• Bulletin of the Korean Chemical Society
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• 제12권2호
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• pp.170-177
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• 1991

A lattice mean field theory is developed to investigate the conformational properties of monolayer amphiphiles at the air-water interface. By generalizing Dill and Cantor's method and by extending Whittington's recurrence equation, we derive the supermatrix recurrence equation which is applied to calculation of various segment density profiles and order parameter, etc. In deriving the equation, we incorporated the chain stiffness effect and the chain connectivity which are distinguished features of linear chain molecule. Our result shows that, as the surface coverage $\sigma$ increases the chain ordering process with respect to vertical axis of the lattice system becomes dominant.

• Journal of Advanced Research in Ocean Engineering
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• 제1권3호
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• pp.157-167
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• 2015

In order to provide simple and accurate wave theory in design of offshore structure, an analytical approximation is introduced in this paper. The solution is limited to flat bottom having a constant water depth. Water is considered as inviscid, incompressible and irrotational. The solution satisfies the continuity equation, bottom boundary condition and non-linear kinematic free surface boundary condition exactly. Error for dynamic condition is quite small. The solution is suitable in description of breaking waves. The solution is presented with closed form and dispersion relation is also presented with closed form. In the last century, there have been two main approaches to the nonlinear problems. One of these is perturbation method. Stokes wave and Cnoidal wave are based on the method. The other is numerical method. Dean's stream function theory is based on the method. In this paper, power series method was considered. The power series method can be applied to certain nonlinear differential equations (initial value problems). The series coefficients are specified by a nonlinear recurrence inherited from the differential equation. Because the non-linear wave problem is a boundary value problem, the power series method cannot be applied to the problem in general. But finite number of coefficients is necessary to describe the wave profile, truncated power series is enough. Therefore the power series method can be applied to the problem. In this case, the series coefficients are specified by a set of equations instead of recurrence. By using the set of equations, the nonlinear wave problem has been solved in this paper.

• 전자공학회논문지
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• 제50권11호
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• pp.195-205
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• 2013

집중에 관한 뇌파 해석은 인간의 인지 이해에 기본적인 요소이다. 본 연구에서는 시각자극에 대한 뇌의 집중, 비집중 상태의 차이특성을 비선형 분석하였다. 적은 샘플 데이터와 시간에 따른 변화특성을 해석하기 위하여 반복 정량 분석 법을 사용하였으며, 자극에 동기된 유발 전위의 반복궤적, 색상 반복 궤적을 도식화하였으며, 비선형 특징 파라미터들의 평균특징과 시변 특성을 추출하였다. 집중-비집중 도식과 파라미터 쌍은 위상공간 변환의 차원과 시간 지연을 결정하기 위한 정보를 제공하였으며, 집중 시의 뇌가 비집중 시의 뇌보다 복잡하다는 특징을 보였으며, 자극에 동기된 유발전위는 평균적 의미에서 동일 반응을 보이나 국부적으로는 환경과 상태에 따라 변화하였다. 본 실험을 통하여 시각자극에 대한 집중과 비집중 시 뇌의 비선형 현상을 해석하기 위한 가능성을 확인하였다.

• Journal of Chest Surgery
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• 제55권3호
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• pp.214-224
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• 2022

Background: Studies of the prognostic role of circulating tumor cells (CTCs) in early-stage non-small cell lung cancer (NSCLC) are still limited. This study investigated the prognostic power of CTCs from the pulmonary vein (PV), peripheral blood (PB), and bone marrow (BM) for postoperative recurrence in patients who underwent curative resection for NSCLC. Methods: Forty patients who underwent curative resection for NSCLC were enrolled. Before resection, 10-mL samples were obtained of PB from the radial artery, blood from the PV of the lobe containing the tumor, and BM aspirates from the rib. A microfabricated filter was used for CTC enrichment, and immunofluorescence staining was used to identify CTCs. Results: The pathologic stage was stage I in 8 patients (20%), II in 15 (38%), III in 14 (35%), and IV in 3 (8%). The median number of PB-, PV-, and BM-CTCs was 4, 4, and 5, respectively. A time-dependent receiver operating characteristic curve analysis showed that PB-CTCs had excellent predictive value for recurrence-free survival (RFS), with the highest area under the curve at each time point (first, second, and third quartiles of RFS). In a multivariate Cox proportional hazard regression model, PB-CTCs were an independent risk factor for recurrence (hazard ratio, 10.580; 95% confidence interval, 1.637-68.388; p<0.013). Conclusion: The presence of ≥4 PB-CTCs was an independent poor prognostic factor for RFS, and PV-CTCs and PB-CTCs had a positive linear correlation in patients with recurrence.

• International Journal of Heart Failure
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• 제6권1호
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• pp.28-33
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• 2024

Background and Objectives: Takotsubo syndrome (TTS) is a form of reversible cardiomyopathy often preceded by mental or physical stressors and predominantly affects elderly women. Several cardiac and inflammatory biomarkers are involved in the pathogenesis of the disease. We aimed to investigate the correlation of C-reactive protein (CRP) level with left ventricular ejection fraction (LVEF) and clinical outcomes in patients with TTS. Methods: The study included patients with discharge-diagnosis of Takotsubo through 2017-2022 from the cardiology department. Demographic, laboratory, echocardiographic, and clinical outcomes were retrospectively obtained. We investigated the relation between CRP and LVEF, length of stay (LOS), in-hospital complications, and recurrence. Results: A total of 86 patients (93% female, mean age 68.8±12.3 years) were included in the study. The median CRP level was 17.4 (interquartile range [IQR], 6.1-40.1) mg/L, and the mean LVEF was 41.5%, (IQR, 38-50%). Complications occurred in 24 (27.9%) of the patients, and the median LOS was 3 (IQR, 3-5) days. The level of CRP was associated with lower LVEF (r=-0.39, p<0.001), longer hospital stay (r=0.25, p=0.021), and recurrence. There was no correlation between CRP and in-hospital complications. In multivariate logistic regression, poor LVEF was associated with TTS recurrence (odds ratio, 1.22; 95% confidence interval, 1.08-1.37; p=0.001). Using linear regression, only CRP was correlated with longer LOS and lower LVEF (p<0.001). Conclusions: Among patients hospitalized with TTS, CRP level was associated with poor LVEF and prolonged hospital stay but not with in-hospital complications. Poor LVEF was also associated with TTS recurrence.

• 호남수학학술지
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• 제38권1호
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• pp.71-84
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• 2016

The aim of this work is to compute the volume of the graph polytope associated with various type of finite simple graphs composed of paths and stars. Recurrence relations are obtained using the recursive volume formula (RVF) which was introduced in Lee and Ju ([3]). We also discussed the relationship between the volume of the graph polytopes and the number of linear extensions of the associated posets for given bipartite graphs.

• Journal of applied mathematics & informatics
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• 제26권3_4호
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• pp.689-706
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• 2008

In this paper, a fifth order numerical method is presented for solving singularly perturbed two point boundary value problems with a boundary layer at one end point. The two point boundary value problem is transformed into general first order ordinary differential equation system. A discrete approximation of a fifth order compact difference scheme is presented for the first order system. An asymptotically equivalent first order equation of the original singularly perturbed two point boundary value problem is obtained from the theory of singular perturbations. It is used in the fifth order compact difference scheme to get a two term recurrence relation and is solved. Several linear and non-linear singular perturbation problems have been solved and the numerical results are presented to support the theory. It is observed that the present method approximates the exact solution very well.

• International Journal of Reliability and Applications
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• 제7권2호
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• pp.187-201
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• 2006

In this paper, we derive recurrence relations for the single and product moments of progressively Type-II right censored order statistics from half logistic distribution. Next, we derive the maximum likelihood estimators (MLEs) of the location and scale parameters of the half logistic distribution. In addition, we use the setup proposed by Balakrishnan and Aggarwala (2000) to compute the approximate best linear unbiased estimates (ABLUEs) of the location and scale parameters. Finally, we point out a simulation study to compare between the efficiency of the techniques considered for the estimation.

• International Journal of Arrhythmia
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• 제18권2호
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• pp.66-76
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• 2017

Background and Objectives: Although an anterior linear ablation is an effective lesion set in radiofrequency catheter ablation (RFCA) for longstanding persistent atrial fibrillation (L-PeAF), its durability for bidirectional block (BDB) is only about 60% at repeat procedure. We hypothesized that changes in electrocardiogram (ECG) may predict an anterior line block state and the clinical outcome of L-PeAF ablation. Subjects and Methods: We studied 304 L-PeAF patients (77% male, $60{\pm}10yrs$), who consistently underwent RFCA Dallas lesion set (circumferential pulmonary vein isolation, posterior box lesion, and anterior line) protocol with subsequent comparison of pre-procedural and post-procedural P wave axes, and one year follow-up (n=205) sinus rhythm (SR) ECGs. Results: 1. P wave axis shifted inferiorly at immediate post-procedure (p<0.001), and was independently correlated with BDB of anterior line (${\ss}=10.4$, 95% confidence interval [CI] 2.79-17.94, p=0.008). 2. The degree of post-procedural inferior shift of P wave axis did not reflect clinical recurrence within one-year (n=205, p=0.923), potentially due to conduction recovery of an anterior line. However, among 160 patients without clinical recurrence within one-year, P wave axis at one-year ECG was independently associated with very late recurrence of AF after one-year (n=160, hazard ratio [HR] 0.98; 95% CI 0.97-0.99, p=0.001), during $45.6{\pm}16.7$ months of follow-up. 3. Among 22 patients who underwent repeat procedures, P wave axis shift was more significant in patients with maintained BDB of an anterior line than in those without (p=0.015). Conclusion: An inferior shift of P wave axis reflects the achievement and the maintenance of an anterior line BDB, and is associated with better long-term clinical outcome after catheter ablation for L-PeAF based on Dallas lesion set.

• 대한토목학회논문집
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• 제26권2B호
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• pp.131-137
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• 2006

본 연구에서는 기존 매개변수적 수문시계열 예측모형을 보완하고자 Singular Spectrum Analysis(SSA)와 Linear Recurrent Formula를 결합한 모형을 제안하였다. SSA는 주로 시계열에 내재해 있는 구성성분을 추출하기 위한 목적으로 많이 이용되고 있다. 이러한 관점에서 본 연구에서는 엘니뇨 및 라니냐 등의 기상현상과 수문사상의 상관성 분석에 주로 적용되고 있는 SSA와 시계열 예측을 위해서 Linear Recurrence Formula를 결합한 예측 모형을 월단위의 수위와 유입량 시계열 자료를 대상으로 적용성 및 타당성을 검토해 보았다. 모형을 통해 수문시계열을 모의한 결과 전체적인 통계적인 특성 및 시각적인 검토에서 실측자료와 매우 유사한 모의가 가능하였으며 실측 자료를 바탕으로 Blind Forecasting을 실시한 결과 2가지 예에서 모두 1년 정도의 예측구간에서 합리적인 결과를 제시하여 주었다. 따라서 단기예측을 수문모형으로서 적용이 가능할 것으로 사료된다.