• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.3
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• pp.332-336
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• 2024

High-energy bandgap material silicon carbide (SiC) is gaining attention as a next-generation power semiconductor material, and in particular, SiC-based MOSFETs are developed as representative power semiconductors to increase the breakdown voltage (BV) of conventional planar structures. However, as the size of SJ (Super Junction) MOSFET devices decreases and the depth of pillars increases, it becomes challenging to uniformly form the doping concentration of pillars. Therefore, a structure with different doping concentrations segmented within the pillar is being researched. Using Silvaco TCAD simulation, a SJ VVD (vertical variation doping profile) MOSFET with three different doping concentrations in the pillar was studied. Simulations were conducted for the width of the pillar and the doping concentration of N-epi, revealing that as the width of the pillar increases, the depletion region widens, leading to an increase in on-specific resistance (R_on,sp) and breakdown voltage (BV). Additionally, as the doping concentration of N-epi increases, the number of carriers increases, and the depletion region narrows, resulting in a decrease in R_on,sp and BV. The optimized SJ VVD MOSFET exhibits a very high figure of merit (BFOM) of 13,400 KW/cm², indicating excellent performance characteristics and suggesting its potential as a next-generation highperformance power device suitable for practical applications.

• The Journal of the Convergence on Culture Technology
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• v.10 no.1
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• pp.379-386
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• 2024

The purpose of this study was to pay attention to the increase in the frequency of expression of butterflies and insects, whose decrease in the number of individuals is symbolized as a measure of environmental pollution, among the various motifs of nature as we go through the COVID-19, when we realized the importance of nature. The scope of this study was limited to fashion collection fashion show photos and interview articles of online for fashion collections from 2019 to 2023. As a result of the study, 185 butterfly motivation fashion design appeared, and digital printing techniques were the most used as a type of plane expression method. Along with this, techniques such as quilting, embroidery, and beading have appeared a lot as techniques to express the planar motif of butterflies. As for the three-dimensional expression types, 3D printing, laser cutting, corsage techniques, and draping techniques showed similar proportion. It can be seen that the expressed butterfly motif had more realistic description the shape of the butterfly as it was than abstract expressions. In conclusion, it can be seen that the butterfly motif fashion design over the past five years contains a stronger message about the environment than the butterfly motif fashion in the past. It was confirmed that it is a motif with a great symbolic meaning that can convey an eco-friendly message beyond just the morphological beauty and colorful design elements of the butterfly.

• Composites Research
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• v.37 no.3
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• pp.162-169
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• 2024

In this study, PAN(polyacrylonitrile)-based precursor fibers were produced through a wet-spinning process, and their morphologies and graphitization behavior were investigated in the presence of two graphitization catalysts (Ca, Ni). The graphitization catalysts were introduced into the formed pores during hot-water stretching of wet-spun PAN-based precursor fibers. The catalytic effects of graphitization catalysts were examined through crystal structure and Raman analysis. At a relatively low temperature of 1500℃, the graphitization was not significantly affected, whereas at a high temperature of 2400℃, the obtained I_D/I_G value of graphite fiber (GF-Ni100) was decreased by about twice (~0.28) compared to the untreated fibers (GF-AS~0.54). By comparing the I_D/I_G values (GF-Ca100~0.42: GF-Ni100~0.28) of Ca and Ni graphitization catalyst, it was found that the degree of graphitization of Ni graphitization catalyst showed higher influence than that of Ca graphitization catalyst. Moreover, 2D band was also observed, indicating that the graphite plane structures composed of multiple layers were developed. XRD results confirmed that the crystal inter-planar distance (d₀₀₂) of the graphite crystal was slightly decreased after the treatment with the graphitization catalyst, But, the crystal size of Ca-treated graphite fiber (GF-Ca100) was increased by up to ~5 nm.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.4
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• pp.16-21
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• 2017

In this paper, a Small-sized and planer resonator design of Magnetic Resonance - Wireless Power Transfer(MR-WPT) were proposed for practical applications of mobile devices, such as a laptop, a smart-phone and a tablet pc. The proposed MR-WPT system were based on four coil MR-WPT and designed as a transmitter part (Tx) and a receiver part (Rx) both are the same shape with the same loop and resonator. There are four different spiral coil type of resonators with variable of line length, width, gap and turns in $50mm{\times}50mm$ size. The both of top and bottom side of substrate(acrylic; ${\varepsilon}_r=2.56$, tan ${\delta}=0.008$) ere used to generate high inductance and capacitance in limited small volume. Loops were designed on the same plane of resonator to reduce their volume, and there are three different size. The proposed MR-WPT system were fabricated with two acrylic substrate plane of Tx and Rx each, the Rx and Tx loops and resonators were fabricated of copper sheets. There are 12 combinations of 3 loops and 4 resonators, each combination were measured to calculate transfer efficiency and resonance frequency in transfer distance from 1cm to 5cm. The measured results, the highest transfer efficiency was about 70%, and average transfer efficiency was 40%, on the resonance frequency was about 6.78 MHz, which is standard band by A4WP. We proposed small-sized and planer resonator of MR-WPT and showed possibility of mobile applications for small devices.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.33 no.2
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• pp.1-11
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• 2015

This study sheds light on a pond design process which is a core facility of Hwaseol-dang in Muan, the Jeonnam. The plasticity of the pond was analyzed and interpreted for the design process using methods such as "literature search, interview, site visits, aerial pictures, aerial photographing, drawing figures of configuration plane via measurements, internet search, etc.", to trace the developing process of the design and the implications therein. The study results being centered on the developing process of the pond design are summarized herein below. The position of the Hwaseol-dang, being formed on a low hill having low competence as a place for a pavilion, draws more attention regarding its implications from the aspect of inner design. The pond Hwaseol-dang is in a rectangular shape of 1 : 1.2 ratio, in which the depth is a bit higher on the pond edge of the Hwaseol-dang thus being slanted, and Crape Myrtle, which is not known whether introduced during the formation of the pond, is cultivated on the island in the center widespread toward the southeast region. The planar design of the pond is interpreted as "rectangular pond" but it has a smooth half-moon shape where a part is excluded to remove edge. In particular, the three islands in rectangular pond, due to the narrow area, put one island and two half-moon-shaped islands in juxtaposition, and thus, although only being one island, resultantly exhibits the existence effect of proliferated three islands. This is allegedly due to the intentional formation aiming at the effect of hybrid while minimizing the overlap due to merging and adding from the aspect of constituting a design. Furthermore, the pond Hwaseol-dang is extended northwest along with Hwaseol-dang, and also the island in the center is thought to additionally have one or two, but the widespread phenomenon of the island in the center appears to consider the effect of "sit view on the floor of the pavilion of Hwaseol-dang". Considering that even a few examples of ponds having the three islands among the private house gardens in the nation are all curved ponds, the characteristics of the rectangular Hwaseol-dang pond establishing the garden effect of the three islands by modifying the one island in rectangular pond is highly notable. Considering that the three islands of "Yeongju, Bangjang, and Bongrae" is the original shape of the pond garden gestating Taoist ideology, as a symbolic design of a pond, it is regarded as the characteristics of the pond shape in Jeonnam area, and the so-called three treasures "Hwaseol-dang, Camellia, and oddly shaped stones, etc." are concentrated as the symbolism of Hwaseol-dang pond.

• Journal of Animal Environmental Science
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• v.10 no.2
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• pp.93-100
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• 2004

An experiment was conducted to establish comparison of ventilation efficiency in an enclosed and conventional growing-finishing pig house. The experimental pigs were in winter and summer. The main results of the experiment are as follows : Then the air from planar slot inlet the pig house flow out through the sidewall outlet operated by exhaust fan(Gl). The second structure has an air input through the circular duct inlet are plated side the juncture of the entering wall and the air into the pig house flow out through the chimney and pit outlet are operated by exhaust fan(G2). Through the air into relay fan the pig house flow out through the curtains in sidewall(G3). Similarly, air comes in through the circular duct inlet are placed the air into the pig house flow out through the curtains in sidewall (G4). Air flow rate on the floor level which is the low part of pen and the living area of pigs in the G2 and G4 system during winter was measured at 0.2 to 0.3 m/s at the 0.5 to 0.6 m/s at the maximum ventilation efficiency. As for the results of detrimental gas(ammonia) concentration ratio analysis, while G2 and G4 system sustained of summer 13.3 $\~$ 16.6 ppm, winter 14.0 $\~$ 14.6 ppm level, Gl and G3 system sustained of summer 14.6 $\~$ 20.3 ppm, winter 20.3 $\~$ 25.0 ppm, and the latter one is lower than that of the G1 and G3 system.

• Progress in Medical Physics
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• v.20 no.4
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• pp.277-289
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• 2009

Recently, functional MRI has been used to investigate the neurobiological mechanisms of acupuncture and the specificity of acupoint. The group data tend to be regarded as more important than the individual data in the most of previous studies. This study was designed to investigate the effect of the variability of individual data on the group results. A functional MRI (fMRI) of the whole brain was performed in fifteen healthy subjects during placebo and acupuncture stimulations at the ST36 acupoint. After remaining at rest for 30 seconds, the acupuncture was inserted and twisted at the rate of 2 Hz for 45 seconds and then the acupuncture was removed immediately. This process was repeated three times. Individual and group analyses were performed by voxel-based analyses using SPM2 software. Visual inspections of the activation and deactivation maps from individual sessions have shown the large variability across fifteen subjects. This means that the group data reflected the brain activation responses of only a few subjects. We suggest that the individual data should be presented to demonstrate the effect of acupuncture.

• Investigative Magnetic Resonance Imaging
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• v.3 no.1
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• pp.47-52
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• 1999

Purpose : The purpose of this study was aimed to evaluate the BOLD(blood oxygen level dependent) contrast fMRI(functional MR imaging) in the occipital lobe and to compare with the metabolic changes based on H MRS (MR spectroscopy) and MRSI (MR spectroscopic imaging) before and after visual stimulation Materials and Methods : Healthy human volunteers (eight males and two females with 24-30 year age) participated in this study. All of the BOLD fMRI were acquired on a 1.5T MR with EPI during supervised visual stimulation in the occipital lobe. The red flicker with 8Hz was used for visual stimulation. After imaging acquisition, the MR images were transferred into unix workstation and processed with acquired from the same location based on the activation map. MRSI (magnetic resonance spectroscopic imaging) was also acquired to analyze the lactate changes before and after stimulation. Results : The activation maps were successfully produced by BOLD effect due to visual stimulation. NAA (N-acetyle aspartate)/Cr (creatine) ratio varied only from $1.79{\pm}0.28{\;}to{\;}1.88{\pm}0.20$ in activation area before and after stimulation. However, the signal intensity of lactate was elevated $9.48{\pm}4.38$ times higher than before activation. Lactate metabolite images were consistent with the activation maps. Conclusion : The BOLD contrast fMRI is enough sensitive to detect the activated area in human brain during the visual stimulation. Lactate metabolite map presents the evidence of lactate elevation on the same area of activation.

• Progress in Medical Physics
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• v.19 no.4
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• pp.209-218
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• 2008

According to improved radiation therapy technology such as IMRT and proton therapy, the accuracy of patient alignment system is more emphasized and IGRT is dominated research field in radiation oncology. We proposed to study the feasibility of cone-beam CT system using simple x-ray imaging systems for image guided proton therapy at National Cancer Center. 180 projection views ($2,304{\times}3,200$, 14 bit with 127 ${\mu}m$ pixel pitch) for the geometrical calibration phantom and humanoid phantoms (skull, abdomen) were acquired with $2^{\circ}$ step angle using x-ray imaging system of proton therapy gantry room ($360^{\circ}$ for 1 rotation). The geometrical calibration was performed for misalignments between the x-ray source and the flat-panel detector, such as distances and slanted angle using available algorithm. With the geometrically calibrated projection view, Feldkamp cone-beam algorithm using Ram-Lak filter was implemented for CBCT reconstruction images for skull and abdomen phantom. The distance from x-ray source to the gantry isocenter, the distance from the flat panel to the isocenter were calculated as 1,517.5 mm, 591.12 mm and the rotated angle of flat panel detector around x-ray beam axis was considered as $0.25^{\circ}$. It was observed that the blurring artifacts, originated from the rotation of the detector, in the reconstructed toomographs were significantly reduced after the geometrical calibration. The demonstrated CBCT images for the skull and abdomen phantoms are very promising. We performed the geometrical calibration of the large gantry rotation system with simple x-ray imaging devices for CBCT reconstruction. The CBCT system for proton therapy will be used as a main patient alignment system for image guided proton therapy.

• Investigative Magnetic Resonance Imaging
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• v.1 no.1
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• pp.119-124
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• 1997

Purpose: To assess the utility of magnetic resonance(MR) cerebral blood volume (CBV) map in the evaluation of brain tumors. Materials and Methods: We performed perfusion MR imaing preoperatively in the consecutive IS patients with intracranial masses(3 meningiomas, 2 glioblastoma multiformes, 3 low grade gliomas, 1 lymphoma, 1 germinoma, 1 neurocytoma, 1 metastasis, 2 abscesses, 1 radionecrosis). The average age of the patients was 42 years (22yr -68yr), composed of 10 males and S females. All MR images were obtained at l.ST imager(Signa, CE Medical Systems, Milwaukee, Wisconsin). The regional CBV map was obtained on the theoretical basis of susceptibility difference induced by first pass circulation of contrast media. (contrast media: IScc of gadopentate dimeglumine, about 2ml/sec by hand, starting at 10 second after first baseline scan). For each patient, a total of 480 images (6 slices, 80 images/slice in 160 sec) were obtained by using gradient echo(CE) single shot echo-planar image(EPI) sequence (TR 2000ms, TE SOms, flip angle $90^{\circ}$, FOV $240{\times}240mm,{\;}matrix{\;}128{\times}128$, slice-thick/gap S/2.S). After data collection, the raw data were transferred to CE workstation and rCBV maps were generated from the numerical integration of ${\Delta}R2^{*} on a voxel by voxel basis, with home made software (${\Delta}R2^{*}=-ln (S/SO)/TE). For easy visual interpretation, relative RCB color coding with reference to the normal white matter was applied and color rCBV maps were obtained. The findings of perfusion MR image were retrospectively correlated with Cd-enhanced images with focus on the degree and extent of perfusion and contrast enhancement. Results: Two cases of glioblastoma multiforme with rim enhancement on Cd-enhanced Tl weighted image showed increased perfusion in the peripheral rim and decreased perfusion in the central necrosis portion. The low grade gliomas appeared as a low perfusion area with poorly defined margin. In 2 cases of brain abscess, the degree of perfusion was similar to that of the normal white matter in the peripheral enhancing rim and was low in the central portion. All meningiomas showed diffuse homogeneous increased perfusion of moderate or high degree. One each of lymphoma and germinoma showed homogenously decreased perfusion with well defined margin. The central neurocytoma showed multifocal increased perfusion areas of moderate or high degree. A few nodules of the multiple metastasis showed increased perfusion of moderate degree. One radionecrosis revealed multiple foci of increased perfusion within the area of decreased perfusion. Conclusion: The rCBV map appears to correlate well with the perfusion state of brain tumor, and may be helpful in discrimination between low grade and high grade gliomas. The further study is needed to clarify the role of perfusion MR image in the evaluation of brain tumor.