• 대한지하수환경학회지
• /
• 제1권2호
• /
• pp.100-104
• /
• 1994

기질내에서의 원소의 확산현상은 흡착 및 비흡착성 방사성핵종의 지하매질내 이동을 지연시키는 특성때문에 처분장의 안전성평가에서 매우 중요한 현상으로 간주된다. 이 현상을 실제 안전성평가에 적용하기 위하여 확산현상이 인지되는 자연현상 중에서 자연방사성원소의 농도변화 및 붕괴사슬을 이용한 자연유사 연구가 많이 수행되고 있고 그 현상이 준정량적으로 확인된다. 기질내 원소의 확산현상은 액체상의 흐름에 수반되어 일어나거나 열적 영향에 의해 국부적으로 일어나기도 하는데 후자의 경우는 고준위 방사성페기물 처분과 관련된 안정성평가에 그 중요성을 갖는다. 예를 들어 내덕리 화강암이 후기에 관입한 페그마타이트와 접촉하는 곳에서는 페그마타이트의 열적 영향에 의해 K, Rb, Sr 및 Ba과 같은 알카리 또는 알카리토 원소들과 Li, V및 Nb원소들이 접촉면으로부터 수직으로 약 9 cm 정도의 거리에 이르기까지 부화 또는 결핍된 이동현상이 관찰된다. 그러나 운반모델 설정을 위한 화산시간의 규모, 기질내 흡착된 핵종과 확산된핵종의 구분 등에 관한 연구는 필요한 시료의 취득치 불가능하여 이를 수행하지 못한 경우가 많다 이러한 문제점에도 불구하고 국내 처분장의 안전성 평가시에는 처분매질에 대하여 기질내 확산현상을 어느 정도 고려할 수 있는지를 자연유사 연구를 통해 규명되어야 할 것이다.

• 전기화학회지
• /
• 제1권1호
• /
• pp.33-39
• /
• 1998

본 연구에서는 전자-선 증발법으로 제조된 비정질의 텅스텐 산화물 박막과 전해질 계면에서 진행되는 전기화학반응을 1 M $LiCLO_4/PC$유기 전해질 계면에서 비정질의 텅스텐 산화물 박막 내부로 삽입된 리튬의 양론 값과 박막 전위의 변화에 대하여 연구하였다. 특히 복소수 임피던스 스펙트럼으로부터 제안된 박막과 전해질 계면의 등가 회로는 리튬의 층간 반응 기구가 텅스텐 산화물 박막/유기 전해질 계면에서 리튬 이온의 전하 전달 현상, 텅스텐 산화물 박막에 리튬의 흡착현상 및 박막 내부로의 리튬의 흡수 및 확산 현상으로 구성되어 있다는 것을 알 수 있었다. 또한 CNLS fitting법에 의하여 시뮬레이션된 $R_{ct},\;C_{dl},\;D$, 및 $\sigma_{Li}$ 등의 열역학 및 속도론적 변수 값 등의 상관 관계로부터,비정질의 텅스텐 산화물 박막의 소. 발색 특성은 이들 변수값과 관련이 있었으며, 특히 $Li_y,WO_3$, 박막 내의 리튬의 몰비 y=0.167및 전극 전위 E=2.25 V(vs. Li)에서 전기 발색의 한계값을 갖는 것으로 조사되었다.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제7권
• /
• pp.69-78
• /
• 1999

Effects of a non-absorbable gas on the absorption process in a vertical tube absorber has been investigated numerically. The water vapor mixed with air is absorbed into LiBr/water solution film. The flow is assumed to be laminar and fully developed in both liquid and gas phases. The diffusion and energy equations were solved in both phases to give the temperature and concentrations, from which heat and mass fluxes were determined. The local absorption rate has been shown to decrease as the mass fraction of air in the water vapor increases. The vapor pressure of water at the liquid-vapor is interface reduced significantly since the non-absorbable gas accumulates near the interface. The effects of non-absorbable gases on absorption rate become larger as the mass flow rate of the vapor decreases. For a small amount of non-absorbable gases, the total absorption rate of water vapor increases as the mass flow rate of the vapor decreases. The total absorption rate increases as the mass flow rate of the vapor increases for large concentrations of non-absorbable gases at the inlet of an absorber.

• 대한전자공학회논문지SD
• /
• 제39권1호
• /
• pp.58-66
• /
• 2002

Tapered 방향성 가중 결합 음향파 도파로를 이용하여 음향광학형 파장가변 광 필터를 LiNbO₃와 Ti 이중 확산 공정 기술을 이용하여 제작하였다. 1551.1㎚ 파장의 TE, TM 입사 편광모드와 173.58㎒ 35㎽ RF구동 신호에 대해서 각각 -14.29㏈, -14.99㏈ 부 모드 억압과 61%, 86% 변환효율이 측정되었다. 파장변화율과 통과 대역폭은 8.6㎚/㎒ 1.8㎚로 측정되었으며, 스위칭 속도는 2.82㎲로 측정되었다. 2.5㎚ 채널 간격에 대해서 약 -l4㏈누화 레벨이 측정되었으며, 부 모드와 채널 간격이 누화에 매우 큰 영향을 미치고있음을 확인하였다.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제6권
• /
• pp.56-66
• /
• 1998

The absorption process of water vapor in a liquid film is an important process in LiBr-Water absorption system. The composition of the gas phase, in which a non-absorbable gas is combined with the absorbate, influences the transport characteristics. In the present work, the absorption processes of water vapor into aqueous solutions of lithium bromide in the presence of non-absorbable gas are investigated. The continuity, momentum, energy and diffusion equations for the solution film and gas are formulated in integral forms and solved numerically. It is found that the mass transfer resistance in gas phase increases with the concentration of non-absorbable gas. However the primary resistance to mass transfer is in the liquid phase. As the concentration of non-absorbable gas in the absorbate increases, the interfacial temperature and concentration of absorbate in solution decrease, which results in the reduction of absorption rate. The reduction of mass transfer rate is found to be significant for the addition of a small amount of non-absorbable gas to the pure vapor, especially at the outlet of tube where the non-absorbable gas accumulates. At higher non-absorbable gas concentration, the decrease of absorption rate seems to be linear to the concentration of non-absorbable gas.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제14권2호
• /
• pp.41-48
• /
• 2006

Absorption performance at the vertical interface between refrigerant vapor and liquid solution of $LiBr-H_{2}O$ solution was enhanced by the waves formed due to the interfacial shear stress. The present study investigated experimentally and analytically the improvements of absorption performance in a falling film by wavy film flow. The dynamic parameter was the film Reynolds numbers ranged from 50 to 150. The energy and diffusion equations were solved simultaneously to find the temperature and concentration profiles at the interface of liquid solution and refrigerant vapor. Absorption characteristics due to heat and mass transfer were analyzed for the falling film of the LiBr aqueous solution contacted by refrigerant vapor in the absorber. Absorption performance showed a peak value at the solution flow rate of $Re_{f}>100$. Absorption performance for the wavy film flow was found to be greater by approximately 10% than that for uniform film flow. Based on numerical and experimental results, the maximum absorption rate was obtained for the wavy flow caused by spring insert. The difference between the measured and the predicted results were ranged from 5.8 to 12%.

• Nuclear Engineering and Technology
• /
• 제53권11호
• /
• pp.3653-3664
• /
• 2021

In PWR three-dimensional transient coupling calculation software CORCA-K, the nodal Green's function method and diagonal implicit Runge Kutta method are used to solve the spatiotemporal neutron dynamic diffusion equation, and the single-phase closed channel model and one-dimensional cylindrical heat conduction transient model are used to calculate the coolant temperature and fuel temperature. The LMW, NEACRP and PWR MOX/UO₂ benchmarks and FangJiaShan (FJS) nuclear power plant (NPP) transient control rod move cases are used to verify the CORCA-K. The effects of burnup, fuel effective temperature and ejection rate on the control rod ejection process of PWR are analyzed. The conclusions are as follows: (1) core relative power and fuel Doppler temperature are in good agreement with the results of benchmark and ADPRES, and the deviation between with the reference results is within 3.0% in LMW and NEACRP benchmarks; 2) the variation trend of FJS NPP core transient parameters is consistent with the results of SMART and ADPRES. And the core relative power is in better agreement with the SMART when weighting coefficient is 0.7. Compared with SMART, the maximum deviation is -5.08% in the rod ejection condition and while -5.09% in the control rod complex movement condition.

• 멤브레인
• /
• 제33권1호
• /
• pp.13-22
• /
• 2023

리튬 금속 기반 전극의 높은 용량에도 불구하고, 제어가 어려운 덴드라이트 성장은 낮은 쿨롱 효율, 안전 문제를 야기해, 리튬금속 배터리의 상용화를 제한한다. 본 연구에서는 압전 복합체인 BaTiO₃/PVDF (BTO@PVDF) 기반 보호층을 리튬금속에 코팅, 덴드라이트에 의한 부피팽창으로 발생한 변형을 분극을 이용하여, 리튬 금속 전극의 안정성 및 성능을 향상하고자 한다. 이를 통해, 균일한 리튬이온의 증착이 가능해졌으며, BTO@PVDF 전극은 100 사이클 동안 약 98.1% 이상의 쿨롱 효율을 나타내었다. 또한, CV를 통해 향상된 리튬이온의 확산계수(D_Li+) 증가를 보였으며, 본 연구에서 제시된 전략은 리튬 금속 전극의 성능 향상에 새로운 길을 나타내준다.

• 한국분말재료학회지
• /
• 제31권1호
• /
• pp.23-29
• /
• 2024

This study investigates the effect of the microstructure of Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP), a solid electrolyte, on its ionic conductivity. Solid electrolytes, a key component in electrochemical energy storage devices such as batteries, differ from traditional liquid electrolytes by utilizing solid-state ionic conductors. LATP, characterized by its NASICON structure, facilitates rapid lithium-ion movement and exhibits relatively high ionic conductivity, chemical stability, and good electrochemical compatibility. In this study, the microstructure and ionic conductivity of LATP specimens sintered at 850, 900, and 950℃ for various sintering times are analyzed. The results indicate that the changes in the microstructure due to sintering temperature and time significantly affect ionic conductivity. Notably, the specimens sintered at 900℃ for 30 min exhibit high ionic conductivity. This study presents a method to optimize the ionic conductivity of LATP. Additionally, it underscores the need for a deeper understanding of the Li-ion diffusion mechanism and quantitative microstructure analysis.

• Journal of Korean Neurosurgical Society
• /
• 제63권2호
• /
• pp.248-260
• /
• 2020

Objective : To investigate the efficiency of diffusion tensor imaging (DTI) fiber-tracking based neuronavigation and assess its usefulness in the preoperative surgical planning, prognostic prediction, intraoperative course and outcome improvement. Methods : Seventeen patients with cerebral masses adjacent to corticospinal tract (CST) were given standard magnetic resonance imaging and DTI examination. By incorporation of DTI data, the relation between tumor and adjacent white matter tracts was reconstructed and assessed in the neuronavigation system. Distance from tumor border to CST was measured. Results : The sub-portion of CST in closest proximity to tumor was found displaced in all patients. The chief disruptive changes were classified as follows : complete interruption, partial interruption, or simple displacement. Partial interruption was evident in seven patients (41.2%) whose lesions were close to cortex. In the other 10 patients (58.8%), delineated CSTs were intact but distorted. No complete CST interruption was identified. Overall, the mean distance from resection border to CST was 6.12 mm (range, 0-21), as opposed to 8.18 mm (range, 2-21) with simple displacement and 2.33 mm (range, 0-5) with partial interruption. The clinical outcomes were analyzed in groups stratified by intervening distances (close, <5 mm; moderated, 5-10 mm; far, >10 mm). For the primary brain tumor patients, the proportion of completely resected tumors increased progressively from close to far grouping (42.9%, 50%, and 100%, respectively). Five patients out of seven (71.4%) experienced new neurologic deficits postoperatively in the close group. At meantime, motor deterioration was found in six cases in the close group. All patients in the far and moderate groups received excellent (modified Rankin Scale [mRS] score, 0-1) or good (mRS score, 2-3) rankings, but only 57.1% of patients in the close group earned good outcome scores. Conclusion : DTI fiber tracking based neuronavigation has merit in assessing the relation between lesions and adjacent white matter tracts, allowing prediction of patient outcomes based on lesion-CST distance. It has also proven beneficial in formulating surgical strategies.