러시아의 크림반도 합병의 해양안보적 고찰

정민기,Jung, Min-ki 한국해양전략연구소 2023 해양안보 Vol.6 No.1

This study aims to review Russia's annexation of Crimea from a maritime security perspective. Based on a comprehensive analysis of Russia's national security perception, this study analyzed Russia's maritime security strategy and the security importance of the Black Sea and the Sea of Azov, and reviewed the annexation of Crimea from a maritime security perspective. The main argument of this study is as follows. Russia's annexation of Crimea was necessary for the successful fulfillment of Russia's maritime security strategy in the Black and Azov Seas. Russia's annexation of Crimea guarantees the activities of the Black Sea Fleet militarily from a maritime security point of view, secures a passage to the Atlantic Ocean to counter NATO's expansion. From a economic security point of view, Russia's annexation of Crimea was based on the strategic considerations to secure influence within the Black Sea economic bloc which guarantees stable production and transportation of natural resources and shipping.

세라믹 원료 장석광물의 미량성분 정량분석

정민기,임지수,이현아,김현구 한국분석과학회 2017 학술대회논문집 Vol.2017 No.5

2LO-1 Self-rearrangement of silicon nanoparticles embedded in micron carbon sphere framework for high-energy and long-life lithium-ion batteries

정민기 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1

Despite its highest theoretical capacity, the applications of the silicon anode are still limited by severe capacity fading, which is due to pulverization of the Si particles through volume change during charge and discharge. To deal with those complications, Si nanoparticles are embedded in micro-sized porous carbon spheres (Si-MCS) via a facile hydrothermal process, in order to provide a stiff carbon framework that functions as a cage to hold the pulverized silicon pieces. The carbon framework subsequently allows these silicon pieces to rearrange themselves in restricted domains within the sphere. Hence, it demonstrates excellent cyclability, high rate capability and high specific volumetric capacity on account of increased tap density. The lithium-ion battery using the new Si-MCS anode and commercial LiNi_0.6Co_0.2Mn_0.2O₂ cathode shows a high specific energy density which is considerably higher than that of commercial graphite anodes.

A study on kinematic changes in treadmill walking using AI-based overground walking controller

정민기 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

The treadmill is frequently used in gait analysis due to controlled and convenient experimental conditions. However, previous studies have analyzed differences in lower limb kinematics and kinetics between overground and treadmill walking. These differences have been reported that came from psychological causes such as fear, air resistance, visual information and treadmill speed errors due to human-treadmill interaction. The purpose of this study was to investigate kinematic differences between overground and treadmill walking, excluding psychological causes, through an AI-based gait controller in a dynamic simulation environment. The gait controller consists of a two-layer neural network, and it was trained by deep reinforcement learning to track a reference motion. The reference motion was made through the experiment of walking on the ground by a subject. This gait controller was tested overground walking and treadmill walking in the simulation. Comparing kinematics in overground walking and treadmill walking, the RMS difference of the knee flexion angle and hip flexion angle were 0.15 degrees and 0.12 degrees, respectively. The peak treadmill speed error during treadmill walking was 14 mm/s, which caused the kinematic difference.

NH₃-SCR에서 Sb 첨가에 따른 V/W/TiO₂ 촉매의 phoshphorous 피독 영향 연구

정민기,홍성창,문창진,이연진,김민수,신중훈,어은겸 한국공업화학회 2021 한국공업화학회 연구논문 초록집 Vol.2021 No.1

12주간 태권도 홈 트레이닝 프로그램이 스마트폰 과의존 비만아동의 건강체력과 면역기능에 미치는 영향

정민기 한국체육과학회 2020 한국체육과학회지 Vol.29 No.3

The present study is aimed at investigating the effects of 12 weeks Taekwondo home training program on health physical fitness and immuno function in obese chidren dependent on smart phones. Sixteen obese children dependent on smart phones were assigned in Taekwondo home training group(n=8), and control group(n=8). The Taekwondo home training program consisted of program 50min/session, 3 days each week for 12 weeks. The results of this study were as follow. First, in body composition and health physical fitness, weight(p<.01), lean body mass(p<.01), percent body fat(p<.001), body mass index (p<.001), modified curl-up(p<.01), 50m run(p<.01), standing long jump(p<.01), pacer(p<.01), and total flexibility(p<.01) had a statistically significant. Second, in smart phone dependent and immuno function, smart phone dependent(p<.01), immuno globulin A(p<.001), immuno globulin D(p<.01), immuno globulin G(p<.01), and immuno globulin M(p<.05) had a statistically significant. Third, body mass index and smart phone dependent(r=.700, p<.01), and immuno globulin D(r=.750, p<.01) showed a positive correlation while body mass index and immuno globulin A(r=-.651, p<.01) showed a negative correlation. Also, smart phone dependent and immuno globulin D(r=.548, p<.05) presented a positive correlation while smart phone dependent and immuno globulin A(r=-.623, p<.01), and immuno globulin M(r=-.547, p<.05) showed a negative correlation. In conclusion, these findings suggest that Taekwondo home training program may represent an effective intervention strategy for improving health physical fitness and smart phone dependent and immuno function in obese children dependent on smart phones.

청소년의 스마트폰 과의존 경향과 체질량지수 및 건강 체력과의 관계

정민기,김권민,정현훈,박상갑 한국사회체육학회 2019 한국사회체육학회지 Vol.0 No.78

Purpose: The purpose of this study is to examine the association of body mass index and health fitness according to smartphone usage levels among adolescents. Method: Data were analyzed for 1,509 students who responded to self-reported base cross-sectional survey relating to socio-demographic variables, smartphone usage status, and a short version of the international physical activity questionnaire. Results: The results of this study are as follows. 1) Prevalence rate of smartphone usage levels showed that 27.2% at Q1 (≤23) group, 26.8% at Q2 (24-29) group, 24.5% at Q3 (30-34) group, and 21.5% at Q4 (35≤) group. 2) In comparison with the smartphone usage levels was significantly more likely body mass index(≤19.98) crude model (OR, 0.73; 95% confidence interval [95%CI], 0.55-0.98; p<0.05) and multi-adjusted model (OR, 0.66; 95% confidence interval [95%CI], 0.49-0.89; p<.05). 3) In comparison with the smartphone usage levels was significantly more likely physical activity promotion system (≤63) crude model (OR, 1.45; 95% confidence interval [95%CI], 1.08-1.94; p<.05) and multi-adjusted model (OR, 1.59; 95% confidence interval [95%CI], 1.18-2.15; p<.05). Conclusion: In summary, the findings in this study confirm that significant associations are found between smartphone usage levels score and body mass index & physical activity promotion system among adolescents.

동적 HNS Risk Chart 설계에 관한 연구

정민기,이은방,윤종휘,하민재,김태형,이문진 해양환경안전학회 2017 해양환경안전학회 학술발표대회 논문집 Vol.2017 No.04

HNS 선박 최적항로 설정 기법 연구

정민기,이은방,윤종휘,이문진,강원수 해양환경안전학회 2018 해양환경안전학회 학술발표대회 논문집 Vol.2018 No.06

지주막낭종의 전산화단층촬영술

정민기 대한영상의학회 1988 대한영상의학회지 Vol.24 No.1

The preoperative diagnosis of intracranial arachnoid cysts has been simplified and made more rapid and accurate with computed tomography(CT) Using CT cisternography detailed anatomic and physiologic infor-mations of arachnoid cysts could be obtained. CT features of pathologically proven 21 arachnoid cysts that were examined at Chonnam National Universi-ty Hospital from June 1983 to May 1987 were analyzed. The results were as follows : 1.prevalent age group was the 1st decade (8 cases) and male to female ratio was 17:4. 2.Clinical features were related to the location of arachnoid cyst common symptoms were headache(53.3%) convulsion mental change and walking disturbance. 3.Locations of the arachnoid cyst were in supratentoral region (15 cases) most in middle cranial fossa (12 cases) and infratentoral region (6 cases) common at the retrocerebellar cisternal space (3cases). 4. Shapes of arachnoid cyst were biconvex with straight inner margin (8 cases) spherical (7 cases) simple biconvex (3 cases) and others (3 cases). 5. Size of thearachnoid cyst in the greatest dimension was ranged from 2 cm to 9 cm and commonly distributed between 3 cm to 5 cm (14 cases). 6. Of all 14 cases who did CT cisternography using metrizamide (11 cases) and iopamidol(3 cases) 2 cases had communication with the subarachnoid space.