이 주목을 받을 것으로 예상한다.