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평면상 응고계면의 형태학적 안정성에 대한 비평형 열역학적 고찰
한정호,이동희,최국선 대한금속재료학회(대한금속학회) 1986 대한금속·재료학회지 Vol.24 No.1
This theoretical study was carried out on the determination of the morphological stability criterion of planar solid-liquid interface. The system of a directional solidification under the nonequilibrium steady-state was defined as a continuous open system and the basic assumptions for the perturbation on the planar interface were introduced in order to analyze the pattern formation. The pattern formation was also interpreted by applying the marginal stability hypothesis. The results obtained can be summarized as follows. 1. The morphological stability criterion was T_mΓω²+ G_L-mG_c $gt; 0 and this could be reduced to the CS criterion. 2. The critical wavelength of perturbation, λ_c, was calculated by applying the marginal stability. From this result, it could be predicted that the shapes of the interface were changed with the wave length of perturbation. 3. It was suggested that the cell size, ℓ, can be limited by the critical wavelength of perturbation.
급성 심근경색증으로 재관류 치료를 시행받은 환자에서 내원시 백혈구 수와 심근 손상의 관계
한정호,연태진,홍의실,윤수인,문기원,김학의,한지숙,김기석,배장환,황경국,김동운,조명찬 대한심장학회 2004 Korean Circulation Journal Vol.34 No.8
Background and Objectives:The presence of leukocytosis in patients with acute myocardial infarction (AMI) has been reported to be related to the extent of MI and with the prognosis. However, whether the leukocytosis itself is a cause or result of the myocardial injury has not been determined. The relationship between the leukocyte count and the extent of myocardial injury was investigated in patients with AMI that had undergone reperfusion therapy. Subjects and Methods:Patients with AMI that had undergone thrombolysis (n=60) or primary PCI (n=36) were included. The initial leukocyte counts were analyzed with regard to the peak and initial CK-MB levels. The relationship between leukocytosis and the time elapsed from the onset of symptoms, infarct related coronary arteries and the proximity of the lesions were also investigated. Results:In both groups, the initial leukocyte count did not show a significant relationship with the initial CK-MB level or the time elapsed from symptoms onset, which could be an indication of the extent of early myocardial injury. Furthermore, no significant relationship was shown with the infarct related coronary artery or proximity of the lesion. However, a relationship was shown with the maximum CK-MB level, which could be an indication of the extent of myocardial injury following reperfusion therapy in both groups (p<0.01). Conclusion:This study suggests that the initial leukocyte count in patients with AMI might is an important prognostic factor that determines the extent of myocardial injury following reperfusion therapy, rather than being a simple indicator of the extent of early myocardial injury. 배경 및 목적: 급성 심근경색증 환자의 내원시 백혈구증가증은 심근경색의 크기와 양의 상관관계가 있으며, 환자의 불량한 예후와 연관이 있다고 알려져 있다. 그러나, 손상된 심근의 양이 많을수록 백혈구수가 증가하는지 혹은 증가된 백혈구가 더 큰 심근 손상을 유발하는지는 알려져 있지 않다. 본 연구는 급성 심근경색증으로 혈전용해치료를 시행 받은 환자와 관동맥중재술을 시행 받은 환자를 대상으로 응급실 내원 당시의 백혈구수와 재관류 치료 후의 심근 손상 정도와의 연관관계를 알아보고자 하였다. 방 법: 충북대병원 응급실을 방문하여 급성 심근경색증으로 진단 받은 환자 중 혈전용해치료(n=60) 혹은 관동맥중재술(n=36)을 시행 받은 환자들을 대상으로 하였다. 모든 환자들을 대상으로 내원시 말초혈액 백혈구수를 측정하였으며, 이를 증상 발현부터 응급실 내원시까지의 경과 시간, 내원시 Creatine Kinase(CK)-MB 수치, 재관류 치료 후 CK-MB의 최고치 및 상승치, 경색 관련 혈관 및 혈관 내 병변의 위치와 비교 분석하였다. 결 과: 혈전용해치료군과 관동맥중재술군 모두에서 내원시 백혈구수는 초기 심근 손상의 정도를 대변할 수 있는 내원시의 CK-MB 값 및 흉통의 발생부터 응급실에 도착할 때까지의 시간과는 유의한 상관관계가 없었고, 경색 관련 혈관 및 혈관 내 병변의 위치와도 유의한 상관관계를 보이지 않았다. 그러나, 양군 모두에서 내원시 백혈구수는 급성 심근경색증에 대한 재관류 치료 후의 심근 손상을 대변할 수 있는 입원 중 CK-MB의 최고치와 유의한 상관관계를 보였다(혈전용해치료군;r=0.34, p<0.01, 관동맥중재술군;r=0.45, p<0.01). 결 론: 급성 심근경색증 환자에서 응급실 내원시의 백혈구수는 초기 심근 손상의 정도에 의해 결정되는 단순한 변수라기보다는, 재관류 치료 후의 심근 손상의 정도를 결정하는 예후 인자중의 하나로 작용할 수도 있다고 생각된다.
Al-Ti-Ce 합금의 기계적 합금화 거동과 열적 안정성에 관한 연구
한정호,김선진,임준택 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.6
In order to investigate the effect of Ce on the thermal stability of Al Ti alloy, Al- 8wt.%(Ti+Ce) powders with different Ti to Ce atomic ratio were mechanically alloyed in an attritor. The steady state was obtained after 16 hours milling for all the alloys. The mechanically alloyed powders were vacuum hot pressed and isothermally aged for 100 hours at 400 550℃. The coarsening of A1- Ti intermetallic compounds was retarded by addition of Ce and the thermal stability was improved. The lattice parameter variations of Al-Ti-Ce intermetallic compounds were measured, and the addition of Ce increased the overall lattice mismatch between the intermetallic compound and Al matrix, and so the interfacial energy. Therefore, when considered the solubility and diffusivity of Ce in Al, it was considered that the low solid solubility of Ce in Al matrix was the major factor to the increased thermal stability of Al-Ti alloy.
한정호,윤소진,이혜선,박고은,임주희,신정은,은호선,박민수,이순민 연세대학교의과대학 2022 Yonsei medical journal Vol.63 No.7
Purpose: The aims of the study were to develop and evaluate a machine learning model with which to predict postnatal growthfailure (PGF) among very low birth weight (VLBW) infants. Materials and Methods: Of 10425 VLBW infants registered in the Korean Neonatal Network between 2013 and 2017, 7954 infantswere included. PGF was defined as a decrease in Z score >1.28 at discharge, compared to that at birth. Six metrics [area under the re ceiver operating characteristic curve (AUROC), accuracy, precision, sensitivity, specificity, and F1 score] were obtained at five timepoints (at birth, 7 days, 14 days, 28 days after birth, and at discharge). Machine learning models were built using four different tech niques [extreme gradient boosting (XGB), random forest, support vector machine, and convolutional neural network] to compareagainst the conventional multiple logistic regression (MLR) model. Results: The XGB algorithm showed the best performance with all six metrics across the board. When compared with MLR, XGBshowed a significantly higher AUROC (p=0.03) for Day 7, which was the primary performance metric. Using optimal cut-off points,for Day 7, XGB still showed better performances in terms of AUROC (0.74), accuracy (0.68), and F1 score (0.67). AUROC valuesseemed to increase slightly from birth to 7 days after birth with significance, almost reaching a plateau after 7 days after birth. Conclusion: We have shown the possibility of predicting PGF through machine learning algorithms, especially XGB. Such mod els may help neonatologists in the early diagnosis of high-risk infants for PGF for early intervention.