(A) Study on FMT/OFDM Systems for Wireless Communications

Maste

Reversibly Thermochromic Cyclic Dipeptide Nanotubes

Owing to their capability of forming extensive hydrogen bondings and the facile introduction of chirality, cyclic dipeptides (CDPs) have gained great attention as scaffolds for functional supramolecules. Surprisingly, introduction of a photopolymerizable diacetylene (DA) moiety to the CDP afforded nanotubular structures with enhanced stability and reversible thermochromism. A series of CDP-containing DAs (CDP-DAs) are prepared by coupling 10,12-pentacosadiynoic acid with CDPs, cyclo(-Gly-Ser) and cis/trans cyclo(-Ser-Ser). Fabrication of CDP-DA self-assemblies in a polar chloroform and methanol solvent mixture affords nanotubes comprising single-wall and multiwall structures. The self-assembly behavior and morphology characteristic are examined by scanning electron microscopy and transmission electron microscopy. Next, X-ray diffraction analysis confirms well-ordered lamellar structures with a perfect agreement with the bilayer formation leading to the tubular structure via lamellar scrolling behavior. Upon UV irradiation, monomeric CDP-DA tubular assemblies result in the blue-colored CDP/polydiacetylene (PDA) nanotubes. Interestingly, CDP/PDA nanotubes exhibit a reversible blue-to-red change for over 10 consecutive thermal cycles. The CDP-DA/PDA supramolecular system demonstrates potential applications in developing stimulus-responsive functional materials.This investigation was supported financially by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (NRF-2017R1A2A1A05000752, 2012R1A6A1029029)

Topochemical polymerization of macrocyclic diacetylene with a naphthalene moiety for a tubular-shaped polydiacetylene chromophore

Tubular-shaped chromophores have great potential in chemical and material sciences. A naphthalene-containing macrocyclic diacetylene (MCDA-Naph) was synthesized to access covalently linked organic nanotubes (ONTs) through topochemical polymerization. Single crystal X-ray analysis revealed that MCDA-Naph adopts the desired tubular array with favorable molecular orientation. UV irradiation of the molecularly stacked MCDA-Naph resulted in 1,4-addition polymerization and the generation of conjugated ene-yne chromophores. Density functional theory (DFT) provided evidence for tubular polydiacetylene nanotubes.This study was supported by the Samsung Research Funding Center of Samsung Electronics (Project Number SRFC-MA1501-06) and the National Research Foundation of Korea (NRF-2017R1A2A1A05000752)

Reinforced PEI/PVdF Multicore-Shell Structure Composite Membranes by Phase Prediction on a Ternary Solution

To construct a polyetherimide (PEI)-reinforced polyvinylidene fluoride (PVdF) composite membrane with multicore-shell structure, a ternary solution was prepared and electrospun by single-nozzle electrospinning. A theoretical prediction was made for the feasibility of complete distinction of two phases. The diameters of the membrane fibers and the PEI multi-core fibrils varied with the PEI ratio and the spinning time, respectively. The tensile strength and modulus were improved to 48 MPa and 1.5 GPa, respectively. The shrinkage of the membrane was only 6.6% at 180 degrees C, at which temperature the commercial PE separator melted down. The reinforcement in mechanical and thermal properties is associated with multiple PEI nanofibrils oriented along the fiber axis. Indeed, the unique morphology of self-assembled multicore-shell fibers plays an important role in their properties. All in all, PEI/PVdF membranes are appropriate for a lithium-ion battery application due to their high mechanical strength, excellent thermal stability, and controllable textural properties.This work was supported by a grant from the Korea Institute of Science and Technology (KIST) Institutional program (2Z05360, 2E28020, 2Z05400) and the Industrial Core Technology Development Program (10052760) funded by the Ministry of Trade, Industry and Energy, Korea

제어 체적 유한요소법(CVFEM)을 이용한 이형 압출 다이 내의 삼차원 유동해석

Thesis (master`s)--서울대학교 대학원 :재료공학부,2001.Maste

(A)Study on wafer-level packaged single crystalline silicon single-pole nine-throw RF MEMS switch

학위논문(박사)--서울대학교 대학원 :전기·컴퓨터공학부,2007.Docto

SiOG 기판을 이용한 단결정 실리콘 RF MEMS 스위치의 제작 및 특성에 관한 연구

학위논문(석사)--서울대학교 대학원 :전기·컴퓨터공학부,2004.Maste

(A) study on the effects of weight-transfer training upon the gait paterns of hemiplegic patients through visual and auditory feedback

보건학과/석사[한글] 이 연구의 목적은 Limb Load Monitor의 시각 및 청각 되먹임을 이용한 체중이동 훈련이 편마비 환자들의 체중부하 분포와 보행특성에 미치는 효과를 알아보는데 있다. 연구대상은 1995년 1월 5일부터 3월 15일까지 연세대학교 의과대학 재활병원에 입원중이거나 통원 재활치료를 받고 있는 편마비 환자 18명을 대상으로 체중부하 및 균형훈련기기인 Limb Load Monitor로 훈련 후 훈련 전과 후의시간경과에 따른 체중부하의 변화를 알아보았고, 보행특성의 변화는 ink foot print를 이용하여 훈련 전과 후 각각 측정하여 비교하였다. 사용된 분석방법은 반복 측정된 1 요인 분산분석과 짝비교 t 검정이었다. 결과는 다음과 같다. 1. 연구 대상자 18명이 환측 하지(38.4%)보다 건측 하지(61.6%)에 체중부하를 더 많이 하고 있었다. 2. 환측 하지의 체중부하율은 훈련 전에 평균 38.4%에서 훈련 직후 46.0%, 30초후 45.7%, 60초후 45.3%로 통계학적으로 유의하게 증가하였다. 3. 훈련 전과 후의 보행특성은 훈련 후에 보행 속도가 3.65 cm/sec 빨라졌으며, 환측 하지의 보폭은 5.37cm, 건측 하지의 보폭은 4.77cm로 길어 졌고, 체중지지면이 1.19cm 좁아져 통계학적으로 유의한 차이를 보였다. 이상의 결과로 미루어 볼때 Limb Load Monitor의 시각 및 청각 되먹임을 이용한 체중이동 훈련이 편마비 환자의 대칭적인 서기자세의 향상에 도움을 주고, 보행특성을 개선하는 것으로 나타났다. [영문] The objective of this study was to identify the effects of weight-transfer training on the weight bearing distribution and gait patterns of hemiplegic patients through visual and auditory feedback using a limb load monitor. The subjects of this study were 18 hemiplegic patients who had been hospitalized or were visited out-patient department of the Rehabilitation Hospital, College of Medicine, Yonsei University, from January 5, 1995 through March 15, 1995. Pre- and post- training changes in gait patterns were measured using ink foot prints as well as by recording weight bearing distribution using a limb load monitor. The data were analyzed by the repeated measure one way ANOVA and paired t-test. The finding were as follows: 1. Prior to the training, 18 subjects bore more weight on the sound leg(61.6%) than on the affected leg(38.4%). 2. Posterior to the training, the average percentage of weight bearing on the affected leg increased significantly from 38.4% prior to training; to 46.0% immediately after training; 45.7% after a 30 second delay; and 45.3% after a 60 second. 3. The difference in gait patterns between pre- and post- training was statistically significant, with an increase in gait velocity to 3.65 cm/sec post-training; an increase in stride length to 5.37 cm on the affected side; 4.77 cm on the sound side; and a narrowing of the base of support to 1.19 cm. In conclusion, hemipiegic weight-transfer training using visual and auditory feedback with a limb load monitor was found to be enhancing symmetrical standing posture, and simultaneously improve gait patterns.restrictio