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Choi, Joonhyeong,Kim, Wansun,Kim, Donguk,Kim, Seonha,Chae, Junsu,Choi, Siyoung Q.,Kim, Felix Sunjoo,Kim, Taek-Soo,Kim, Bumjoon J. American Chemical Society 2019 Chemistry of materials Vol.31 No.9
<P>Mechanical properties of conducting polymers are an essential consideration in the design of flexible and stretchable electronics, but the guidelines for the material design having both high mechanical and electrical properties remain limited. Here we provide an important guideline for the design of mechanically robust, electroactive polymer thin films in terms of the molecular weight of the polymers. These studies based on a highly efficient, representative n-type conjugated polymer (P(NDI2OD-T2)) revealed a marked enhancement in mechanical properties across a narrow molecular weight range, highlighting the existence of a critical molecular weight that can be exploited to engineer films that balance processability and mechanical and electronic properties. We found the thin films formed from high molecular weight polymers (i.e., number-average molecular weight (<I>M</I><SUB>n</SUB>) ∼ 163 kg mol<SUP>-1</SUP>) to exhibit superior mechanical compliance and robustness, with a 114-fold enhanced strain at fracture and a 2820-fold enhanced toughness, as compared to those of low molecular weight polymer films (<I>M</I><SUB>n</SUB> = 15 kg mol<SUP>-1</SUP>). In particular, we observed a jump in the mechanical properties between the <I>M</I><SUB>n</SUB> = 48 and 103 kg mol<SUP><B>-</B>1</SUP>, yielding a 26-fold enhanced strain at fracture and a 160-fold enhanced toughness. The significant improvement of tensile properties indicates the presence of a critical molecular weight at which entangled polymer networks start to form, as supported by the analysis of the thermal and crystalline properties, specific viscosity, and microstructure. Our work provides useful guidelines for the design of conjugated polymers with recommendations for the best combinations of mechanical robustness and electrical performance for flexible and stretchable electronics.</P> [FIG OMISSION]</BR>
하우스재배에서 수확시기에 따른 녹차의 화학적 성분 변화
이선하(Seonha-Lee),최갑성(Kap Seong-Choi),최정(Jeong-Choi) 한국차학회 2004 한국차학회지 Vol.10 No.1
Chemical components of the leaves of 6 tea varieties cultivated in a greenhouse were studied to see the effect of plucking season on chemical components. The amounts of total nitrogen, amino acids, theanine, caffeine, catechins, vitamin C and ash were analyzed using NIR(Near Infrared Spectroscopy) system. Tea leaves cultivated in greenhouse contained 3.87-6.40% total nitrogen. 0.95-4.56% free amino acids, 0.68-2.65% theanine, 2.16-3.92% caffeine, 9.55-15.5% catechins, 32.1-318.3 mg% vitamin C and 11.01-23.05% ash on dry weight basis. The amount of the components except ash in the greenhouse cultivated tea leaves were higher than those in the field. The first crop contained more total nitrogens, free amino acids, theanine and caffeine, and contained less vitamin C and ash than the second and the third crops. Korean wild tea plants had more caffeine and catechins, and less free amino acids and theanine than the Japanese varieties. The old leaves contained less free amino acids, theanine, caffeine and catechins than the new leaves.
REMARKS ON NONSPECIAL LINE BUNDLES ON GENERAL κ-GONAL CURVES
CHOI, YOUNGOOK,KIM, SEONJA Korean Mathematical Society 2015 대한수학회지 Vol.52 No.5
In this work we obtain conditions for nonspecial line bundles on general ${\kappa}$-gonal curves failing to be normally generated. Let L be a nonspecial very ample line bundle on a general ${\kappa}$-gonal curve X with ${\kappa}{\geq}4$ and $deg\mathcal{L}{\geq}{\frac{3}{2}}g+{\frac{g-2}{{\kappa}}}+1$. If L fails to be normally generated, then L is isomorphic to $\mathcal{K}_X-(ng^1_{\kappa}+B)+R$ for some $n{\geq}1$, B and R satisfying (1) $h^0(R)=h^0(B)=1$, (2) $n+3{\leq}degR{\leq}2n+2$, (3) $deg(R{\cap}F){\leq}1$ for any $F{\in}g^1_k $. Its converse also holds under some additional restrictions. As a corollary, a very ample line bundle $\mathcal{L}{\simeq}\mathcal{K}_X-g^0_d+{\xi}^0_e$ is normally generated if $g^0_d{\in}X^{(d)}$ and ${\xi}^0_e{\in}X^{(e)}$ satisfy $d{\leq}{\frac{g}{2}}-{\frac{g-2}{\kappa}}-3$, supp$(g^0_d{\cap}{\xi}^0_e)={\phi}$ and deg$(g^0_d{\cap}F){\leq}{\kappa}-2$ for any $F{\in}g^1_k$.
지역아동센터 종사자의 직무스트레스가 직무만족에 미치는 영향 -직무열의의 매개효과-
박선태 ( Seontae Park ),최용민 ( Yongmin Choi ),원유나 ( Youna Weon ) 아시아문화학술원 2018 인문사회 21 Vol.9 No.5
본 연구는 지역아동센터 종사자들이 지각하는 직무스트레스가 직무만족에 미치는 영향력과 직무열의의 매개효과를 검정하고자 하였다. 연구방법은 확인적 요인분석, 상관관계분석, 구조방정식 모형 분석을 사용하였다. 결과를 요약하면, 첫째, 직무스트레스가 높을수록 직무만족도가 낮아지는 것으로 나타났다. 둘째, 직무스트레스가 많을수록 직무열의는 낮아지는 것으로 나타났다. 셋째, 직무열의에서 직무만족에 이르는 경로는 직접효과로만 구성되어 있으며 직무열의는 직무만족에 긍정적인 영향으로 분석되어, 직무열의는 직무스트레스를 완화하여 직무만족을 높이는 부분매개 역할을 하는 것으로 분석되었다. 연구의 실천적 시사점은 첫째, 지역아동센터 종사자들이 직무스트레스를 줄이고 직무열의를 높일 수 있는 환경을 개선하기 위한 지지적 체계에 대한 사회적, 정책적 관심이 필요하다. 둘째, 지역아동센터 종사자들의 직무스트레스는 직무만족에 부정적인 영향을 미치고 있으며, 종사자들이 직무스트레스를 관리할 수 있는 힐링문화센터 등 정책적 지원시스템이 필요하다. 지역아동센터 종사자들의 직무열의는 직무만족을 높여주고 결국, 지역아동센터 아동들의 삶의 질을 높일 수 있을 것이다. The purpose of this study was to examine the effect of job stress perceived by local child care workers on job satisfaction and the mediating effect of job enthusiasm. The research method used confirmatory factor analysis, correlation analysis, and structural equation model analysis. First, the higher the job stress, the lower the job satisfaction. Second, the more job stress, the lower the job enthusiasm. Third, the path from job enthusiasm to job satisfaction consisted only of direct effect. Job enthusiasm was analyzed as having a positive effect on job satisfaction, and job enthusiasm was analyzed as a partial mediation to improve job satisfaction by alleviating job stress. The practical implications of this study are as follows: First, social and policy attention should be paid to the supportive system to improve the environment in which the local child center workers reduce job stress and job enthusiasm. Second, job stress of local child care center workers has a negative effect on job satisfaction, and a policy support system such as Healing Cultural Center where workers can manage job stress is needed. Job enthusiasm of local child care workers will increase job satisfaction and eventually improve the quality of life of children in local child care centers.
김선재(Seonjae Kim),최경환(Kyunghwan Choi) 육군사관학교 화랑대연구소 2021 한국군사학논집 Vol.77 No.3
Blockchain has currently proven to be a representative technology of cryptocurrency such as Bitcoin and Ethereum. In addition, its application in various fields of society such as economy, logistics, and services, and services are already being applied to public institution domestic, foreign companies. In line with this technological trend, blockchain technology is actively being applied to the defense sector. To satisfy this trend the Ministry of National Defense is pushing for smart defense innovation to apply the 4th Industrial Revolution technology to the defense sector. In the Military, facility work goes beyond the meaning of the building and has the characteristics. professional design should be carried out in consideration of wartime and peacetime operational planning and auxiliary duties to show the best combat power. Therefore, plans and initiatives for military facilities must be systematically implemented, and efficient maintenance measures and long-term plans are needed. In this study, we would like to present a plan that can contribute a lot to the construction and maintenance of modernized and advanced defense and military facilities through the integration of military facility work and blockchain technology.