나노 입자의 군집밀도를 이용한 고분자 나노복합재의 기계적 거동 예측에 대한 멀티스케일 연구

백경민,신현성,한진규,조맹효,Baek, Kyungmin,Shin, Hyunseong,Han, Jin-Gyu,Cho, Maenghyo 한국복합재료학회 2017 Composites research Vol.30 No.5

본 연구에서는 폴리프로필렌 내에 투입된 탄화규소 나노 입자들의 군집현상이 나노복합재의 역학적 거동에 미치는 영향을 고찰하기 위해 분자동역학 전산모사를 통해 얻은 정보를 연속체 역학 수준에 적용시키는 멀티스케일 해석을 수행하였다. 입자 간의 거리에 따른 계면 물성의 하락을 반영하는 모델을 이용하여, 다양한 군집 상황에 따른 고분자 나노복합재의 탄성거동 변화를 관찰하였다. 또한, 나노복합재의 기계적 거동에 영향을 미치는 주요 요인을 파악하여 군집밀도라는 새로운 지표를 정의하였다. 나노 입자의 군집밀도와 나노복합재의 탄성거동 간의 상관관계를 파악한 결과, 군집밀도의 값이 증가할수록 계면효과가 저하되어 최종적으로 나노복합재의 기계적 물성 상승이 억제되었다. 나노 입자의 랜덤분포를 고려한 해석을 통해, 동일한 군집밀도의 수치에 대해 나노복합재가 가질 수 있는 탄성계수의 범위를 파악할 수 있었다. 상관관계는 지수 함수형태로 표현될 수 있었으며, 이를 통해 나노 입자의 군집밀도를 이용하여 고분자 나노복합재의 기계적 거동을 효과적으로 예측 가능하다. In this study, multiscale analysis in which the information obtained from molecular dynamics simulation is applied to the continuum mechanics level is conducted to investigate the effects of clustering of silicon carbide nanoparticles reinforced into polypropylene matrix on mechanical behavior of nanocomposites. The elastic behavior of polymer nanocomposites is observed for various states of nanoparticulate agglomeration according to the model reflecting the degradation of interphase properties. In addition, factors which mainly affect the mechanical behavior of the nanocomposites are identified, and new index 'clustering density' is defined. The correlation between the clustering density and the elastic modulus of nanocomposites is understood. As the clustering density increases, the interfacial effect decreased and finally the improvement of mechanical properties is suppressed. By considering the random distribution of the nanoparticles, the range of elastic modulus of nanocomposites for same value of clustering density can be investigated. The correlation can be expressed in the form of exponential function, and the mechanical behavior of the polymer nanocomposites can be effectively predicted by using the nanoparticulate clustering density.

연하장애를 동반한 중풍환자 3례에서의 두침 및 전침의 효과

백경민,김민지,이현의,임승민,안정조,유호룡,조현경,김윤식,설인찬,Baek, Kyung-Min,Kim, Min-Ji,Lee, Hyon-Ui,Lim, Seung-Min,Ahn, Jung-Jo,Yoo, Ho-Ryong,Jo, Hyun-Kyung,Kim, Yoon-Sik,Seol, In-Chan 대한한방내과학회 2007 大韓韓方內科學會誌 Vol.28 No.3

Objectives : Although dysphagia is a common complication in stroke patients, there are few studies or reports about its treatment in oriental medicine. This study was to report the effects of scalp-acupuncture and electro-acupuncture in stroke patients with dysphagia. Methods : Three stroke patients with dysphagia hospitalized in our hospital were treated by scalp-acupuncture and electro-acupuncture simultaneously every day, 5 times a week for 4 weeks. Results : All of them showed constant improvement during the four weeks. Not only did their objective measures improve, but also their subjective symptoms such as throat discomfort, sputum, swallowing disturbance etc. Conclusions : This suggests that scalp-acupuncture and electro-acupuncture are quite effective when treating stroke patients with dysphagia. More clinical data and studies are to be done for efficient application.

가미자음강화탕(加味滋陰降火湯)이 SHR의 혈압에 미치는 영향

백경민,조현경,유호룡,김윤식,설인찬,Baek, Kyung-Min,Jo, Hyun-Kyung,Yoo, Ho-Rhyong,Kim, Yoon-Sik,Seol, In-Chan 대한한방내과학회 2006 大韓韓方內科學會誌 Vol.27 No.1

Objective : This study was done to investigate the effect of KJT on hypertension. Methods : Spontaneous Hypertensive Rats were sensitized and challenged with Kamijaeumganghwatang(KJT) for 5 weeks. Experimental group was treated with $200mg/day/2m{\ell}$ of KJT orally and control group was treated with $2m{\ell}/day$ of normal saline instead. Results : 1. KJT significantly showed significant protection against cytotoxicity and toxicity in the liver and the kidney. 2. KJT significantly decreased the blood pressure in SHR. 3. KJT significantly decreased the levels of aldosterone in SHR. 4. KJT significantly decreased the levels of dopamine, norepinephrine and epinephrine in SHR. 5. KJT significantly decreased the levels of sodium and potassium in SHR, but it did not decrease the levels of chloride in SHR. Levels of calcium in SHR increased, but only insignificantly. 6. KJT significantly decreased the levels of IL-6 in SHR, and significantly increased the levels of IL-10 in SHR. 7. For histological effects, KJT dillated capillary vessels in the kidney, significantly decreased eosinophilic changes in heart cells, and significantly decreased endothelial damage in the aorta. Conclusion: These results suggest that KJT is useful in treatment of hypertension.

예강지탕(銳降脂湯)이 고지혈증 SHR 및 항산화에 미치는 영향

백경민,Baek, Kyung-Min 대한한방내과학회 2010 大韓韓方內科學會誌 Vol.31 No.4

Objective : Yegangji-tang (YJT) is noted in China as effective medicine for hyperlipidemia. This experiment was performed to determine the effects of Yegangji-tang (銳降脂湯: YJT) on antioxidant activity and hyperlipidemia induced by hypercholesterolemic diet in mice. Methods : We observed three experimental groups: normal, control, and treatment. Rats were provided a normal diet in the normal group, and the other groups were provided a hypercholesterolemic diet to induce hyperlipidemia. After 2 weeks, YJT was treated to the treatment group. We observed the change of body and liver weight, change of serum total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides, lipid peroxidation and antioxidant activity of liver tissue, cholesterol gene revelation control efficiency, and histologic change of liver and abdominal aorta. Results : Total cholesterol, LDL cholesterol and triglycerides decreased significantly with YJT, whereas HDL cholesterol increased significantly. Lipid peroxidation decreased and antioxidant activity of the liver increased significantly. Gene revelation of ACAT and HMG-CoA reductase in hepatic tissue decreased significantly with YJT. We also found that tissue defects of the liver and abdominal aorta were controlled by YJT on histologic study. Conclusion : These results suggest that YJT might be effective in treatment and prevention of hyperlipidemia.

실시간 탄성초음파를 이용한 만성 뇌졸중 후 편마비 환자의 상지 강직에 대한 사암침 효과 연구

백경민,권동락,박기영,Baek, Kyung-Min,Kwon, Dong-Rak,Park, Gi-Young 대한한방내과학회 2014 大韓韓方內科學會誌 Vol.35 No.1

Objectives : To investigate the effects of Sa-am acupuncture on muscle architecture and elastic properties of the spastic elbow flexor and to evaluate the correlation between clinical findings and parameters of real-time sonoelastography (RTS) in patients with chronic post-stroke hemiparesis. Materials and Methods : Seven patients (five males, two females) with chronic post-stroke hemiparesis were included. Sa-am acupuncture of Ganseunggyeok (肝勝格: LU8 LR4 補, HT8 LR2 瀉) was applied to the unaffected side 3 times a week for 4 weeks. During each acupuncture treatment period, patients were requested to exercise their affected arm, and spasticity and functional recovery outcomes of the affected arm were evaluated before and after Sa-am acupuncture treatment. Clinical outcomes were assessed using motricity index (MI), modified Ashworth scale (MAS), Fugl-Meyer assessment scale (FMA) and modified Barthel index (MBI) for elbow flexor spasticity. RTS images indicate the relative hardness of the examined muscles ranged from red (hard) to purple (soft) for color-scale, and from black (hard) to white (soft) for hue scale. Color and hue histograms of the biceps brachii and brachialis were analyzed using Image J software, and median red, blue, and hue pixel intensity were obtained. Results : MI and FMA score significantly increased and MAS score significantly decreased (p<0.05). F-wave maximal amplitude of affected abductor pollicis brevis significantly decreased (p<0.05). Muscle thickness of affected brachialis significantly increased (p<0.05). Red and green pixel intensity of affected brachialis significantly decreased (p<0.05). Conclusions : Our study revealed that Sa-am acupuncture is effective as a useful and safe treatment for spasticity in chronic post-stroke hemiparesis.

샌드위치 워크벤치

백경민(Kyoung-Min Baek),손민정(Minjung Sohn),박주희(Joohee Park),남택진(Tek-Jin Nam) 한국HCI학회 2013 한국HCI학회 학술대회 Vol.2013 No.1

철강산업도시 포항지역 유해대기오염물질의 오염특성 ( I )

백경민(Kyung-Min Baek),서영교(Young-Kyo Seo),조병윤(Byoung-Yoon Cho),백성옥(Sung-Ok Baek) 한국대기환경학회 2018 한국대기환경학회지 Vol.34 No.2

누가 공공영역을 신뢰하는가?: 카자흐스탄의 사례1

백경민(Baek, Kyungmin) 계명대학교 사회과학연구소 2020 한국사회과학연구 Vol.39 No.3

1991년 소련으로부터 독립이후 카자흐스탄은 급속한 사회 경제적인 발전을 이룩했지만, 여전히 권위주의 정치체제를 유지하고 있다. 이러한 경제와 사회체제 사이의 모순은 카자흐스탄인들로부터 공공영역의 성과에 대해 상반된 평가를 추동할 수 있다. 본 논문에서는 공공영역에 대한 상반된 평가를 추동하는 사회심리적인 요인을 하나의 이론적 틀로 설명하려 한다. 특히 본 논문에서는 1991년 카자흐스탄의 독립 이후 카자흐스탄이 직면한 세계화의 물결 속에서 나타난 제도적 환경(Institutional Environment)의 변화가 공공영역에 대한 신뢰도에 영향을 미치는 중요한 요인이라고 주장하고자 한다. 최근 공개된 2014 세계가치관 조사(World Value Survey)를 사용하여 세계화의 조류 속에서 나타난 세계 시민으로서의 인식과 탈물질주의 가치관이 공공영역에 대한 신뢰에 어떻게 영향을 미치는지를 분석하였다. Kazakhstan has achieved rapid socio-economic development since her independence from the Soviet Union in 1991, However, the country has still maintained an authoritarian political system. This contradiction allows Kazakhstani to drive conflicting assessment of the performance of public sectors. This paper attempts to explain this conflicting phenomenon in a single theoretical framework, In particular, this paper argues that the emergence of global citizenship caused by the change of institution under the wave of globalization is an important factor that influences the degree of trust of the public sectors. World Value Survey 2014 data are used to analyze the relationship between global citizenship and people’s trust in the public sectors in Kazakhstan. The results show that Kazakhstan"s acquisition of global citizenship has a significant impact on the degree of trust in the public sectors.

나노입자의 군집밀도를 고려한 고분자 나노복합재의 기계적 물성에 대한 멀티스케일 연구

백경민(Kyungmin Baek),신현성(Hyunseong Shin),한진규(Jin-Gyu Han),조맹효(Maenghyo Cho) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12

Interfacial effects which result from interaction between nanoparticles and polymer matrix significantly increase stiffness, thermal conductivity and electrical conductivity of nanocomposites. These effects are known to diminish when interphase of the nanoparticles are percolated. Experimental data from existing researches demonstrated that this phenomenon reduces the mechanical and thermal properties of nanocomposites. In this study, we investigated the effects of nanoparticulate agglomeration on mechanical behavior of nanocomposites by conducting multiscale bridging method in which molecular dynamics (MD) and continuum mechanics are considered. We verify that the mechanical properties of nanocomposites are mainly dependent on volume fraction of free nanoparticles by conducting parametric study about the number of clusters and free particles inside the matrix. Additionally, we find that elastic modulus of nanocomposites influenced by the number of clusters have variances in spite of the same number of agglomerated nanoparticles. We define nanoparticulate agglomeration density to quantify these phenomena with considering various parameters of agglomeration. It is observed that total nanoparticles tend to form single cluster and the mechanical properties of nanocomposites diminish when agglomeration density is sufficiently high.

증강현실 다이어리 [디어리]

백경민(Gyeong Min Baek),김두목(Du Mok Kim),박나현(Na Hyeon Park) 한국HCI학회 2019 한국HCI학회 학술대회 Vol.2019 No.2