• Journal of Acupuncture Research
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• v.21 no.6
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• pp.177-186
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• 2004

Introduction : Recent studies Suggested that there is a strong correlation between acupuncture stimulation and its related cortical activation. Anther study showed that either positive or negative BOLD effects could be observed depending on anatomical structure in acupuncture stimulation. In ttis study, we investigated a new acupoint $KI_6$ (照海), which was known as motor-related acupoint and obtained an evidence that the stimulation of $KI_6$ resulted in either negative or positive BOLD response to stimulation. Methods & Results : 1. Subjects and paradigms : Two separate stimulation paradigms were performed on five healthy (aged 22-23 yrs) in this study. First, the paradigm of acupuncture stimulation was that the acupuncture needle was inserted in acupoints $KI_6$, which is located in lateral side of the foot and then continuously twisted(補瀉를 除外한 捻轉法) for 70 seconds for 10 cycles of activation. During rest period (70 seconds), the needle was completed removed from acupoint. Total 60 cycles were performed and 10 images were obtained per cycle. Second, nonacupoint was randomly selected and the same paradigm was performed as acupoint stimulation. The stimulation protocol comprised 10 cycles of alternating. activation and rest (10 images per cycle). Total 60 cycles were performed and each cycle take about 1.5 sec for motor task. Subjects take an at least 15 minutes break before starting anther paradigm. 2. fMRI mapping : Multi-slice functional images were obtained on a 1.5T Magnetom Vision MRI scanner (Simens Medical, Erlangen, Germany) equipped with high performance whole-body gradients. The BOLD T2 * - weighted images were acquired with acho planar imaging sequence (TR = 1.2 sec, TE = 60 msec, and flip angle = $90_{\circ}$). The other sequence parameter are : FOV = 210 mm, matrix=$64{\times}128$ or $64{\times}64$, slice number=10 and slice thickness = 5 or 8 mm. the anatomic images were obtained with Spin-echo T1-weighted images. The resulting images were then anaiyzed with STIMULATE (CMRR, U. of Minnesota) to generate functional maps using a student T-test (p < 0.005) and cluster analysis. Both positive and negative response were evaluated. Conclusions : We have observed the activation of the motor cortex by stimulating motor-related acupoint ($KI_6$). Among five subjects, negative BOLD response was shown in four and positive response in one. All subjects showed positive response to conventional finger flexion-extension task. To understand the detailed mechanisms of correlation between acupuncture stimulation and BOLD fMRI changes and two typs of response, further study strongly required.

• Journal of Periodontal and Implant Science
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• v.34 no.3
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• pp.543-549
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• 2004

Chitosan has been widely researched as bone substitution materials and membranes in orthopedic/periodontal applications. Chitosan nanofiber membrane was fabricated by chitosan nanofiber using electrospinning technique. The structure of the membrane is nonwoven, three-dimensional, porous, and nanoscale fiber-based matrix. The aim of this study was to evaluate the biocompatibility of chitosan nanofiber membrane and to evaluate its capacity of bone regeneration in rabbit calvarial defect. Ten mm diameter round cranial defects were made and covered by 2 kinds of membranes (Gore-Tex membrane, chitosan nanofiber membrane) in rabbits. Animals were sacrificed at 4 weeks after surgery. Decalcified specimens were prepared and observed by microscope. Chitosan nanofiber membrane maintained its shape and space at 4 weeks. No inflammatory cells were seen on the surface of the membrane. In calvarial defects, new bone bridges were formed at all defect areas and fused to original old bone. No distortion and resorption was observed in the grafted chitosan nanofiber membrane. However bone bridge formation and new bone formation at the center of the defect could not be seen in Gore-Tex membranes. It is concluded that the novel membrane made of chitosan nanofiber by electrospinning technique may be used as a possible tool for guided bone regeneration.

• Journal of The Korean Association For Science Education
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• v.18 no.4
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• pp.527-537
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• 1998

This article is a part of a research on the elementary science curriculum development to enhance creative problem-solving abilities. The components of the curriculum have been identified as 'scientific knowledge', 'process skills' & 'divergent/critical thinking'. Among these components, construction of the scientific knowledge that enables creative problem-solving abilities has been selected as an intensive research topic for the purpose of the present research. To avoid or to prevent the knowledge learned from separate facts and concepts, five themes have been selected so as to incorporate with all three areas of the elementary science curriculum, i.e., physical science, earth science and life science. The five themes are, 'structure', 'change', 'interaction', 'energy' and 'stability'. The contents of elementary science, which have been selected from the 3rd, 6th and 7th National Elementary Science curriculum, were reconstructed based on the five themes given above. The results of reconstruction are presented in the form of matrix, such that the vertical axis represents how the concepts are related within each domain of science, while the horizontal axis shows how the concepts are interconnected between domains of science. Therefore, based upon the five themes, individual or separate knowledge can be put into more unified knowledge so that contribution of knowledge transfer to new ones can be expected for leaners who will be creative in problem-solving. The process and products of the curriculum development as well as the background of the present research are described and discussed in detail.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.282-288
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• 2015

A new energetic thermoplastic elastomer based on the azidated polybutadiene(Az-PBD)/ethylene vinyl acetate copolymer (EVA) blends was prepared, and structure and properties of the blends were invetigated by SEM, DSC, DMA, tensile testing and combustion test. The Az-PBD was synthesized via a two-step process involving the addition reaction of commercially available 1,2-PBD with $Br_2$ and subsequent nucleophilic substitution reaction of the brominated PBD with $NaN_3$. EVA/Az-PBD with 90/10, 80/20, 70/30 (wt/wt) was prepared by a solution blending. SEM, DSC, and DMA results revealed that the blends are partially compatible and Az-PBD is dispersed in continuous EVA matrix. Tensile test showed that modulus and tension set increased while elongation-at-break of the blends decreased with increasing Az-PBD content in the blends, but all the blends showed a elongation at break as high as 700% and a tension set of less than 5%, indicating that the blends are typically elastomeric. Combustion test showed that, with increasing Az-PBD content in the blend, higher energy can be released.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.4
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• pp.239-245
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• 2014

Finite element modeling of composite structures may be cumbersome due to complex distributions of reinforcements. In this paper, an efficient scheme is proposed that can generate periodic meshes for the composite structures. Regular meshes with hexahedral finite elements are first prepared, and the elements are then trimmed to fit external surfaces of reinforcements in the composite structures. The trimmed hexahedral finite elements located at interfaces between the matrix and the reinforcements correspond to polyhedral finite elements, which allow an arbitrary number of nodes and faces in the elements. Because the trimming process is consistently conducted by means of consistent algorithms, the elements of the reinforcements are automatically compatible with those of the matrices. With the additional consideration of periodicity of reinforcements in a representative volume element(RVE), the proposed scheme provides periodic meshes in an efficient manner, which are compatible for each pair of periodic boundaries of the RVE. Therefore, periodic boundary conditions for the RVE are enforced straightforwardly. Numerical examples demonstrate the effectiveness of the proposed scheme for finite element modeling of complex composite structures.

• Journal of Gifted/Talented Education
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• v.25 no.5
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• pp.673-696
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• 2015

Students' perception of science-related career strongly influences the formation of career motivation in science. Especially, the high level of science gifted students' positive perceptions plays an important role in allowing them to continue to study science. This study compared perceptions of science-related career between general and gifted middle school students using semantic network analysis. To ensure this end, we first structuralize semantic networks of science-related careers that students perceived. Then, we identified the characters of networks that two different student groups showed based on the structure matrix indices of semantic network analysis. The findings illustrated that the number of science-related careers shown in science gifted students' answer is more than in general students' answer. In addition, the science gifted students perceived more diverse science-related careers than general students. Second, scientific career such as natural scientists and professors were shown in the core of science gifted students' perception network whereas non-research oriented careers such as science teachers and doctors were shown in the core of general students' perception network. In this study, we identified the science gifted students' perceptions of science-related career was significantly different from the general students'. The findings of current study can be used for the science teachers to advise science gifted students on science-related careers.

• Membrane Journal
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• v.19 no.4
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• pp.341-347
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• 2009

Nanohybrid based on environmentally friendly and biodegradable polymer, poly propylene carbonate (PPC) and cloisite 20B (PPC/C-20B) have been synthesized by solution blending method and their morphology, thermal and water absorption properties have been evaluated. The structure of PPC/C-20B nanohybrid was confirmed by X-ray diffraction (XRD). The thermal property of PPC and PPC/C-20B nanohybrid were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetric (DSC). The experimental results demonstrated that nanohybrid showed the highest thermal stability in TGA and DSC. TGA tests revealed that the thermal decomposition temperature ($T_{d50%}$) of the nanohybrid increased significantly, being $23^{\circ}C$ higher than that of pure PPC while DSC measurements indicated that the introduction of 5 mass% of clay increased the glass transition temperature from 21 to $30^{\circ}C$. Further the water absorption capacity of the PPC was significantly decreased by the incorporation of clay. Water absorption cause degradation of the coating by the moistures and affect the physical and mechanical performance. This result indicates that organic modifiers have effect on thermal and water absorption capacity of PPC and are of importance for the practical process and application of PPC.

• Polymer(Korea)
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• v.26 no.5
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• pp.644-652
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• 2002

This study aims at developing the conductive pastes consisting of room temperature vulcanizing (RTV) silicone and metal powder as matrix and filler, respectively. Electrical and rheological properties of metal - filled polymer composites are in general strongly affected by particle shape, side and dispersion state of the filler. In highly filled systems, particles tend to form very complex agglomerated structure which is easily changed when subjected to shear deformation. And the breakdown of agglomerated particles due to shear usually leads to the change of electrical conductivity of the composite. In this study, the effect of particle size and dispersion state of filler on the electrical conductivity of the composites are investigated to offer the selection criteria of conductive filler by measuring the rheological properties of uncured composites and the electrical conductivity of the cured composites. It was found that the type of metal filler systematically affected the rheological property, the susceptibility to shear and the degree of change of electrical conductivity of the composite. The effect of shear on the properties is more conspicuous in the composites containing large particle, indicating that both rheological and electrical properties can be improved by controlling the dispersion state at a given filler content.

• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.111-116
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• 1998

Thirteen InGaAs/InGaAsP separate-confinement heterostructure multiple quantum well lasers were designed such that the strain in the active layer from 0.9% compressive strain to 1.4% tensile, and their threshold current density was caluculated to see the effects of strain on the threshold current density. The well width was adjusted such that the bandgap of the quantum well is 1.55 ${\mu}{\textrm}{m}$, For the calculation of the band structure and transition matrix element needed for the gain calculation, a block diagonalized 8$\times$8 second-order $\to{k}.\to{p}$ Hamiltonian was used to incorporate the conduction band nonparabolicity and the valence band mixing. The threshold current density shows discontinuity at 0.4% tensile strain where the first heavy-hole subband and the first light-hole subband cross and at 0.5% tensile strain where the second conduction subband begins to exist. The threshold current density at room temperature has a maximum around these 0.4-0.5% tensile strains, and as strain varies in either direction it decreases first and then increases a little after a local minimum. This calculated trend is consistent with the other reported experimental results. We discussed the results of this calculation in comparison with other theoretical or experimental papers on the effect of strain.

• Archives of Plastic Surgery
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• v.36 no.5
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• pp.578-582
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• 2009

Purpose: In extensive deep burn of the lower limb, due to less amount of soft tissue, bone is easily exposed. When it happens, natural healing or reconstruction with skin graft only is not easy. Local flap is difficult to success, because adjacent skins are burnt or skin grafted tissues. Muscle flap or free flap are also limited and has high failure rate due to deep tissue damage. The authors acquired good outcome by performing one - stage operation on bone exposed soft tissue defect with AlloDerm$^{(R)}$(LifeCell, USA), an acellular dermal matrix producted from cadaveric skin. Methods: We studied 14 bone exposed soft tissue defect patients from March 2002 to March 2009. Average age, sex, cause of burn, location of wound, duration of admission period, and postoperative complications were studied. We removed bony cortex with burring, until conforming pinpoint bone bleeding. Then rehydrated AlloDerm$^{(R)}$(25 / 1000 inches, meshed type) was applicated on wound, and thin split thickness(6 ~ 8 / 1000 inches) skin graft was done at the immediately same operative time. Results: Average age of patients was 53.6 years(25 years ~ 80 years, SD = 16.8), and 13 patients were male(male : female = 13 : 1). Flame burn was the largest number. (Flame burn 6, electric burn 3, contact burn 4, and scalding burn 1). Tibia(8) was the most affected site. (tibia 8, toe 4, malleolus 1, and metatarsal bone 1). Thin STSC with AlloDerm$^{(R)}$ took without additional surgery in 12 of 14 patients. Partial graft loss was shown on four cases. Two cases were small in size under $1{\times}1cm$, easily healed with simple dressing, and other two cases needed additional surgery. But in case of additional surgery, granulation tissue has easily formed, and simple patch graft on AlloDerm$^{(R)}$ was enough. Average duration of admission period of patients without additional surgery was 15 days(13 ~ 19 days). Conclusion: AlloDerm$^{(R)}$ and thin split thickness skin graft give us an advantage in short surgery time and less limitations in donor site than flap surgery. Postoperative scar is less than in conventional skin graft because of more firm restoration of dermal structure with AlloDerm$^{(R)}$. We propose that AlloDerm$^{(R)}$ and thin split thickness skin graft could be a solution to bone exposured soft tissue defects in extensive deep burned patients on lower extremities, especially when adjacent tissue cannot be used for flap due to extensive burn.