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Linear and non-linear analyses on the onset of miscible viscous fingering in a porous medium
류원선,김민찬 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.7
The onset of miscible viscous fingering in porous media was analyzed theoretically. The linear stability equations were derived in the self-similar domain, and solved through the modal and non-modal analyses. In the nonmodal analysis, adjoint equations were derived using the Lagrangian multiplier technique. Through the non-modal analysis, we show that initially the system is unconditionally stable even in the unfavorable viscosity distribution, and there exists the most unstable initial disturbance. To relate the theoretical predictions with the experimental work, nonlinear direct numerical simulations were also conducted. The present stability condition explains the system more reasonably than the previous results based on the conventional quasi-steady state approximation.
섭취를 통한 급성중독으로 단일기관 응급실을방문한 소아환자의 나이대별 특성
류원선,최재연,조진성,임용수,현성열,양혁준 대한소아응급의학회 2018 대한소아응급의학회지 Vol.5 No.1
Purpose: To investigate the age group characteristics of children who visited the emergency department with acute poisoning by ingestion. Methods: We reviewed children under 19 years who visited the emergency department for acute poisoning by ingestion from 2012 to 2017. The children were divided into 3 age groups; infants (0-1 years), preschoolers (2-5 years), and schoolers (6-18 years). Clinical characteristics, intentional ingestion, involved substances (drugs, household products, artificial substances, and pesticides), decontamination and antidote therapy, and outcomes of the 3 age groups were compared. We also performed multivariable logistic regression analysis to identify factors associated with hospitalization. Results: A total of 622 children with acute poisoning by ingestion were analyzed. Their annual proportions to overall pediatric emergency patients ranged from 0.3% to 0.4%. Age distribution showed bimodal peaks at 0-2 years and 15-17 years. The infants showed lower frequency of girls, intentional ingestion, ingestion of drugs, performance of decontamination and antidote therapy, and hospitalization than 2 older groups (P < 0.001). Most decontamination, antidote therapy, and hospitalization occurred in the schoolers (P < 0.001). The most frequently reported substances were household cleaning substances in the infants (18.2%), antihistamines in the preschoolers (15.8%), and analgesics in the schoolers (37.5%). The factors associated with hospitalization were intentional ingestion (adjusted odds ratio [aOR], 7.08; 95% confidence interval [CI], 2.85-17.61; P = 0.001) and schoolers (aOR, 2.33; 95% CI, 1.10-7.53; P = 0.031; compared with infants). Only 1 in-hospital mortality was found in a boy aged 2 years who ingested methomyl. Conclusion: Infants may experience non-intentional ingestion, ingestion of non-pharmacologic substances (especially household cleaning substances), discharge without decontamination and antidote therapy more frequently than older children. Thus, we need age group-specific, preventive and therapeutic plans for children with acute poisoning.
등가회로모델을 이용한 역전기투석 스택전지의 성능에 대한 수치모사
류원선,유진수 한국막학회 2017 한국막학회 총회 및 학술발표회 Vol.2017 No.11
역전기투석전지는 염수-기수의 농도차이를 원동력으로 이온교환막의 선택성에 의해 양이온과 음이온을 서로 반대방향으로 이동시켜 전력을 생산한다. 이상적인 이온교환막의 경우 35 g/L과 0.5 g/L 농도의 염수와 기수를 흘려 보냈을 때, 약 0.1 V의 전압 출력을 가진다. 본 연구에서는 역전기투석 스택전지의 출력특성에 영향을 주는 인자로서 막저항, 염수와 기수의 전기전도도, 막 이동수, 막 면적, 유로 두께 및 메쉬의 개방면적비, 스택수 등을 고려하여 수치모사를 수행하였다. 스택전지 내 유로에서 발생하는 누설전류 및 내부저항을 고려한 등 가회로모델을 수립하였고, 상용 이온교환막으로 제작된 스택전지 실험결과로부터 개방전압, 단락전류밀도, 최대전력밀도와 같은 중요 전지특성에 대하여 수치 모사의 정합성을 확인하였다.
Effect of vertically varying permeability on the onset of convection in a porous medium
류원선,김민찬 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.6
Considering the vertically varying permeability of a porous medium, we conducted theoretical and numerical analyses on the onset of buoyancy-driven instability in an initially quiescent, fluid-saturated, horizontal porous layer. Darcy’s law was employed to explain the fluid flow through a porous medium and linear and nonlinear analyses are conducted. In the semi-infinite domain, the growth of disturbance and the onset of convection were analyzed with and without the quasi-steady state approximation. The present analysis of initial growth rate shows that the system is initially unconditionally stable regardless of a vertical heterogeneity parameter. The onset conditions of buoyancydriven instabilities were investigated as a function of the Darcy-Rayleigh number and the heterogeneity parameter. To find the effect of a vertical heterogeneity on the flow after the onset of convection, nonlinear numerical simulations also were conducted using the result of the linear analysis as a starting point. Nonlinear numerical simulations show that the finger-like instability motion is not readily observable at a critical time and it becomes visible approximately when a mass transfer rate substantially increases.
정혜원,류원선,Chul-Woo Park,Junghoon Kim,Hyungwoo Lee 한국분자세포생물학회 2023 Molecules and cells Vol.46 No.7
Age-related macular degeneration (AMD) is one of the leading causes of blindness in elderly individuals. However, the currently used intravitreal injections of anti-vascular endothelial growth factor are invasive, and repetitive injections are also accompanied by a risk of intraocular infection. The pathogenic mechanism of AMD is still not completely understood, but a multifactorial mechanism that combines genetic predisposition and environmental factors, including cellular senescence, has been suggested. Cellular senescence refers to the accumulation of cells that stop dividing due to the presence of free radicals and DNA damage. Characteristics of senescent cells include nuclear hypertrophy, increased levels of cell cycle inhibitors such as p16 and p21, and resistance to apoptosis. Senolytic drugs remove senescent cells by targeting the main characteristics of these cells. One of the senolytic drugs, ABT-263, which inhibits the antiapoptotic functions of Bcl-2 and Bcl-xL, may be a new treatment for AMD patients because it targets senescent retinal pigment epithelium (RPE) cells. We proved that it selectively kills doxorubicin (Dox)-induced senescent ARPE-19 cells by activating apoptosis. By removing senescent cells, the expression of inflammatory cytokines was reduced, and the proliferation of the remaining cells was increased. When ABT-263 was orally administered to the mouse model of senescent RPE cells induced by Dox, we confirmed that senescent RPE cells were selectively removed and retinal degeneration was alleviated. Therefore, we suggest that ABT-263, which removes senescent RPE cells through its senolytic effect, has the potential to be the first orally administered senolytic drug for the treatment of AMD.