자동차용 판재성형 해석 적용을 위한 다중 스케일 마찰 모델 개발 및 평가

학위논문(박사) -- 서울대학교대학원 : 공과대학 재료공학부, 2022.2. 이명규.Sheet metal forming of advanced high strength steels (AHSS) has drawn significant attentions in automotive industry for their improved fuel efficiency by lightweightness and passenger safety by higher strength. However, the manufacturing of automotive parts with the AHSS accompanies inferior springback and formability compared to the conventional lower strength steels, which results in more time consuming trial and error in the tool design stage. To overcome this challenges in applying the AHSS to the automotive parts, finite element simulations have been commonly used as a numerical tool for predicting springback and formability of sheet metal parts prior to real try-out. Accurate modeling of finite element simulation in sheet metal forming process requires reliable numerical techniques, constitutive models, realistic boundary conditions, etc. Among these, the friction is one of important factors to determine the accuracy of the simulation, but it has been overlooked in most simulations. The frictional behavior in sheet metal forming is known to be very complex and depend on various parameters such as surface roughness, contact pressure, sliding velocity, lubrication condition, etc. However, it is a common practice to use the simplest Coulomb friction law in the finite element modeling. In the present study, a microscale asperity based friction model is further modified by imposing new model parameters for satisfying force equilibrium between contact surfaces. In addition, a geometrical shape model of the tool surface is newly proposed to determine the plowing effect of the friction. The tool geometry is modeled based on primary summits in tool height distribution determined by the measured wavelength, rather than the summits dependent on the resolution of surface measurement instrument. The friction models are required not only in the preceding boundary lubrication condition, but also in the mixed-boundary lubrication condition where sufficient lubrication exists in non-contacting surface valleys. The hydrodynamic friction model uses a load-sharing concept that considers the lubrication area and metal-to-metal contact separately. In this study, the hydrodynamic friction model is combined with the boundary lubrication friction model to account for the friction in the mixed lubrication domain. The lubricant film thickness, calculated as the volume of non-contacting surface valleys, is used to realize the coupling. The film lubrication behavior is implemented by the finite element coding of the Reynolds equation, which enables the calculation of the hydrodynamic pressure. To validate the boundary lubrication friction model, the calculated friction coefficient and the measured friction coefficient are compared according to the contact pressure under boundary lubrication conditions. Also, the boundary lubrication friction model is verified by the finite element simulation that is applied to the U-draw/bending process. Finally, the boundary lubrication friction model and the mixed boundary lubrication friction model are applied to the finite element simulation of the newly developed press-forming process, which represents the influence of various variables such as contact pressure, sliding speed and lubrication. The results of the validations show that the developed multi-scale friction models and their implementation can be efficiently used to the sheet metal forming simulations where the frictional behavior is critical for the quality of the automotive parts.AHSS(고장력강판)의 판금 성형은 경량화에 의한 연비 향상과 고강도화에 의한 승객 안전으로 자동차 산업에서 큰 주목을 받고 있습니다. 그러나 AHSS를 이용한 자동차 부품 제조는 기존의 저강도 강재에 비해 스프링백 및 성형성이 좋지않기에 툴 설계 단계에서 시행착오가 더 많이 발생하게 됩니다. 자동차 부품에 AHSS를 적용할 때 이러한 문제를 극복하기 위해 유한 요소 시뮬레이션은 실제 시험 전에 판재 성형 부품의 스프링백 및 성형성을 예측하기 위한 수치해석적 도구로 일반적으로 사용되었습니다. 판재 성형 공정에서 유한 요소 시뮬레이션의 정확한 모델링은 신뢰할 수 있는 수치해석적 기술, 구성 방정식, 정확한 경계 조건 등이 필요합니다. 이 중 마찰은 시뮬레이션의 정확도를 결정하는 중요한 요소 중 하나이지만 대부분의 시뮬레이션에서 간과되어 왔습니다. 판재 성형에서 마찰 거동은 매우 복잡하고 표면 거칠기, 접촉 압력, 미끄럼 속도, 윤활 조건 등과 같은 다양한 매개변수에 따라 달라지는 것으로 알려져 있습니다. 그러나, 대부분의 유한 요소 해석에서 가장 간단한 쿨롱 마찰 법칙을 사용하는 것이 일반적입니다. 본 연구에서는 접촉면 사이의 힘 평형을 만족시키기 위해 새로운 모델 매개변수를 부과하여 마이크로 스케일 돌기 기반 마찰 모델을 추가로 수정했습니다. 또한 마찰의 쟁기질 효과를 결정하기 위해 툴 표면의 기하학적 형상 모델이 새로 제안되었습니다. 툴 형상은 표면 측정 장비의 분해능에 의존하는 정점이 아니라 측정된 파장에 의해 결정되는 툴표면 높이 조도의 서밋을 기반으로 모델링됩니다. 마찰모델은 경계윤활조건뿐만 아니라 충분한 윤활이 존재하는 혼합경계윤활조건에서도 필요하다. 유체역학적 마찰 모델은 윤활 영역과 금속 대 금속 접촉을 별도로 고려하는 하중 공유 개념을 사용합니다. 본 연구에서는 유체역학적 마찰 모델을 경계 윤활 마찰 모델과 결합하여 혼합 윤활 영역의 마찰을 설명합니다. 비접촉 표면 밸리의 부피로 계산된 윤활유 필름 두께는 커플링을 구현하는 데 사용됩니다. 필름 윤활 거동은 유체역학적 압력의 계산을 가능하게 하는 Reynolds 방정식의 유한 요소 방법을 사용해 구현됩니다. 경계 윤활 마찰 모델을 검증하기 위해 경계 윤활 조건에서 접촉 압력에 따라 계산된 마찰 계수와 측정된 마찰 계수를 비교합니다. 또한 경계 윤활 마찰 모델은 U-draw/bending 과정에 적용된 유한 요소 시뮬레이션을 통해 검증되었습니다. 마지막으로 경계 윤활 마찰 모델과 혼합 경계 윤활 마찰 모델을 새로 개발된 프레스 성형 공정의 유한 요소 시뮬레이션에 적용했는데, 이는 접촉 압력, 미끄럼 속도 및 윤활과 같은 다양한 변수의 영향을 나타냅니다. 검증 결과는 개발된 다중 스케일 마찰 모델과 그 구현이 마찰 거동이 자동차 부품 품질에 중요한 판재 성형 시뮬레이션에 효율적으로 사용될 수 있음을 보여줍니다.1. Introduction 1 1.1. Sheet metal forming and deep drawing process 1 1.2. Motivation and objective 2 1.3. Literature review 5 1.3.1. Friction modeling on the boundary lubrication condition 6 1.3.2. Friction modeling on the mixed-boundary lubrication condition 22 2. Friction model in boundary lubrication 35 2.1. Framework of friction model in boundary lubrication 35 2.2. Statistical contact model for describing surface deformation 38 2.2.1. Assumptions for modeling 39 2.2.2. Flattening of workpiece asperity due to normal load 41 2.2.3. Flattening of workpiece asperity due to normal load and sliding 48 2.2.4. Flattening of workpiece asperity due to normal load and bulk strain 50 2.3. Friction model through a new approach 53 2.3.1. An elliptical paraboloid asperity model 53 2.3.2. A tool geometry model 56 3. Friction model in mixed-boundary lubrication 65 3.1. Overview of the mixed-boundary friction model (Hol [106]) 67 3.2. Finite element modeling for film fluid behavior 71 3.3. Verification of the developed finite element modeling 75 4. Application of boundary lubrication and mixed-boundary lubrication friction model to sheet metal forming process 82 4.1. Friction model parameters 82 4.1.1. Material properties 82 4.1.2. Surface data 83 4.1.3. Friction experiments 86 4.2. Application to sheet metal forming processes under non-lubrication conditions 91 4.2.1. Application to U-draw/bending simulation 94 4.2.2. Application to prototype press-forming process without lubricant 105 4.3. Application to sheet metal forming processes under lubrication conditions 116 5. Conclusions 129 Reference 134박

Focused on the Role of Surprise, Threat, and Anthropomorphism

학위논문 (석사) -- 서울대학교 대학원 : 경영대학 경영학과, 2020. 8. 이경미.Art has long been considered a creative domain that is exclusive to human beings, but now people are exposed to artworks created by artificial intelligence (AI). AI can be an autonomous artist and also collaborate with other human artists. It is becoming more important to understand how people feel and think toward artworks created by AI because AI technology is rapidly developing, and AI is seeking to take over domains that are considered to be exclusive to humans. The current research examines whether consumers emotion of interest differs based on the types of artist(s) (AI artist vs. AI and human collaboration vs. human artist) and further examines the effect of anthropomorphism. In study 1, it is proposed that consumers emotion of interest will differ whether the artworks are created by (1) an AI artist, (2) a collaboration between an AI artist and a human artist, or (3) a human artist. Surprise and perceived threat to human uniqueness are suggested as mediators for explaining the effect of artist type on consumers interest. In study 1, 473 participants showed the highest interest when the artist was AI and the lowest interest when the artist was human. There was a significant difference in interest between the AI condition and the human condition. But there was no significant difference in interest between the AI condition and the collaboration condition, and between the collaboration condition and the human condition. The effect of artist type on consumers interest is driven by surprise and perceived threat to human uniqueness. In study 2, it is proposed that consumers interest in the artists paintings will differ whether the artist is (1) an anthropomorphic AI, (2) a non-anthropomorphic AI, or (3) a human. This effect is suggested to be serially mediated by surprise and interest in the artist. In study 2, 290 participants showed higher interest in anthropomorphic AIs paintings than a non-anthropomorphic AIs or human artists paintings. But there was no significant difference in consumers interest in the artists paintings between the non-anthropomorphic condition and the human artist condition. Results support that the effect of anthropomorphism on consumers interest in the artists paintings is serially mediated by surprise and interest in the artist. This research makes theoretical contributions to the literature on AI and marketing by providing information that people are surprised but also threatened by AI art. Consequently, people are interested in art created by AI more than art created by other types of artists. This research makes another theoretical contribution by identifying the underlying psychological mechanisms that are affective and cognitive. The effect of anthropomorphism also suggests that people feel more interest in anthropomorphic AIs paintings than humans or non-anthropomorphic AIs. This research also has a practical implication because companies that make AI art or conduct AI art projects can establish strategic plans for those who may be most interested in AI artworks.최근 들어 사람들은 인공지능이 창작한 예술 작품에 더 노출되고 있다. 기술이 빠르게 발전하고 인공지능이 일반 대중에게 더 친숙해지고 있기 때문에 사람들이 인공지능으로 만든 예술 작품에 대해 어떻게 느끼고 생각하는지 이해하는 것이 중요해지고 있다. 특히 예술은 오랜 시간 동안 인간의 고유한 창작 영역으로 여겨져 왔기 때문에 연구의 필요성은 커지고 있다. 본 연구는 (1) 예술가의 유형 (인공지능 vs. 인공지능과 인간 간의 협업 vs. 인간)과 (2) 인공지능 예술가가 의인화된 정도 (의인화된 인공지능 vs. 의인화되지 않은 인공지능 vs. 인간)가 소비자의 흥미(interest)에 미치는 영향을 확인하고자 한다. 연구 1에서는 소비자들의 흥미가 예술가의 유형에 따라 다르게 나타나는지 살펴보고자 한다. 구체적으로, 예술가가 인공지능일 때 흥미가 가장 크게 나타나고 예술가가 인간일 때 흥미가 가장 낮게 나타날 것으로 예상된다. 예술가의 유형이 소비자의 흥미에 미치는 영향을 매개하는 변수로써 놀라움과 인간의 고유성에 대한 위협감을 제시하고자 한다. 연구 1 (n = 473)은 예술가의 유형이 소비자들의 흥미에 미치는 효과를 검증하였다. 참가자들의 흥미는 인공지능, 협업, 인간 예술가 순으로 컸으며, 인공지능 조건과 인간 조건 사이에서 유의미한 차이가 있는 것으로 나타났다. 그러나 참가자들의 흥미는 인공지능 조건과 협업 조건, 그리고 협업 조건과 인간 조건 사이에서 큰 차이가 없는 것으로 나타났다. 한편으로, 예술가 유형이 소비자의 흥미에 미치는 영향은 놀라움과 인간의 고유성에 대한 위협감에 의해 매개되었다. 구체적으로, 놀라움과 인간의 고유성에 대한 위협감은 예술가가 인공지능일 때 가장 높았고, 인간일 때 가장 낮았다. 연구 2에서는 예술가가 의인화된 정도에 따라 소비자들의 흥미가 달라지는지 확인하고자 한다. 소비자들의 흥미는 예술가가 의인화된 인공지능일 때 가장 클 것이며, 의인화의 정도가 예술가의 작품에 대한 소비자의 흥미에 미치는 영향은 놀라움과 예술가에 대한 흥미에 의해 연속적으로 매개될 것으로 예상된다. 연구 2 (n = 290)는 의인화된 인공지능 예술가의 작품에 대한 소비자들의 흥미에 미치는 영향을 살펴보았다. 참가자들은 의인화되지 않은 인공지능이나 인간의 예술 작품보다 의인화된 인공지능의 작품에 더 큰 흥미를 보였다. 이러한 주효과는 놀라움과 예술가에 대한 흥미에 의해 연속적으로 매개됨을 확인하였다. 이 연구는 인공지능 예술에 대한 소비자들의 감정적 그리고 인식적 반응을 분석하였다. 특히, 예술가의 유형이 소비자의 흥미에 미치는 효과는 놀라움과 인간의 고유성에 대한 위협감에 의해 매개되었다. 또한, 의인화가 예술가의 작품에 대한 소비자의 흥미에 미치는 효과는 놀라움과 예술가에 대한 흥미에 의해 매개된다는 정보를 제공함으로써 인공지능과 마케팅에 관한 문헌에 기여한다. 결과적으로 사람들은 인공지능이 창작한 작품에 흥미를 가지며, 특히 의인화된 인공지능 예술가일 경우 의인화되지 않은 인공지능과 인간이 예술가일 때보다 소비자들의 흥미를 더 이끌어낸다는 점을 확인하였다. 인공지능 예술을 창작하거나 인공지능 예술 프로젝트를 진행하는 기업들은 이 정보를 바탕으로 효과적인 전략을 세울 수 있다는 점에서 이 연구는 실질적인 시사점을 보이고 있다.I. INTRODUCTION 1 II. THEORETICAL BACKGROUND 4 2.1 Computational Creativity 4 2.2 Artificial Intelligence Art 5 2.3 Surprise and Interest – Incongruent Emotions 6 2.4 Perceived Threat to Human Uniqueness 9 2.5 Anthropomorphism 10 III. RESEARCH MODEL 13 3.1 Hypotheses 13 3.2 Overview of Studies 15 IV. STUDY 1 17 4.1 Method 17 4.2 Results and Discussion 20 V. STUDY 2 24 5.1 Method 24 5.2 Results and Discussion 27 VI. GENERAL DISCUSSION 31 6.1 Theoretical and Practical Implications 31 6.2 Limitations and Future Research 33 VII. REFERENCES 35 VIII. APPENDIX 43 요약(국문초록) 50Maste

Automatic Grading of Stroke Symptoms for Rapid Assessment Using Optimized Machine Learning and 4-Limb Kinematics: Clinical Validation Study

Background: Subtle abnormal motor signs are indications of serious neurological diseases. Although neurological deficits require fast initiation of treatment in a restricted time, it is difficult for nonspecialists to detect and objectively assess the symptoms. In the clinical environment, diagnoses and decisions are based on clinical grading methods, including the National Institutes of Health Stroke Scale (NIHSS) score or the Medical Research Council (MRC) score, which have been used to measure motor weakness. Objective grading in various environments is necessitated for consistent agreement among patients, caregivers, paramedics, and medical staff to facilitate rapid diagnoses and dispatches to appropriate medical centers. Objective: In this study, we aimed to develop an autonomous grading system for stroke patients. We investigated the feasibility of our new system to assess motor weakness and grade NIHSS and MRC scores of 4 limbs, similar to the clinical examinations performed by medical staff. Methods: We implemented an automatic grading system composed of a measuring unit with wearable sensors and a grading unit with optimized machine learning. Inertial sensors were attached to measure subtle weaknesses caused by paralysis of upper and lower limbs. We collected 60 instances of data with kinematic features of motor disorders from neurological examination and demographic information of stroke patients with NIHSS 0 or 1 and MRC 7, 8, or 9 grades in a stroke unit. Training data with 240 instances were generated using a synthetic minority oversampling technique to complement the imbalanced number of data between classes and low number of training data. We trained 2 representative machine learning algorithms, an ensemble and a support vector machine (SVM), to implement auto-NIHSS and auto-MRC grading. The optimized algorithms performed a 5-fold cross-validation and were searched by Bayes optimization in 30 trials. The trained model was tested with the 60 original hold-out instances for performance evaluation in accuracy, sensitivity, specificity, and area under the receiver operating characteristics curve (AUC). Results: The proposed system can grade NIHSS scores with an accuracy of 83.3% and an AUC of 0.912 using an optimized ensemble algorithm, and it can grade with an accuracy of 80.0% and an AUC of 0.860 using an optimized SVM algorithm. The auto-MRC grading achieved an accuracy of 76.7% and a mean AUC of 0.870 in SVM classification and an accuracy of 78.3% and a mean AUC of 0.877 in ensemble classification. Conclusions: The automatic grading system quantifies proximal weakness in real time and assesses symptoms through automatic grading. The pilot outcomes demonstrated the feasibility of remote monitoring of motor weakness caused by stroke. The system can facilitate consistent grading with instant assessment and expedite dispatches to appropriate hospitals and treatment initiation by sharing auto-MRC and auto-NIHSS scores between prehospital and hospital responses as an objective observation.ope

Factors Associated with Early Hospital Arrival in Patients with Acute Ischemic Stroke.

BACKGROUND AND PURPOSE: Factors associated with early arrival may vary according to the characteristics of the hospital. We investigated the factors associated with early hospital arrival in two different stroke centers located in Korea and Japan. METHODS: Consecutive patients with ischemic stroke arrived hospital within 48 hours of onset between January 2011 and December 2012 were identified and the clinical and time variables were retrieved from the prospective stroke registries of Severance Hospital of Yonsei University Health System (YUHS; Seoul, Korea) and National Cerebral and Cardiovascular Center (NCVC; Osaka, Japan). Subjects were dichotomized into early (time from onset to arrival ≤4.5 hours) and late (>4.5 hours) arrival groups. Univariate and multivariate analyses were performed to evaluate factors associated with early hospital arrival. RESULTS: A total of 1,966 subjects (992 from YUHS; 974 from NCVC) were included in this study. The median time from onset to arrival was 6.1 hours [interquartile range, 1.7-17.8 hours]. In multivariate analysis, the factors associated with early arrival were atrial fibrillation (Odds ratio [OR], 1.505; 95% confidence interval [CI], [1.168-1.939]), higher initial National Institute of Health Stroke Scale scores (OR, 1.037; 95% CI [1.023-1.051]), onset during daytime (OR, 2.799; 95% CI [2.173-3.605]), and transport by an emergency medical service (OR, 2.127; 95% CI [1.700-2.661]). These factors were consistently associated with early arrival in both hospitals. CONCLUSIONS: Despite differences between the hospitals, there were common factors related to early arrival. Efforts to identify and modify these factors may promote early hospital arrival and improve stroke outcome.ope

Low Hypoperfusion Intensity Ratio Is Associated with a Favorable Outcome Even in Large Ischemic Core and Delayed Recanalization Time

In ischemic brain tissue, hypoperfusion severity can be assessed using the hypoperfusion intensity ratio (HIR). We evaluated the link between HIR and clinical outcomes after successful recanalization by endovascular treatment. We retrospectively reviewed 162 consecutive patients who underwent endovascular treatment for intracranial large vessel occlusion. The HIR was calculated using an automated software program, with initial computed tomography perfusion images. The HIR was compared between patients with and without favorable outcomes. To observe the modifying effect of the HIR on the well-known major outcome determinants, regression analyses were performed in the low and high HIR groups. The median HIR value was significantly lower in patients with a favorable outcome, with an optimal cut-off point of 0.54. The HIR was an independent factor for a favorable outcome in a specific multivariable model and was significantly correlated with the Alberta Stroke Program Early Computed Tomography Score (ASPECTS). In contrast to the high HIR group, the low HIR group showed that ASPECTS and onset-to-recanalization time were not independently associated with a favorable outcome. Finally, the low HIR group had a more favorable outcome even in cases with an unfavorable ASPECTS and onset-to-recanalization time. The HIR could be useful in predicting outcomes after successful recanalization.ope

Lenticulostriate Artery Involvement is Predictive of Poor Outcomes in Superficial Middle Cerebral Artery Territory Infarctio

PURPOSE: Patients with superficial middle cerebral artery (MCA) territory infarction may have concomitant lenticulostriate artery (LSA) territory infarction. We investigated the mechanisms thereof and the outcomes of patients with superficial MCA territory infarction according to the presence or absence of LSA involvement. MATERIALS AND METHODS: Consecutive patients with first-ever infarction in the unilateral superficial MCA territory were included in this study. They were divided into the superficial MCA only (SM) group and the superficial MCA plus LSA (SM+L) group. RESULTS: Of the 398 patients, 84 patients (21.1%) had LSA involvement (SM+L group). The SM+L group more frequently had significant stenosis of the proximal MCA or carotid artery and high-risk cardioembolic sources. Stroke severity and outcomes were remarkably different between the groups. The SM+L group showed more severe neurologic deficits (National Institute of Health Stroke Scale score 10.8±7.1 vs. 4.0±5.0, p2) at 3 months was more common in the SM+L group (64.3% vs. 15.9%, p<0.001). During a mean follow-up of 26 months, 67 patients died. All-cause (hazard ratio, 2.246) and stroke (hazard ratio, 9.193) mortalities were higher in the SM+L group than the SM group. In multivariate analyses, LSA involvement was an independent predictor of poor functional outcomes and stroke mortality. CONCLUSION: LSA territory involvement is predictive of poor long-term outcomes in patients with superficial MCA territory infarction.ope

Association of Substantia Nigra Degeneration with Poor Neurological Recovery in Basal Ganglia Infarctions

ope

Coronary Calcium Score for the Prediction of Asymptomatic Coronary Artery Disease in Patients With Ischemic Stroke

Purpose: Many patients with ischemic stroke have concomitant coronary artery disease (CAD). However, it remains unclear which stroke patients should undergo evaluation for asymptomatic CAD, and which screening tools are appropriate. We investigated the role of coronary artery calcium (CAC) score as a screening tool for asymptomatic but severe CAD in acute stroke patients. We determined the selection criteria for CAC screening based on risk factors and cerebral atherosclerosis. Materials and Methods: The present study included consecutive patients with acute stroke who had undergone cerebral angiography and multi-detector computed tomography coronary angiography. Severe CAD was defined as left main artery disease or three-vessel disease. Enrolled patients were randomly assigned to two sets; a set for developing selection criteria and a set for validation. To develop selection criteria, we identified associated factors with severe CAD regarding clinical factors and cerebral atherosclerosis. CAD predictability of selection criteria with the CAC score was calculated. Results: Overall, 2,658 patients were included. Severe CAD was present in 360 patients (13.5%). CAC score was associated with CAD severity (P 65 years [odds ratio (95% confidence interval), 2.62 (1.93-3.55)], male sex (1.81 [1.33-2.46]), dyslipidemia (1.77 [1.25-2.61]), peripheral artery disease (2.64 [1.37-5.06]) and stenosis in the cervicocephalic branches, including the internal carotid (2.79 [2.06-3.78]) and vertebrobasilar arteries (2.08 [1.57-2.76]). We determined the combination of clinical and arterial factors as the selection criteria for CAC evaluation. The cut-off criterion was two or more elements of the selection criteria. The area under the curve (AUC) of the selection criteria was 0.701. The AUC significantly improved to 0.836 when the CAC score was added (P < 0.001). In the validation set (N = 798), the AUC of the selection criteria only was 0.661, and that of the CAC score was 0.833. The AUC of the selection criteria + CAC score significantly improved to 0.861(P < 0.001). Conclusion: The necessity for CAC evaluation could be determined based on the presence of risk factors and significant stenosis of the cervicocephalic arteries. CAC evaluation may be useful for screening for severe CAD in stroke patients.ope

Effect and Safety of Rosuvastatin in Acute Ischemic Stroke

BACKGROUND AND PURPOSE: The benefit of statins in acute stroke remains uncertain. Statins may prevent stroke recurrence during the acute stage of stroke via pleiotropic effects. However, statins may increase the risk of intracerebral hemorrhage. We investigated the effect and safety of rosuvastatin in acute stroke patients. METHODS: This randomized, double-blind, multi-center trial compared rosuvastatin 20 mg and placebo in statin-naïve stroke patients who underwent diffusion-weighted imaging (DWI) within 48 hours after symptom onset. The primary outcome was occurrence of new ischemic lesions on DWI at 5 or 14 days. RESULTS: This trial was stopped early after randomization of 316 patients due to slow enrollment. Among 289 patients with at least one follow-up imaging, the frequency of new ischemic lesions on DWI was not different between groups (rosuvastatin: 27/137, 19.7% vs. placebo: 36/152, 23.6%) (relative risk 0.83, 95% confidence interval 0.53-1.30). Infarct volume growth at 5 days (log-transformed volume change, rosuvastatin: 0.2±1.0 mm(3) vs. placebo: 0.3±1.3 mm(3); P=0.784) was not different, either. However, hemorrhagic infarction or parenchymal/subarachnoid hemorrhage on gradient-recalled echo magnetic resonance imaging occurred less frequently in the rosuvastatin group (6/137, 4.4%) than the placebo group (22/152, 14.5%, P=0.007). Among 314 patients with at least one dose of study medication, progression or clinical recurrence of stroke tended to occur less frequently in the rosuvastatin group (1/155, 0.6% vs. 7/159, 4.4%, P=0.067). Adverse events did not differ between groups. CONCLUSIONS: The efficacy of rosuvastatin in reducing recurrence in acute stroke was inconclusive. However, statin use was safe and reduced hemorrhagic transformation.ope

Long-Term Mortality According to the Characteristics of Early Neurological Deterioration in Ischemic Stroke Patients

PURPOSE: Although early neurological deterioration (END) during the acute stroke period is known to be associated with poor functional outcomes, there is little data regarding the impact of END on long-term outcomes according to the characteristics of END. The aim of this study was to investigate whether there are differences in long-term mortality according to the characteristics of END among acute ischemic stroke or transient ischemic attack patients. MATERIALS AND METHODS: END was defined as any increase (≥1) in National Institute of Health Stroke Scale score within 7 days after admission. We assessed the characteristics of END, such as the etiology and severity of END, as well as recovery after END. The relationship between 30-day or long-term mortality and each characteristic of END was investigated using multiple logistic analysis or Cox regression model. RESULTS: Among 2820 patients, END was observed in 344 patients (12.2%). After adjustment for age, sex, underlying cardiovascular diseases, stroke severity, and stroke subtypes, END was associated with long-term mortality, whether it was mild or severe and whether or not it was followed by recovery. However, 30-day mortality was strongly related to the severity of END or the absence of recovery after END. Among the causes of END, recurrent stroke and medical illness were related to 30-day mortality, as well as long-term mortality, while brain herniation and intracranial hemorrhagic complications were only associated with 30-day mortality. CONCLUSION: The results of the present study demonstrated that END is associated with higher mortality and the effects of END on short-term and long-term mortality depend on END characteristics.ope