• Advances in nano research
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• v.12 no.6
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• pp.593-603
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• 2022

The critical buckling temperature rise of a newly proposed piezoelectrically active sandwich plate (ASP) has been investigated in this work. This structure includes a porous polymeric layer integrated between two piezoelectric nanocomposite layers. The piezoelectric material is made of a passive polymeric material that is activated by lead-free nanowires (NWs) of zinc oxide (ZnO) embedded inside the matrix. In both nanocomposite layers and porous core, functional graded (FG) patterns have been considered for the distributions of ZnO NWs and voids, respectively. By adopting a higher-order theory of plates, the governing equations of thermal buckling are obtained. This set of equations is then treated using an extended mesh-free solution. The effects of plate dimensions, porosity states, and the nanowire parameters have been investigated on the critical buckling temperature rises of the proposed lightweight ASPs with different boundary conditions. The results disclose that the use of porosities in the core and/or mixing ZnO NWs in the face sheets substantially arise the critical buckling temperatures of the newly proposed active sandwich plates.

• Structural Engineering and Mechanics
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• v.82 no.1
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• pp.41-53
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• 2022

We developed an accurate and simple vibration model to calculate the natural frequencies and their corresponding vibration modes for multi-span beam bridges with non-uniform cross-sections. A closed set of characteristic functions of a single-span beam was used to construct the vibration modes of the multi-span bridges, which were considered single-span beams with multiple constraints. To simplify the boundary conditions, the restraints were converted into spring constraints. Then the functional of the total energy has the same form as the penalty method. Compared to the conventional penalty method, the penalty coefficients in the proposed approach can be calculated directly, which can avoid the iteration process and convergence problem. The natural frequencies and corresponding vibration modes were obtained via the minimum total potential energy principle. By using the symmetry of the eigenfunctions or structure, the matrix size can be further reduced, which increases the computational efficiency of the proposed model. The accuracy and efficiency of the proposed approach were validated by the finite element method.

• Applied Microscopy
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• v.50
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• pp.20.1-20.9
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• 2020

Arthropods have an open circulatory system with a simple tubular heart, so it has been estimated that the contractile pumping structure of the cardiac muscle will be less efficient than that of vertebrates. Nevertheless, certain arthropods are known to have far superior properties and characteristics than vertebrates, so we investigated the fine structural features of intercalated discs and cardiac junctions of cardiac muscle cells in the black widow spider Latrodectus mactans. Characteristically, the spider cardiac muscle has typical striated features and represents a functional syncytium that supports multiple connections to adjacent cells by intercalated discs. Histologically, the boundary lamina of each sarcolemma connects to the basement membrane to form an elastic sheath, and the extracellular matrix allows the cells to be anchored to other tissues. Since the intercalated disc is also part of sarcolemma, it contains gap junctions for depolarization and desmosomes that keep the fibers together during cardiac muscle contraction. Furthermore, fascia adherens and macula adherens (desmosomes) were also identified as cell junctions in both sarcolemma and intercalated discs. To enable the coordinated heartbeat of the cardiac muscle, the muscle fibers have neuronal innervations by multiple axons from the motor ganglion.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.138-139
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• 2020

With the rapid progress of industrialization, indoor air quality is a very important factor for modern people who spend most of their day indoors. The recent issue of fine dust and radon on the portal site's popularity search shows that interest in indoor air quality has increased. Fine dust causes respiratory diseases, and radon causes severe lung cancer. The new material was tested using plant activated carbon, palm activated carbon and bamboo activated carbon. Both palm activated carbon and bamboo activated carbon are porous materials and generate smooth physical adsorption. As a result of the experiment, both the activated carbon tends to gradually decrease in strength and fluidity as the replacement ratio increases. The reason for this is that both activated carbons have the property of absorbing moisture, so it is judged that the strength is lowered by absorbing moisture necessary for curing. In the case of fluidity, it is judged that the fluidity is reduced by absorbing the moisture required for the flow. In the future, if the problem of the color of the finished cured body is compensated, it will be possible to manufacture a functional finishing board to replace the existing interior finishing material.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.584-590
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• 2023

In this study, we focus on the recycling of cardboard waste and sugarcane bagasse (SCB) for the preparation of carboxymethyl cellulose (CMC) and its conversion into a biodegradable film. Sodium alginate (SA) was added to form a biodegradable composite film. SA was used to increase film permeability. Glycerol, which is a plasticizer, was used to increase the tensile strength (TS) and film expansion. To characterize the CMC, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy were used. The addition of olive oil to the CMC-SA matrix highlighted its antimicrobial property against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). A slight decrease in tensile strength was observed with the addition of olive oil (OO), which improved the functional properties of the control films as well as lowered moisture content and water solubility. But considering all other factors, the composite films obtained from sugarcane bagasse and cardboard waste incorporated with olive oil are suitable for applications in the field of food packaging.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.894-900
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• 1998

An interphase between carbon fiber and epoxy matrix was introduced to increase impact strength of carbon fiber reinforced composites (CFRC) without sacrificing the interlaminar shear strength. Flexible polymers, I. e., MVEMA (poly(methyl vinyl ether-co-maleic anhydride)) and EMA(poly(ethylene-co-maleic anhydride)), which have reactive functional groups were considered as interphase materials. Weight hain of MVEMA and EMA onto the surface of carbon fibers was evaluated by changing the parameters of electrodeposition process. Electrodeposition mechanism of polymers which have anhydride functional group was identified by IR spectroscopy, that is, the generation of $RCOO^-$ functional group by the attack of hydroxide anion in the basic solution was observed. The weight gain was increased by increasing concentration of polymers, current density, and electrodeposition time. However the excess generation of oxygen gas decreased the weight gain by removing the deposited polymers. Washing in the running water easily removed the deposited polymers which are on the fiber surface without bonding, as a results, only 0.5 wt% of deposited polymers are remained.

• Physical Therapy Korea
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• v.10 no.3
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• pp.17-27
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• 2003

Repetitive transcranial magnetic stimulation (rTMS) modulates cortical excitability beyond the duration of the rTMS trains themselves. Depending on rTMS parameters, a lasting inhibition or facilitation of cortical excitability can be induced. Therefore, rTMS of high or low frequency over motor cortex may change certain aspects of motor learning performance and cortical activation. This study investigated the effect of high and low frequency subthreshold rTMS applied to the motor cortex on motor learning of sequential finger movements and brain activation using functional MRI (fMRI). Three healthy right-handed subjects (mean age 23.3) were enrolled. All subjects were trained with sequences of seven-digit rapid sequential finger movements, 30 minutes per day for 5 consecutive days using their left hand. 10 Hz (high frequency) and 1 Hz (low frequency) trains of rTMS with 80% of resting motor threshold and sham stimulation were applied for each subject during the period of motor learning. rTMS was delivered on the scalp over the right primary motor cortex using a figure-eight shaped coil and a Rapid(R) stimulator with two Booster Modules (Magstim Co. Ltd, UK). Functional MRI (fMRI) was performed on a 3T ISOL Forte scanner before and after training in all subjects (35 slices per one brain volume TR/TE = 3000/30 ms, Flip angle $60^{\circ}$, FOV 220 mm, $64{\times}64$ matrix, slice thickness 4 mm). Response time (RT) and target scores (TS) of sequential finger movements were monitored during the training period and fMRl scanning. All subjects showed decreased RT and increased TS which reflecting learning effects over the training session. The subject who received high frequency rTMS showed better performance in TS and RT than those of the subjects with low frequency or sham stimulation of rTMS. In fMRI, the subject who received high frequency rTMS showed increased activation of primary motor cortex, premotor, and medial cerebellar areas after the motor sequence learning after the training, but the subject with low frequency rTMS showed decreased activation in above areas. High frequency subthreshold rTMS on the motor cortex may facilitate the excitability of motor cortex and improve the performance of motor sequence learning in normal subject.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.04a
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• pp.113-119
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• 2000

The Pansori is a Korean traditional vocal music that has a unique story and melody which converts deep emotion into art. It has both verbal and emotional components. which can be coordinated by large-scale neural network. The purpose of this study is to illustrate the cortical network activated by a Korean traditional opera, Pansori, with different emotional valence using functional MRI (fMRI).Nine right-handed volunteers participated. Their mean age was 25.3 and the mean modified Edinburgh score was +90.1. Activation tasks were designed for the subjects to passively listen to the two parts of Pansories with sad or hilarious emotional valence. White noise was introduced during the control periods. Imaging was conducted on a 1.5T Siemens Vision Vision scanner. Single-shot echoplanar fMRI scans (TR/TE 3840/40 ms, flip angle 90, FOV 220, 64 x 64 matrix, 6mm thickness) were acquired in 20 contiguous slices. Imaging data were motion-corrected, coregistered, normalized, and smoothed using SPM-96 software.Bilateral posterior temporal regions were activated in both of Pansori tasks, but different asymmetry between the tasks was found. The Pansori with sad emotion showed more activation in the light superior temporal regions as well as the right inferior frontal and the orbitofrontal areas than in the right superior temporal regions as well as the right inferior frontal and the orbitofrontal areas than in the left side. In the Pansori with hilarious emotion, there was a remarkable activation in the left hemisphere especially at the posterior temporal and the temporooccipital regions as well as in the left inferior and the prefrontal areas. After subtraction between two tasks, the sad Pansori showed more activation in the right temporoparietal and the orbitofrontal areas, in contrast, the one with hilarious emotion showed more activation in the left temporal and the prefrontal areas. These results suggested that different hemispheric asymmetry and cortical areas are subserved for the processing of different emotional valences carried by the Pansories.

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.137-137
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• 2001

Purpose： The purpose of this study was to identify cerebral cortices related with sexual arousal fro visual sexual stimulation in healthy males using BOLD-based functional MR imaging Method： Sixteen male volunteers with sexually potent(mean age：24) were examined for thi study. Functional MRI was performed on a 1.5T MR scanner(GE Signa Horizon) with birdcage-type head coil. In this study, blood oxygenation level dependent(BOLD) technique was utilized to create fMR image reflecting local brain activities. The BOLD-based fMRI d were obtained from 7 oblique planes using gradient-echo EPI with $90^{\circ}$flip angle, 50ms TE 6000ms TR, $26cm{\times}26$ cm FOV, $128{\times}128$ matrix, and 10mm slice thickness. The sexual stimulation paradigm consisted of two alternating periods of rest and activati and it began with a 1 minute rest, followed by a 2 minute stimulation by a documentary a erotic video film. Brain activation maps were generated by cross-correlation of imag acquired during rest and activation periods. The index of activation was used to compare t number of pixels activated by each task in each volunteer, where the significance of th differences was evaluated by using Students t-test.

• Journal of Applied Biological Chemistry
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• v.62 no.4
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• pp.391-398
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• 2019

The antioxidant, whitening, and anti-wrinkle activity of Spirodela polyrhiza extracts and fractions were evaluated to determine its efficacy as a functional cosmetic material. 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid radical scavenging activities were 44.2 and 74.3%, respectively, at 100 ㎍/mL of SE-E (the ethyl acetate fraction of 70% ethanol extract). To measure anti-wrinkle effects, procollagen biosynthesis and matrix metalloproteinase-1 (MMP-1) inhibition activity were determined. At 25 ㎍/mL of SE (70% ethanol extract), the biosynthesis activity was 48.5%, and SE-E showed the best activity (57.8%) at the same concentration. MMP-1 inhibition activity of SE and SE-E was 13.4 and 28.5%, respectively, at 25 ig/mL. Finally, the inhibition of cellular melanin synthesis and cellular tyrosinase were measured to determine the whitening effect; at 25 ㎍/mL, the inhibition activities of SE were 9.6 and 13.8%, respectively, and those for SE-E were 15.4 and 22.0%, respectively. Our results confirmed the possibility of SE and SE-E as effective functional materials. Further research investigating the antimicrobial, anti-inflammatory, and anticancer activities of S. polyrhiza is necessary to confirm its potential use in the food, cosmetics, and drug industries.