• 멤브레인
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• 제31권2호
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• pp.133-144
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• 2021

알칼리 수전해 시스템은 다양한 수소 생산 공정 중에서 가장 온실가스 발생량이 적은 그린 수소를 생산하는 방식 중 가장 오래된 기술이다. 알칼리 수전해 시스템은 알칼리 조건에서 사용되며, 고분자 전해질막 수전해와는 다르게 니켈, 코발트, 은 등의 안정한 전이금속을 전극촉매로 사용할 수 있다. 이 시스템은 가격이 저렴하고 대용량화가 용이하다는 장점을 가지고 있다. 이러한 장점으로 알칼리 수전해 시스템은 20세기 초부터 MW급 수소발생장치에 적용되어 왔으며 현재 20여 개의 제조업체에서 상용제품을 판매하고 있는 안정화된 기술이다. 본 논문에서는 알칼라인 수전해의 기본원리 및 사용되는 촉매, 전극, 격막 등에 대해 알아보고 그 중 핵심소재인 격막의 연구개발 동향에 대해 살펴보고자 한다.

• 동의생리병리학회지
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• 제33권3호
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• pp.163-168
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• 2019

In order to enhance the 8 principle pattern diagnosis rate comparing with diagnostic method by self-report questionnaire on cold/heat pattern in the clinical practice, a new diagnostic method using form-color-pulse-symptom (FCPS) system is proposed. FCPS system is composed of outputs of cold/heat pattern through the calculation process of contribution degree to the cold, heat pattern and qi, blood, yin, yang deficiency patterns, based on analysis of 16 mechanisms of disease calculated by diagnostic system of oriental medicine (DSOM) first. And second component is an output of differentiated 8 principle patterns in detail through binding and calculating process with digital informations of pulse, color, form, constitution obtained by computerized measurement system. Putting together above two processes consecutively, cold-heat complex or true/false cold/heat patterns and personalized characters of cold/heat patterns of each patient can be subdivided through a computation method of determining each pattern. In conclusion, 8 principle pattern identification can be performed more accurately using FCPS system than existent self report questionnaire method. These hypothetic proposal is needed to be proven by clinical trial for the future and then the accurate numbers used in each calculational function should be revised properly.

• Journal of the Korean Wood Science and Technology
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• 제47권4호
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• pp.509-518
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• 2019

This study analyzed the effect of organic solvent extractives on the classification of wood species via near-infrared spectroscopy (NIR). In our previous research, five species of Korean softwood were classified into three groups (i.e., Cryptomeria japonica (cedar)/Chamaecyparis obtuse (cypress), Pinus densiflora (red pine)/Pinus koraiensis (Korean pine), and Larix kaempferi (Larch)) using an NIR-based principal component analysis method. Similar tendencies of extractive distribution were observed among the three groups in that study. Therefore, in this study, we qualitatively analyzed extractives extracted by an organic solvent and analyzed the NIR spectra in terms of the extractives' chemical structure and band assignment to determine their effect in more detail. Cedar/cypress showed a similar NIR spectra patterns by removing the extractives at 1695, 1724, and 2291 nm. D-pinitol, which was detected in cedar, contributed to that wavelength. Red pine/Korean pine showed spectra changes at 1616, 1695, 1681, 1705, 1724, 1731, 1765, 1780, and 2300 nm. Diterpenoids and fatty acid, which have a carboxylic group and an aliphatic double bond, contributed to that wavelength. Larch showed a catechin peak in gas chromatography and mass spectroscopy analysis, but it exhibited very small NIR spectra changes. The aromatic bond in larch seemed to have low sensitivity because of the 1st overtone of the O-H bond of the sawdust cellulose. The three groups sorted via NIR spectroscopy in the previous research showed quite different compositions of extractives, in accordance with the NIR band assignment. Thus, organic solvent extractives are expected to affect the classification of wood species using NIR spectroscopy.

• 한국정보기술학회논문지
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• 제17권6호
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• pp.103-114
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• 2019

주파수변조연속파형(FMCW) 레이더 시스템을 사용하는 이동 객체탐지가 최근 각광을 받고 있다. 레이더 객체탐지는 탐지범위 내 존재하는 고정된 객체 및 클러터들로부터 반사되는 잡음신호로 인해 매우 도전적인 문제이다. 본 논문에서는 FCMW 레이다를 이용하여 잡음배경하 이동객체탐지를 위해 강인한 주성분분석법(RPCA)을 이용한다. 먼저 원 레이더 입력신호에 보상과 보정을 적용한다. 다음 경사하강법을 사용하는 RPCA가 저계수의 성질을 갖는 잡음배경 모델을 구하기 위해 사용된다. 본 논문에서는 RPCA 계산을 위해 소요계산량이 적은 새로운 업데이트 알고리즘을 제안한다. 마지막으로 이동객체는 자동 다중스케일에 기반한 피크 탐지법에 의해 정위한다. 모든 단계는 슬라이딩 윈도우 방법 기반하여 처리된다. 제안된 방법을 타 RPCA 기반의 방법들과 다양한 실험 시나리오 상에서 비교했을 때, 처리 속도와 정확도 척도에서 우수한 결과를 보였다.

• 센서학회지
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• 제30권6호
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• pp.436-440
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• 2021

The impact of the gate length (L_g) on the DC and high-frequency characteristics of indium-rich In_0.8Ga_0.2As channel high-electron mobility transistors (HEMTs) on a 3-inch InP substrate was inverstigated. HEMTs with a source-to-drain spacing (L_SD) of 0.8 ㎛ with different values of L_g ranging from 1 ㎛ to 19 nm were fabricated, and their DC and RF responses were measured and analyzed in detail. In addition, a T-shaped gate with a gate stem height as high as 200 nm was utilized to minimize the parasitic gate capacitance during device fabrication. The threshold voltage (V_T) roll-off behavior against L_g was observed clearly, and the maximum transconductance (g_{m_max}) improved as L_g scaled down to 19 nm. In particular, the device with an L_g of 19 nm with an L_SD of 0.8 mm exhibited an excellent combination of DC and RF characteristics, such as a g_{m_max} of 2.5 mS/㎛, On resistance (R_ON) of 261 Ω·㎛, current-gain cutoff frequency (f_T) of 738 GHz, and maximum oscillation frequency (f_max) of 492 GHz. The results indicate that the reduction of L_g to 19 nm improves the DC and RF characteristics of InGaAs HEMTs, and a possible increase in the parasitic capacitance component, associated with T-shap, remains negligible in the device architecture.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3310-3316
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• 2022

Owing to the rising concerns about the safety of nuclear power plants (NPP), it is essential to study the venturi scrubber in detail, which is a key component of the filtered containment venting system (FCVS). FCVS alleviates the pressurein containment byfiltering and venting out the contaminated air. Themain objective of this research was to perform a CFD investigation of different configurations of a circular, non-submerged, self-priming venturi scrubber to estimate and improve the performance in the removal of elemental iodine from the air. For benchmarking, a mass transfer model which is based on two-film theory was selected and validated by experimental data where an alkaline solution was considered as the scrubbing solution. This mass transfer model was modified and implemented on a unique formation of two self-priming venturi scrubbers in series. Euler-Euler method was used for two-phase modeling and the realizable K-ε model was used for capturing the turbulence. The obtained results showed a remarkable improvement in the removal of radioactive iodine from the air using a series combination of venturi scrubbers. The removal efficiency was improved at every single data point.

• 천문학회보
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• 제46권2호
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• pp.47.3-48
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• 2021

We studied the large scale dynamo process in a system forced by helical magnetic field. The dynamo process is basically nonlinear, but can be linearized with 𝛼&𝛽 coefficients and large scale magnetic field $\bar{B}$. This is very useful to the investigation of solar (stellar) dynamo. A coupled semi-analytic equations based on statistical mechanics are used to investigate the exact evolution of 𝛼&𝛽. This equation set needs only magnetic helicity ${\bar{H}}_M({\equiv}{\langle}{\bar{A}}{\cdot}{\bar{B}}{\rangle},\;{\bar{B}}={\nabla}{\times}{\bar{A}})$ and magnetic energy ${\bar{E}}_M({\equiv}{\langle}{\bar{B}}^2{\rangle}/2)$. They are fundamental physics quantities that can be obtained from the dynamo simulation or observation without any artificial modification or assumption. 𝛼 effect is thought to be related to magnetic field amplification. However, in reality the averaged 𝛼 effect decreases very quickly without a significant contribution to ${\bar{B}}$ field amplification. Conversely, 𝛽 effect contributing to the magnetic diffusion maintains a negative value, which plays a key role in the amplification with Laplacian ∇²(= - k²) for the large scale regime. In addition, negative magnetic diffusion accounts for the attenuation of plasma kinetic energy E_V(= 〈 U² 〉/2) (U: plasma velocity) when the system is saturated. The negative magnetic diffusion is from the interaction of advective term - U • ∇ B from magnetic induction equation and the helical velocity field. In more detail, when 'U' is divided into the poloidal component U_pol and toroidal one U_tor in the absence of reflection symmetry, they interact with - B • ∇ U and - U • ∇ B from ∇ × 〈 U × B 〉 leading to 𝛼 effect and (negative) 𝛽 effect, respectively. We discussed this process using the theoretical method and intuitive field structure model supported by the simulation result.

• 한국재료학회지
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• 제33권11호
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• pp.439-446
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• 2023

Changes in the microstructure and mechanical properties of as-roll-bonded AA6061/AA5052/AA1050 three-layered sheet with increasing annealing temperature were investigated in detail. The commercial AA6061, AA5052 and AA1050 sheets with 2 mm thickness were roll-bonded by multi-pass rolling at ambient temperature. The roll-bonded Al sheets were then annealed for 1 h at various temperatures from 200 to 400 ℃. The specimens annealed up to 250 ℃ showed a typical deformation structure where the grains are elongated in the rolling direction in all regions. However, after annealing at 300 ℃, while AA6061 and AA1050 regions still retained the deformation structure, but AA5052 region changed into complete recrystallization. For all the annealed materials, the fraction of high angle grain boundaries was lower than that of low angle grain boundaries. In addition, while the rolling texture of the {110}<112> and {123}<634> components strongly developed in the AA6061 and AA1050 regions, in the AA5052 region the recrystallization texture of the {100}<001> component developed. After annealing at 350 ℃ the recrystallization texture developed in all regions. The as-rolled material exhibited a relatively high tensile strength of 282 MPa and elongation of 18 %. However, the tensile strength decreased and the elongation increased gradually with the increase in annealing temperature. The changes in mechanical properties with increasing annealing temperature were compared with those of other three-layered Al sheets fabricated in previous studies.

• Earthquakes and Structures
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• 제26권5호
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• pp.383-400
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• 2024

For a conventionally repaired frame-supported-transfer-slab (FSTS) reinforced concrete (RC) structure, both the transfer slab and the beam-to-column and transfer slab-to-column joints remain vulnerable to secondary earthquakes. Aimed at improving the seismic performance of a damaged FSTS RC structure, an innovative retrofitting scheme is proposed, which adopts the sector lead rubber dampers (SLRDs) at joints after the damaged FSTS RC structure is repaired by conventional approaches. In this paper, a series of quasi-static cyclic tests was conducted on a large-scale retrofitted FSTS RC structure. The seismic performance was evaluated and the key test results, including deformation characteristics, damage pattern, hysteretic behaviour, bearing capacity and strains on key components, were reported in detail. The test results indicated that the SLRDs started to dissipate energy under the service level earthquake, and thus prevented damages on the beam-to-column and transfer slab-to-column joints during the secondary earthquakes and shifted the plastic hinges away from the beam ends. The retrofitting scheme of using SLRDs also achieved the seismic design concept of 'strong joint, weak component'. The FSTS RC structure retrofitted by the SLRDs could recover more than 85% bearing capacity of its undamaged counterpart. The hysteresis curves were featured by the inverse "S" shape, indicating good bearing capacity and hysteresis performance. The deformation capacity of the damaged FSTS RC structure retrofitted by the SLRDs met the corresponding codified requirements for the case of the maximum considered earthquake, as set out in the Chinese seismic design code. The stability of the FSTS RC structure retrofitted by the SLRDs, which was revealed by the developed stains of the RC frame and transfer slab, was improved compared with the undamaged FSTS RC structure.

• 방사성폐기물학회지
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• 제8권4호
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• pp.347-353
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• 2010

사용후핵연료를 파이로 건식처리하면 사용후핵연료 자체 내에 존재하는 세슘, 스트론튬, 초우라늄 계열 등이 중간저장 되어 영구처분 방사선원항에서 제외되므로 사용후핵연료집합체를 구성하는 구조재, 즉 금속폐기물의 방사선원항이 중요해지게 된다. 따라서 본 연구에서는 $17{\times}17$ KOFA 사용후핵연료 10 톤이 파이로 건식처리 되었을 경우를 가정하여 각 구조재 부품별로 방사선원항 특성을 분석하였다. 우선 구조재 부품별로 질량 및 부피를 상세히 계산하였다. 핵연료 상단 및 하단 고정체에서의 중성자스펙트럼이 노심과 다르므로 각 구조재 부품별로 핵반응단면적라이브러리를 KENO-VI/ORIGEN-S 모듈로 직접 생산하였으며, 이를 적용하여 ORIGEN-S 코드로 방사화 방사선원항을 평가하였다. 평가결과 원자로 방출후 10 년 시점에서의 방사능세기, 붕괴열, 위해지수 값은 각각 $1.40{\times}10^{15}$ Bequerels, 236 Watts, $4.34{\times}10^9m^3$-water 로 나타났으며, 이는 사용후핵연료 자체 값의 0.7 %, 1.1 %, 0.1 %에 해당하는 값이다. 방사능세기, 붕괴열, 위해지수 모든 측면에서는 금속폐기물 전체물량의 1 %만을 차지하는 인코넬 718 그리드판이 가장 중요한 것으로 평가되었으며, 특히 이를 따로 분리하여 관리하면 금속폐기물 전체 방사능세기를 20~45 % 정도, 위해지수를 30~45 % 정도 감소시킬 수 있는 것으로 나타났다. 전체적으로 볼 때, 금속폐기물의 방사능세기 및 위해지수는 처분시스템 설계 시 중요한 인자로 고려되어야 하나, 붕괴열은 그 열량이 작아 중요하지 않은 것으로 나타났다.