• 한국수소및신에너지학회논문집
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• 제32권1호
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• pp.1-10
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• 2021

Water electrolysis technology, which generates hydrogen using renewable energy resources, has recently attracted great attention. Especially, the polymer electrolyte membrane water electrolysis system has several advantages over other water electrolysis technologies, such as high efficiency, low operating temperature, and optimal operating point. Since research that analyzes performance characteristics using test bench have high cost and long test time, however, model based approach is very important. Therefore, in this study, a system model for water electrolysis dynamics of a polymer electrolyte membrane was developed based on MATLAB/Simulink®. The water electrolysis system developed in this study can take into account the heat and mass transfer characteristics in the cell with the load variation. In particular, the performance of the system according to the stack temperature control can be analyzed and evaluated. As a result, the developed water electrolysis system can analyze water pump dynamics and hydrogen generation according to temperature dynamics by reflecting the dynamics of temperature.

• 한국가시화정보학회지
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• 제20권2호
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• pp.70-77
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• 2022

Skeletal muscle tissues feature cellular heterogeneity, including differentiated myofibers, myoblasts, and satellite cells. Thanks to the presence of undifferentiated myoblasts and satellite cells, skeletal muscle tissues can self-regenerate after injury. In skeletal muscle regeneration, the collective motions among these cell types must play a significant role, but little is known about the dynamic collective behavior during the regeneration. In this study, we constructed in vitro platform to visualize the migration behavior of skeletal muscle cells in specific conditions that mimic the biochemical environment of injured skeletal muscles. We then visualized the spatiotemporal distribution of stresses arising from the differential collectiveness in the cellular clusters under different conditions. From these analyses, we identified that the heterogeneous population of muscle cells exhibited distinct collective migration patterns in the injury-mimicking condition, suggesting selective activation of a specific cell type by the biochemical cues from the injured skeletal muscles.

• 한국전문물리치료학회지
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• 제29권3호
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• pp.194-199
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• 2022

Background: Older adults use different ankle muscle activation patterns during difficult static balance conditions. It has been suggested that this is related to a decline in proprioception with age, resulting in reduced postural balance. However, the association between proprioception and ankle muscle activity during quiet standing has not been directly assessed. Objects: This study aimed to investigate the effects of age and sensory condition on ankle muscle activity and the association between ankle proprioception and ankle muscle activity. Methods: We recruited 10 young women and 9 older women. Ankle proprioception was evaluated using joint position sense (JPS) and force sense (FS) divided by dorsiflexion and plantarflexion. The electromyographic activity of the tibialis anterior (TA) and gastrocnemius (GCM) muscles was collected during quiet standing. Results: Older women activated GCM muscle more than young during quiet standing and when performing difficult tasks. Older women had more errors in JPS dorsiflexion and FS plantarflexion than did young. The GCM muscle activity is related to JPS dorsiflexion and FS plantarflexion. Conclusion: Lower proprioception of the GCM with age leads to increased muscle activity, resulting in reduced postural balance. There was no difference in TA proprioception or muscle activity among older women with frequent physical activity.

• 정보저장시스템학회논문집
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• 제1권1호
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• pp.93-98
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• 2005

Rewritable optical disk is one of the essential data storage media in these days, which takes advantage of the different optical properties in the amorphous and crystalline states of phase change materials. As well known, data transfer rate is one of the most important parameter of the phase change optical disks, which is mostly limited by the crystallization speed of recording media. Therefore, we doped Sn/Bi to $Ge_2Sb_2Te_5$ alloy in order to improve the crystallization speed and investigated the dependence of phase change characteristics on Sn/Bi doping concentration. The Sn/Bi doped $Ge_2Sb_2Te_5$ thin film was deposited by RF magnetron co-sputtering system and phase change characteristics were investigated by X-ray diffraction (XRD), static tester, UV-visible spectrophotometer, electron probe microanalysis (EPMA), inductively coupled plasma mass spectrometer (ICP-MS) and atomic force microscopy (AFM). Optimum doping concentration of Bi and Sn were 5${\~}$6 at.$\%$ and the minimum time for crystallization was below than 20 ns. This improvement is correlated with the simple crystalline structure of Sn/Bi doped $Ge_2Sb_2Te_5$ and the reduced activation barrier arising from Sn/Bi doping. The results indicate that Sn/Bi might play an important role in the transformation kinetics of phase change materials..

• Molecules and Cells
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• 제46권3호
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• pp.153-164
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• 2023

Cancer stem cells (CSCs) are a small population of tumor cells characterized by self-renewal and differentiation capacity. CSCs are currently postulated as the driving force that induces intra-tumor heterogeneity leading to tumor initiation, metastasis, and eventually tumor relapse. Notably, CSCs are inherently resistant to environmental stress, chemotherapy, and radiotherapy due to high levels of antioxidant systems and drug efflux transporters. In this context, a therapeutic strategy targeting the CSC-specific pathway holds a promising cure for cancer. NRF2 (nuclear factor erythroid 2-like 2; NFE2L2) is a master transcription factor that regulates an array of genes involved in the detoxification of reactive oxygen species/electrophiles. Accumulating evidence suggests that persistent NRF2 activation, observed in multiple types of cancer, supports tumor growth, aggressive malignancy, and therapy resistance. Herein, we describe the core properties of CSCs, focusing on treatment resistance, and review the evidence that demonstrates the roles of NRF2 signaling in conferring unique properties of CSCs and the associated signaling pathways.

• 한국운동역학회지
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• 제17권4호
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• pp.115-125
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• 2007

Grould Reaction force(GRF) is important in human movements and GRF measurements are one of the most frequently used tool in biomechanical studies. In the studies of the golf swing motion, people refer to GRF as weight transfer. A successful golf swing motion requires many segments activation sequences which are controled by the nerve system. Due to the inter- and intra-individual variability of the human movement and the movement strategies, reliability of the measurements are important in human movement studies. Previous golf researches were based on group studies and certain events' values were analyzed. The purposes of this study were to determine the number of trials for the reliable golf swing GRF data collection, to reveal the variability level of the meaningful components of the golf swing GRF, and to classify the types of the golf swing GRF patterns. Twenty three male professional golfers($26.4{\pm}6.6$ years, $174.3{\pm}5.2\;cm$, $71.3{\pm}6.5\;kg$) signed an informed consent form prior to participation in this study. GRFs of driver swings were collected with Kistler 9285 force platform and 9865A amplifier, and calculated by the KwonGRF program(Visol, Korea). Sampling frequency was 1080 Hz. GRF data were trimmed from 1.5 s prior to the impact to 0.5 s after the impact. The number of trials for the reliable GRF collection was determined when the change in floating mean overs the 25 % of the standard deviation of that variable. Variabilities of the variables were determined by the coefficient of variation(CV) of 10 %. The types of GRF patterns were determined by visual inspection of the peak GRF shapes. The minimum number of trials for the reliable golf swing GRF data collection was five. Ten-trial seems more conservative. The value of the peak GRF was more reliable than the value of the impact GRF. The CV of the peak GRF and impact GRF were 7.4 %, 15.2 %, respectively. Because of the +/- sigh of the peak GRF appearance time, it was impossible to calculate CV of the peak GRF appearance time. Golf swing GRF patterns were classified as sing peak type, double peak type, and plateau peak type. This classification suggests the presence of the different golf swing weight transfer strategies.

• 한국운동역학회지
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• 제16권1호
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• pp.101-108
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• 2006

The purpose of this study was to compare GRF characteristics during walking wearing jogging and roller shoes. Twelve male middle school students (age: $15.0{\pm}0.0\;yrs$, height: $173.6{\pm}5.0\;cm$, weight: $587.6{\pm}89.3\;N$) who have no known musculoskeletal disorders were recruited as the subjects. Kinematic data from six S-VHS camcorders(Panasonic AG456, 60 fields/s) and GRF data from two force platform; (AMII OR6-5) were collected while subjects walked wearing roller and jogging shoes in random order at a speed of 1.1 m/s. An event sync unit with a bright LED light was used to synchronize the video and GRF recordings. GRF data were filtered using a 20 Hz low pass Butterworth. digital filter and further normalized to the subject's body weight. For each trial being analyzed, five critical instants and four phases were identified from the recording. Temporal parameters, GRFs, displacement of center of pressure (DCP), and loading and decay rates were determined for each trial. For each dependent variable, paired t-test was performed to test if significant difference existed between shoe conditions (p <.05). Vertical GRFs at heel contact increased and braking forces at the end of initial double limb stance reduced significantly when going from jogging shoe to roller shoe condition. Robbins and Waked (1997) reported that balance and vertical GRF are closely related It seems that the ankle and knee joints are locked in an awkward fashion at the heel contact to compensate for the imbalance. The DCP in the antero-posterior direction for the roller shoe condition was significantly less than the corresponding value for the jogging shoe condition. Because the subjects tried to keep their upper body weight in front of the hip to prevent falling backward, the DCP for the roller shoe condition was restricted The results indicate that walking with roller shoes had little effect on temporal parameters, and loading and decay rates. It seems that there are differences in GRF characteristics between roller shoe and jogging shoe conditions. The differences in GRF pattern may be caused primarily by the altered position of ankle, knee, and center of mass throughout the walking cycle. Future studies should examine muscle activation patterns and joint kinematics during walking with roller shoes.

• 한국운동역학회지
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• 제24권2호
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• pp.173-180
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• 2014

The purpose of this study was to investigate the effect of combined exercise on injury risk factors of lower extremity during landing. Ten sports talented athletes participated in this study. Sports talented athletes participated in a combined exercise (sports talented exercise, coordination) for 16 weeks. A three-dimensional motion analysis was performed using eight infrared cameras (sampling rate of 100 Hz), one force plate, and electromyography system (sampling rate of 1000 Hz) during landing. Kinetic, and kinematics analysis including average impulsive force, angle of lower extremity, vertical stiffness, onset of muscle activation were calculated by Matlab2009a software. Paired t-test was performed at alpha=.05. The average impulsive force in landing phase was not statistically significant (t=-.748, p=.474). The hip joint angle was more decreased in post test compared to pre test (E1: t=2.682, p=.025, E2: t=5.609, p=.000, E3: t=2.538, p=.032). The knee joint (E1: t=-.343, p=.739, E2: t=1.319, p=.220, E3: t=.589, p=.570) and ankle joint (E1: t=.081, p=.937, E2: t=.784, p=.453, E3: t=.392, p=.704) angle were tended to decrease after combined exercise. The vertical stiffness was tended to decrease after combined exercise (t=1.972, p=.080). Onset of quadriceps femoris (t=.698, p=.503) and medial gastocnemius (t=1.858, p=.096) were tended to be faster than biceps femoris (t=-.333, p=.747) after combined exercise. Although thses findings were not statistically significant except on a hip joint angle, risk factors of lower extremity such as joint angle, vertical stiffness and onset of quadriceps femoris, medial gastrocnemius were positively changed after the combined exercise but an additional training for improved onset of biceps femoris would be required in the future.

• 대한약리학회지
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• 제13권2호
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• pp.1-9
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• 1977

최근 강심작용 약물로 보고된 부자 부타놀 분획의 가토 심방근에서의 자극빈도에 따른 강심효과를 분석한 결과는 다음과 같다. 1) 가토 심방근의 수축력은 자극빈도에 따라 polyphasic한 수축양상을 보였으며 rested-state contraction은 $120{\sim}400sec$의 interval에서 나타났으며 이후 10sec의 간격까지는 급격한 수축력의 감소를 보이는, 축적NIEA가 PIEA의 양을 능가하는 양상을 보였으며 이 이하의 자극 빈도에서는 수축력의 증가를 보였고 대부분 0.25 sec이하의 빈도의 자극으로는 수축력의 감소를 보였다. 2) Ouabain은 저 농도에서는 interval-strength curve에 대하여 rested-state contraction의 증가와 전 자극빈도에서 비슷한 수축력의 증가를 나타내었으며, 고농도에서는 rested-state contraction의 증가와 축적 NIEA의 소멸 속도를 증가시켰으나 이는 rested-state contraction을 나타내는 시간의 단축에 따른 이차적 효과로 판정하였다. 또한 ouabain 자극빈도에 따른 강심 효과의 양상은 세포외 calcium 농도를 증가시킨 때와 유사한 양상이었다. 3) Norepinerhrine은, rested-state contraction에는 거의 영향을 주지 않았으며, 고 빈도에서 더욱 현저한 강심 작용을 나타내었고 축적 PIEA의 양의 증가와 매 beat 당 산출하는 PIEA의 양의 증가를 나타내었다. 4) 부자 부타놀 분획은 norepinephrine과 유사하고 빈도에서 수축력의 증가가 현저 하였으며, 수축력의 증가는 용량 반응 상관을 보였으며, PIEA 축적량 및 매 beat 당 산출하는 PIEA를 증가 시켰다. 따라서 고빈도에서의 강력한 수축력의 증가는 PIEA에 대한 효과에 의할 것으로 사료하였다.

• 벤처창업연구
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• 제12권1호
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• pp.61-71
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• 2017

지역축제란 지역기반창업기업들에게 매우 소중한 홍보 및 판매의 장이 될 수 있다. 그렇다면 지역축제의 서비스품질은 이들의 제품 판매 활성화에 직접적으로 기여할 수 있는가? 기존의 축제서비스품질과 관련된 연구에서는 축제서비스 품질의 관광산업적 성과에 주로 초점을 맞추었던 것과는 달리, 우리는 축제서비스 품질이 제품판매에 미치는 영향에 초점을 맞추어 연구를 진행하였다. 선행연구 분석을 토대로 하여 우리는 "지역축제의 서비스품질은 지역이미지를 매개로 지역기반창업기업의 제품에 대한 소비자의 구매의도에 영향을 줄 것이다"라는 가설을 세우고 연구를 진행하였다. 그 결과 첫째, 축제서비스 품질은 구매의도에 직접적으로 영향을 주지 않았다. 공감성 차원을 제외할 땐 다른 차원은 모두 직접적 영향을 주지 않았다. 반면 축제서비스 품질의 각 차원은 확신성을 제외하고 지역 이미지를 매개로 구매의도에 유의미한 영향을 주었다. 그리고 구매의도는 구매행동에도 실질적으로 큰 영향을 미치고 있었다. 이를 통해 우리는 지역축제서비스품질은 지역이미지를 매개로 할 때, 지역기반창업기업의 제품판매에 영향을 미친다는 점을 확인할 수 있었다. 다만 영향은 직접적인 영향이 아니라 간접적인 영향이었다. 또한 지역이미지가 중요한 영향을 미치므로 지역이미지를 개선하기 위한 노력이 선행되어야 한다는 점을 제언할 수 있다. 더하여 지역축제서비스 품질의 향상은 지역기반창업기업제품 판매에 긍정적 영향을 준다는 점을 확인할 수 있었으며, 특히 공감성 차원이 영향을 많이 준다는 점을 또한 확인할 수 있었다.