• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2001.11a
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• pp.464-468
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• 2001

In this paper, we propose a robust watermarking technique that accepts time scaling, pitch shift, add noise and a lot of lossy compression such as MP3, AAC, WMA. The technique is developed based on digital filtering. Being designed according to critical band of HAS (human auditory system), the digital filters nearly affect audio quality. Furthermore, before implementing digital filtering, wavelet transform decomposes the audio signal into several signals that is composed of specific frequencies. Designed digital filters scan the decomposed signal. The designed digital filter, band-stop filter, distorts and eliminates specific frequencies of audio signals. Watermarking detection can be accomplished by FFT (Fast Fourier Transform). Firstly, segments of audio signal are transformed by FFT. Then, the obtained amplitude spectrum by FFT is summed repeatedly. Finally the watermark detector can find filters used to watermark encoding based on eliminating frequencies. The suggested technique can embed 4bits/s in a robust manner.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.591-594
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• 2005

Islanding of PV systems occurs when the uitilty grid is removed but local sources continue to operate and provide power to local loads. Islanding Is one of the serious problems in an electric power system connected with dispersed power sources. Also, this scan present safety hazards and the possibility of damage to other electric equipments. If the real and reactive power of RLC load and PV system are closely matched, islanding phenomena can't be detected by the passive methods. Several active methods were proposed to detect islanding phenomena. The most effective method is SFS method which was suggested by Sandia National Laboratory. In this paper, a new anti-islanding algorithm is proposed and its validity is verified through simulation and experimental results for utility interconnection of PV system.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.59-65
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• 2008

The purpose of this study was to investigate the shift of COP pathway and the plantar foot pressure among level walking and stairs and ramp climbing in young and elderly people. Plantar foot pressure was measured by MatScan system(Tekscan, USA). Statistical analysis was used One-way ANOVA to know the characteristics of peak plantar pressure during walking with different the facilities. In young adults, COP pathway during stairs climbing was slightly shorten and trended to abduct at forefoot. COP pathway during ramp climbing was also shorten but trend to adduct at forefoot. Peak plantar pressure of 2-3 metatarsal head and heel during ramp climbing was more decreased than level walking. In elderly people, COP pathway during stairs climbing was more shorten and abducted than leve walking and COP pathway during ramp climbing was more unstable than level walking. Peak plantar pressure of first metatarsal head increased at stair climbing and decreased at ramp climbing. That of second metatarsal head and heel was more decreased at ramp climbing. Conclusionally, Peak plantar pressures of each foot region generally increased and more changed during ramp climbing.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.422.1-422.1
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• 2016

Graphene quantum dots (GQDs), a new kind of carbon-based photo luminescent nanomaterial from chemically modified graphene oxide (CMGO) or chemically modified graphene (CMG), has attracted extensive research attention in the last few years due to its outstanding chemical, optical and electrical properties. To further extended its potential applications as optoelectronic devices, solar cells, bio and bio-sensors and so on, intensive research efforts have been devoted to the CMG. However, the CMG, a suspension of aqueous, have problematic since they are prone to agglomeration after drying a solvent. In this study, we synthesized the GQDs from graphite and deposited on silicon substrate by kinetic spray. The photo luminescent properties of deposited GQD films were analyzed and compared with initial GQDs suspension. In addition, its carbon properties were investigated with GQDs solution properties. The properties of deposited GQD films by kinetic spray were similar to that of the GQDs suspension in water. We could provide a pathway for silicon-based silicon based device applications. Finally, the well-adjusted GQD films with photo luminescence effects will show Energy-Down-Shift layer effects on silicon solar cells. The GQD layers deposited at nozzle scan speeds of 40, 30, 20, and 10 mm/s were evaluated after they were used to fabricate crystalline-silicon solar cells; the results indicate that GQDs play an important role in increasing the optical absorptivity of the cells. The short-circuit current density (Jsc) was enhanced by about 2.94 % (0.9 mA/cm2) at 30 mm/s. Compared to a reference device without a GQD energy-down-shift layer, the PCE of p-type silicon solar cells was improved by 2.7% (0.4 percentage points).

• Journal of Korean Foot and Ankle Society
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• v.12 no.1
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• pp.41-46
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• 2008

Purpose: This study was designed to evaluate characteristics of foot pressure distribution with or without partial prosthetic foot in transmetatarsal amputee. Materials and Methods: The subjects were 9 transmetatarsal amputees. Foot pressures were measured at hallux, the $1^{st}-5^{th}$ metatarsal head (MTH), mid-foot, condyle area by F-scan system in amputated or contralateral foot during active walking. Results: In amputated foot, mean peak pressure was greatest in midfoot without prosthetic foot but it was greatest in hindfoot with prosthetic foot. In unaffected foot, although mean peak pressure was higher in hallux, and $1-5^{th}$ MTH compared to amputated foot, it was greatest in hind foot both with and without prosthetic foot. However, in unaffected foot, mean peak pressure significantly decreased in hallux and $5^{th}$ MTH after wearing the prosthetic foot. There was a significant difference in mean peak pressure in hallux and $5^{th}$ MTH between amputated and unaffected foot after wearing prosthetic foot. However, other region had no significant difference with or without prosthetic foot between feet. Conclusions: The use of partial prosthetic foot tends to shift weight bearing from the heel area to forefoot and could significantly reduce hind foot peak pressure and redistributed to peak pressure. The partial prosthetic foot can also offer the peak pressure to reduction both amputated foot and unaffected foot and help to toe off during walking.

• Archives of Craniofacial Surgery
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• v.21 no.5
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• pp.309-314
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• 2020

Reconstructions of extensive composite scalp and cranial defects are challenging due to high incidence of postoperative infection and reconstruction failure. In such cases, cranial reconstruction and vascularized soft tissue coverage are required. However, optimal reconstruction timing and material for cranioplasty are not yet determined. Herein, we present a large skull defect with a chronically infected wound that was not improved by repeated debridement and antibiotic treatment for 3 months. It was successfully treated with anterolateral thigh (ALT) free flap transfer for wound salvage and delayed cranioplasty with a patient-specific polyetheretherketone implant. To reduce infection risk, we performed the cranioplasty 1 year after the infection had resolved. In the meantime, depression of ALT flap at the skull defect site was observed, and the midline shift to the contralateral side was reported in a brain computed tomography (CT) scan, but no evidence of neurologic deterioration was found. After the surgery, sufficient cerebral expansion without noticeable dead-space was confirmed in a follow-up CT scan, and there was no complication over the 1-year follow-up period.

• Nuclear Medicine and Molecular Imaging
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• v.41 no.4
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• pp.339-341
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• 2007

A 22-year-old woman with a history of acute lymphoblastic leukemia was hospitalized for headache and vomiting. CT scan showed a well-defined, ring like enhancing mass in the left frontal lobe with surrounding edema and midline shift. Magnetic resonance imaging demonstrated a round homogeneous mass with a ring of enhancement in the left frontal lobe. Tl-201 brain SPECT showed increased focal uptake coinciding with the CT and MRI abnormality. Aspiration of the lesion performed through a burr hole yielded many neutrophils, a few lymphocytes and histiocytes with some strands of filamentous microorganism-like material. Modified AFB stained negative for norcardia. Gram stain showed a few white blood cells and no microorganism. Antibiotics were started and produced a good clinical response. After one month, CT scan showed markedly reduction in size and extent was observed.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.46.1-46.1
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• 2018

The Fast Imaging Solar Spectrograph (FISS) on the Goode Solar Telescope (GST) at Big Bear Solar Observatory is the imaging Echelle spectrograph developed by the Solar Astronomy Group of Seoul National University and the Solar and Space Weather Group of Korea Astronomy and Space Science Institute. The instrument takes spectral data from a region on the Sun in two spectral bands simultaneously. The imaging is done by the organization of intensity data obtained from the fast raster scan of the slit over the field of view. Since the scan repeats many times, the whole set of data can be used to construct the movies of monochromatic intensity at arbitrary wavelengths within the spectral bands, and those of line-of-sight velocity inferred from different spectral lines. So far there are two standard observing configurations: one recording the $H{\alpha}$ line and the Ca II 8542 line simultaneously, and the other recording the Na I D2 line and Fe I 5435 line simultaneously. We have developed the procedures to produce the standard data for each observing configuration. The procedures include the spatial alignment, the correction of spectral shift of instrumental origin, and the lambdameter measurement of the line wavelength. The standard data include the movie of continuum intensity, the movies of intensity and velocity inferred from a chromospheric spectral line, the movies of intensity and velocity inferred from a photospheric line. The processed standard data will be freely available online (fiss.snu.ac.kr) to be used for research and public outreach. Moreover, the IDL procedures will be provided on request as well so that each researcher can adapt the programs for their own research.

• Current Optics and Photonics
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• v.7 no.6
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• pp.721-731
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• 2023

This paper studies various roughness parameters, besides waviness, texture, and nonlinear parameters of Bismarck brown Y (BBY)-doped Poly(methyl methacrylate) (PMMA) films based on the computed values of optical limiting (OL) threshold power and nonlinear refractive index. The films' morphology, grain size, and absorption spectra were investigated using atomic force microscopy in conjunction with ultraviolet-visible (UV-Vis) spectrophotometer. The particle size of the films ranged between 4.11-4.51 mm and polymer films showed good homogeneity and medium roughness, ranging from 1.11-4.58 mm. A polymer film's third-order nonlinear optical features were carried out using the Z-scan methodology. The measurements were obtained by a continuous wave produced from a solid-state laser with a 532 nm wavelength. According to the results, BBY has a nonlinear refractive index of 10^-6 cm²/W that is significantly negative and nonlinear. The optical limiting thresholds are roughly 10.29, 13.52, and 18.71 mW, respectively. The shift of nonlinear optical features with the film's concentration was found throughout the experiment Additionally, we found that the polymer samples have outstanding capabilities for restricting the amount of optical power that may be transmitted through them. We propose that these films have the potential to be used in a wide variety of optoelectronic applications, including optical photodetectors and optical switching.

• Journal of Korean Neurosurgical Society
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• v.42 no.4
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• pp.331-336
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• 2007

Objective : The aim of this study was to analyze the treatment results and prognostic factors in patients with massive cerebral infarction who underwent decompressive craniectomy. Methods : From January 2000 to December 2005, we performed decompressive craniectomy in 24 patients with massive cerebral infarction. We retrospectively reviewed the medical records, radiological findings, initial clinical assessment using the Glasgow Coma Scale, serial computerized tomography (CT) with measurement of midline and septum pellucidum shift, and cerebral infarction territories. Patients were evaluated based on the following factors : the pre- and post-operative midline shifting on CT scan, infarction area or its dominancy, consciousness level, pupillary light reflex and Glasgow Outcome Scale. Results : All 24 patients (11 men, 13 women; mean age, 63 years; right middle cerebral artery (MCA) territory, 17 patients; left MCA territory, 7 patients) were treated with large decompressive craniectomy and duroplasty. The average time interval between the onset of symptoms and surgical decompression was 2.5 days. The mean Glasgow Coma Scale was 12.4 on admission and 8.3 preoperatively. Of the 24 surgically treated patients, the good outcome group (Group 2 : GOS 4-5) comprised 9 cases and the poor outcome group (Group1 : GOS 1-3) comprised 15 cases. Conclusion : We consider decompressive craniectomy for large hemispheric infarction as a life-saving procedure. Good preoperative GCS, late clinical deterioration, small size of the infarction area, absence of anisocoria, and preoperative midline shift less than 11mm were considered to be positive predictors of good outcome. Careful patient selection based on the above-mentioned factors and early operation may improve the functional outcome of surgical management for large hemispheric infarction.