• Journal of the Optical Society of Korea
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• 제12권2호
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• pp.88-92
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• 2008

This paper discusses a photon-counting linear discriminant analysis (LDA) with computational integral imaging (II). The computational II method reconstructs three-dimensional (3D) objects on the reconstruction planes located at arbitrary depth-levels. A maximum likelihood estimation (MLE) can be used to estimate the Poisson parameters of photon counts in the reconstruction space. The photon-counting LDA combined with the computational II method is developed in order to classify partially occluded objects with photon-limited images. Unknown targets are classified with the estimated Poisson parameters while reconstructed irradiance images are trained. It is shown that a low number of photons are sufficient to classify occluded objects with the proposed method.

• 한국세라믹학회지
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• 제53권4호
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• pp.393-399
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• 2016

We have successfully fabricated 3D (3-dimensional) nanostructures of $TiO_2$ coated with a $g-C_3N_4$ layer via hydrothermal and sintering methods to enhance photoelectrochemical (PEC) performance. Due to the coupling of $TiO_2$ and $g-C_3N_4$, the nanostructures exhibited good performance as the higher conduction band of $g-C_3N_4$, which can be combined with $TiO_2$. To fabricate 3D nanostructures of $g-C_3N_4/TiO_2$, $TiO_2$ was first grown as a double layer structure on FTO (Fluorine-doped tin oxide) substrate at $150^{\circ}C$ for 3 h. After this, the $g-C_3N_4$ layer was coated on the $TiO_2$ film at $520^{\circ}C$ for 4 h. As-prepared samples were varied according to loading of melamine powder, with values of loading of 0.25 g, 0.5 g, 0.75 g, and 1 g. From SEM and TEM analysis, it was possible to clearly observe the 3D sample morphologies. From the PEC measurement, 0.5 g of $g-C_3N_4/TiO_2$ film was found to exhibit the highest current density of $0.12mA/cm^2$, along with a long-term stability of 5 h. Compared to the pristine $TiO_2$, and to the 0.25 g, 0.75 g, and 1 g $g-C_3N_4/TiO_2$ films, the 0.5 g of $g-C_3N_4/TiO_2$ sample was coated with a thin $g-C_3N_4$ layer that caused separation of the electrons and the holes; this led to a decreasing recombination. This unique structure can be used in photoelectrochemical applications.

• Geomechanics and Engineering
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• 제21권2호
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• pp.201-206
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• 2020

A stress-induced brittle failure in deep tunneling generates spalling and slabbing, eventually causing a v-shaped notch formation. An empirical relationship for the depth of the notch to the maximum tangential stress assuming an equivalent circular cross-section was proposed (Martin et al. 1999). While this empirical approach has been well recognized in the industry and used as a design guideline in many projects, its applicability to a non-circular opening is worth revisiting due to the use of equivalent circular profile. Moreover, even though the extent of the notch also contributes to notch failure, it has not been estimated to date. When the estimate of both the depth and the extent of notch are combined, a practical and economically justifiable support design can be achieved. In this study, a new methodology to assess the depth as well as the extent of notch failure is developed. Field data and numerical simulations using the Cohesion Weakening Frictional Strengthening (CWFS) model were collected and correlated with the three most commonly accepted failure criteria (σ₁/σ₃, D_is=σ_max/σ_c, σ_dev/σ_cm). For the numerical analyses, the D-shaped tunnel was used since most civil tunnels are built to this profile. Inferential statistical analysis is applied to predict the failure range with a 95% confidence level. Considering its accuracy and simplicity, the new correlation can be used as an enhanced version of failure assessment.

• 한국터널지하공간학회 논문집
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• 제19권2호
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• pp.195-212
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• 2017

운영 중 해저 터널의 안정성 평가에 응력, 수압 그리고 라이닝 및 주변지반의 강성 열화 등과 같은 다양한 계측 정보를 사용해서 역해석하면, 효율적인 오차율 이내의 결과를 획득할 수 있다. 선행 연구에서 검증된 차분진화 알고리즘 기반의 역해석 수행 시 FLAC3D 등 범용 지반해석 프로그램을 사용했지만, 상대적으로 해석시간이 오래 걸리고, 제어가 어려운 단점이 있다. 이러한 이유로, 본 연구에서는 상대적으로 해석시간이 짧게 소요되는 beam-spring 모델 기반의 FEM solver를 도입하였다. 원형 터널 단면의 구조해석이 가능한 beam-spring 프로그램을 Python 언어로 개발하여, 기구축된 차분진화 알고리즘과 결합하였다. 계측 데이터로부터 실시간에 가깝게 운영 중 터널의 안정성 평가가 가능할 것으로 판단된다.

• Geomechanics and Engineering
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• 제23권2호
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• pp.93-102
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• 2020

The excavation broken zones (EBZ) of gateways is a significant factor in determining the stability of man-made opening. The EBZ of 55 gateways with variety geological conditions were measured using Ground Penetrating Radar (GPR). The results found that the greatly depth of EBZ, the smallest is 1.5 m and the deepest is 3.5 m. Experimental investigations were carried out in the laboratory and in the coal mine fields for applying the combined arch support theory to large EBZ. The studies found that resin bolts with high tensile strength and good bond force could provide high pretension force with bolt extensible anchorage method in the field. Furthermore, the recently invented torque amplifier could greatly improve the bolt pretension force in poor lithology. The FLAC3D numerical simulation found that the main diffusion sphere of pretension force was only in the free segment zone of the surrounding rock. Further analysis found that the initial load-bearing zone thickness of the combined arch structure in large EBZ could be expressed by the free segment length of bolt. The using of high mechanical property bolts and steel with high pretension force will clearly putting forward the bolt length selection rule based on the combined arch support theory.

• 대한기계학회논문집B
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• 제39권11호
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• pp.871-884
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• 2015

유체이송 기술은 마이크로 유체시스템 개발에서 핵심문제로 인식되고 있다. 최근 명(2014)은 외부동력을 사용하지 않고 액적을 이동시킬 수 있는 새로운 개념을 제안하고, 초기에 반원통형 형상을 가지는 가상의 2차원 액적에 대한 수치해석을 통해 이 개념이 성립함을 보였다. 또한 명과 권(2015)은 친수성/소수성 표면위에서 초기 3차원 반구 형상의 실제 물 액적이송의 메커니즘을 시간에 따른 액적형상과 액적 내부의 운동에너지, 중력에너지, 표면자유에너지 및 압력에너지의 수치해석 결과를 통해 규명하였다. 본 연구는 새로운 개념을 확립시키기 위해 초기 구형액적에 대한 3차원 수치해석을 수행하고, 액적이송의 메커니즘을 모세관력 힘의 불균형 관점에서 액적 형상과 다양한 에너지의 수치해석 결과를 통해 규명하였다.

• BMB Reports
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• 제33권3호
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• pp.256-262
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• 2000

In this study the disassembly process of chlorophyII (ChI)protein complexes of a stay-green mutant (ore10 of Arabidopsis thaliana) was investigated during the dark incubation of detached leaves. During this dark-induced senescence (DIS), the Chi loss was delayed in the mutant, while the photochemical efficiency of photosystem II (PSII) or Fv/Fm was accelerated when compared with the wild type (WT) leaves. This indicates that the decrease in Fv/Fm is a separate process and not causally-linked to the degradation of Chi during DIS of Arabidopsis leaves. In the native green gel electrophoresis of the Chi-protein complexes, which was combined with an additional twodimensional SDS-PAGE analysis, the delayed senescence of this mutant was characterized by the appearance of an aggregate at 1 d or 2 d, as well as very stable light harvesting complex II (LHCII) trimers until 5 d after the start of DIS. The polypeptide composition of the aggregates varied during the whole DIS at 5 d. Dl protein appeared to be missing in the aggregates. This result supports the idea of a faster depletion of functional PSH in the mutants compared with WT, as suggested by the earlier reduction of Fv/Fm and the stable Chl a/b ratio in the mutants. At 5 d, the WT leaves also often showed aggregates, but the polypeptide composition was different from those of ore10. The results presented suggest that the formation of aggregates, or stable LHCII trimers in the stay-green mutants, is a way to structurally protect Chi-protein complexes from serious proteolytic degradation. Detailed disassembly processes of Chi-protein complexes in WT and ore10 mutants are discussed.

• 한국주조공학회지
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• 제26권1호
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• pp.17-26
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• 2006

The substitution of cooling method from water quenching to air cooling after solution heat treatment was aimed for the development of a convenient and economical heat treatment process of duplex stainless steels without deterioration of mechanical and corrosion resistant properties for the industry. In order to achieve this goal, the mechanical properties and corrosion properties of a ASTM A890-4A duplex stainless steel were systematically investigated as functions of casting condition and cooling method after solution heat treatment. A 3-stepped sand mold and a permanent Y-block mold were used to check the effects of solidification structure and cooling rate after solution heat treatment. The microstructural characteristics such as the ferrite/austenite phase ratio and the precipitation behavior of ${\sigma}$ phase and carbides were investigated by combined analysis of OM and SEM-EDX with an aid of TTT diagram. Hardness and tension test were performed to evaluate the mechanical properties. Impact property at $-40^{\circ}C$ and corrosion resistance were also examined to check the possibility of the industrial application of this basic study. Throughout this investigation, air-cooling method was proved to effectively substitute for water-quenching process after the solution heat treatment, when the duplex stainless steel was sand mold cast with a thickness below 15 mm or permanent mold cast with a thickness below 20 mm.

• 컴퓨터교육학회논문지
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• 제22권5호
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• pp.27-37
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• 2019

본 연구는 고등학생 대상 온라인 시뮬레이션 기반 HW설계 학습에서 학습자들의 성찰수준을 분석하기 위해, 5차시 HW설계 학습을 실시하고, 차시별 5개 성찰내용에 따른 성찰수준을 분석하였다. 또한 HW설계 학습의 만족도와 필요성을 조사하였다. 차시별 성찰수준 차이 분석 결과, 3차시 D-Flip Flop 학습의 성찰 수준이 1.23점(2점 만점)으로 가장 높았다. 성찰내용 간의 상관관계를 분석한 결과, 학습내용과 과제 해결 방법에서 높은 정적 상관관계(r=.781, p<.01)를, 과제 해결 방법과 다른 해결 방법에서 부적 상관관계(r=-.615, p<.05)를 나타냈다. HW설계 학습 만족도 조사 결과는 4.2점(5점 만점)을 나타냈으며, 대부분의 학생들이 고등학생 대상 HW설계 학습이 필요하고, 현재의 학습내용은 다소 어렵다는 의견이 많았다. 이를 통해 향후 HW설계 학습은 기초-심화로 구성된 콘텐츠와 온 오프라인이 병행된 교육과정 구성이 필요함을 알 수 있었다.

• 한국산업융합학회 논문집
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• 제19권3호
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• pp.133-143
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• 2016

The objective in here is to find the density, stiffness, and strength of truss-wall rectangular (TWR) model which is combined with lattice truss (MLT) inside space. The TWR unit-cell model is defined as a unit cell originated from a solid-wall rectangular (SWR) model and it has an empty space inside. Thus, the empty space inside of the TWR is filled with lattice truss model defined as TWR-MLT. The ideal solutions derived of TWR-MLT are based on TWR with MLT model and it has developed by Gibson-Ashby's theory. To validate the ideal solutions of the TWR-MLT, ABAQUS software is applied to predict the density, strength, and stiffness, and then each of them are compared with the Gibson-Ashby's ideal solution as a log-log scale. Applied material property is stainless steel 304 because of cost effectiveness and easy to get around. For the analysis, SWR and TWR-MLT models are 1mm, 2mm, and 3mm truss diameter separately within a fixed 20mm opening width. In conclusion, the relative Young's modulus and relative yield strength of the TWR-MLT unit model is reasonably matched to the ideal expectations of the Gibson-Ashby's theory. In nearby future, TWR-MLT model can be verified by advanced technologies such as 3D printing skills.t.