• Journal of Yeungnam Medical Science
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• v.39 no.3
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• pp.200-205
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• 2022

Pain from nervous or musculoskeletal disorders is one of the most common complaints in clinical practice. Corticosteroids have a high pain-reducing effect, and their injection is generally used to control various types of pain. However, they have various adverse effects including flushing, hyperglycemia, allergic reactions, menstrual changes, immunosuppression, and adrenal suppression. Pulsed radiofrequency (PRF) is known to have a pain-reducing effect similar to that of corticosteroid injection, with nearly no major side effects. Therefore, it has been widely used to treat various types of pain, such as neuropathic, joint, discogenic, and muscle pain. In the current review, we outlined the pain-reducing mechanisms of PRF by reviewing previous studies. When PRF was first introduced, it was supposed to reduce pain by long-term depression of pain signaling from the peripheral nerve to the central nervous system. In addition, deactivation of microglia at the level of the spinal dorsal horn, reduction of proinflammatory cytokines, increased endogenous opioid precursor messenger ribonucleic acid, enhancement of noradrenergic and serotonergic descending pain inhibitory pathways, suppression of excitation of C-afferent fibers, and microscopic damage of nociceptive C- and A-delta fibers have been found to contribute to pain reduction after PRF application. However, the pain-reducing mechanism of PRF has not been clearly and definitely elucidated. Further studies are warranted to clarify the pain-reducing mechanism of PRF.

• Journal of Broadcast Engineering
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• v.16 no.5
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• pp.846-860
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• 2011

The binaural auditory system of human has ability to differentiate the direction and the distance of the sound sources by using the information which are inter-aural intensity difference(IID), inter-aural time difference(ITD) and/or the spectral shape difference(SSD). These information is generated from the acoustical transfer of a sound source to pinna, the outer ears. We can create a virtual sound system using the information which is called Head related transfer function(HRTF). However the performance of 3D sound is not always satisfactory because of non-individual characteristics of the HRTF. In this paper, we propose the algorithm that uses human's auditory characteristics for accurate perception. To achieve this, excitation energy of HRTF, global masking threshold and loudness are applied to the proposed algorithm. Informal listening test shows that the proposed method improves the sound localization characteristics much better than conventional methods.

• YAKHAK HOEJI
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• v.55 no.3
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• pp.247-250
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• 2011

An increase in ventricular pressure can alter cardiac excitation and contraction. Recent report has demonstrated that fluid pressure (FP) suppresses L-type $Ca^{2+}$ current with acceleration of the current inactivation in ventricular myocytes. Since the L-type $Ca^{2+}$ channels known to be regulated by intracellular pH ($pH_i$), this study was designed to explore whether pressurized fluid flow affects pHi in isolated rat ventricular myocytes. A flow of pressurized (~16 dyne/$cm^2$) fluid, identical to that bathing the myocytes, was applied onto single myocytes, and intracellular $H^+$ concentration was monitored using confocal $H^+$ imaging. FP significantly decreased $pH_i$ by $0.07{\pm}0.01$ pH units (n=16, P<0.01). Intracellular acidosis enhances the activity of $Na^+-H^+$ exchanger (NHE). Therefore, we examined if the NHE activity is increased by FP using the NHE inhibitor, HOE642. Although HOE642 did not alter $pH_i$ in control conditions, it decreased $pH_i$ in cells pre-exposed to FP, suggesting enhancement of NHE activity by FP. In addition, FP-induced intracellular acidosis was larger in cells pre-treated with HOE642 than in cells under the control conditions. These results suggest that FP induces intracellular acidosis and that NHE may contribute to extrude $H^+$ during the FP-induced acidosis in rat ventricular myocytes.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.636-636
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• 2013

Since first discovery of strong Raman spectrum of molecules adsorbed on rough noble metal, surface enhanced Raman scattering (SERS) has been widely used for detection of molecules with low concentration. Surface plasmons at noble metal can enhance Raman spectrum and using Au nanostructures as substrates of SERS has advantages due to it has chemical stability and biocompatibility. However, the photoluminescence (PL) background from Au remains a problem because of obtaining molecular vibration information. Recently, graphene, two-dimensional atomic layer of carbon atoms, is also well known as PL quenchers for electronic and vibrational excitation. In this study, we observed SERS of single layer graphene on or under monolayer of Au nanoparticles (NPs). Single layer graphene is grown by chemical vapor deposition and transferred onto or under the monolayer of Au NPs by using PMMA transfer method. Monolayer of Au NPs prepared using Langmuir-Blodgett method on or under graphene surface provides closed and well-packed monolayer of Au NPs. Scanning electron microscopy (SEM) and Raman spectroscopy (WItec, 532 nm) were performed in order to confirm effects of Au NPs on enhanced Raman spectrum. Highly enhanced Raman signal of graphene by Au NPs were observed due to many hot-spots at gap of closed well-packed Au NPs. The results showed that single layer graphene provides larger SERS effects compared to multilayer graphene and the enhancement of the G band was larger than that of 2D band. Moreover, we confirm the appearance of D band in this study that is not clear in normal Raman spectrum. In our study, D band appearance is ascribed to the SERS effect resulted from defects induced graphene on Au NPs. Monolayer film of Au NPs under the graphene provided more highly enhanced graphene Raman signal compared to that on the graphene. The Au NPs-graphene SERS substrate can be possibly applied to biochemical sensing applications requiring highly sensitive and selective assays.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.76-76
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• 2008

The resonance properties due to the surface plasmon(SP) excitation of metal nanoparticles make the nanocomposite films promising for various applications such as optical switching devices. In spite of the well-known ultra-sensitive operation of optical switches based on a guided wave, the application of nanocomposite film(NC) has inherent limitation originating from the excessive optical loss related with the surface plasmon resonance(SPR). In this study, we addressed this problem and present the experimental and theoretical analysis on the pump-probe optical switching in prism-coupled Au(1 vol.%):$SiO_2$ nanocomposite waveguide film. The guided mode was successfully generated using a near infrared probe beam of 1550 nm and modulated with an external pump beam of 532 nm close to the SPR wavelength. We extend our approach to ultra-fast operation using a pulsed laser with 5 ns pulse width. To improve the switching speed through the reduction in thermal loading effect accompanied by the resonant absorption of pump beam light, we adopted a metallic film as a coupling layer instead of low-index dielectric layer between the high-index SF10 prism and NC slab waveguide. We observed great enhancement in switching speed for the case of using metallic coupling layer, and founded a distinct difference in origin of optical nonlinearities induced during switching operation using cw and ns laser.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.10
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• pp.1845-1851
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• 2007

Background noise and room reverberation are two causes of degradation in speech in listening situations. Many algorithms developed to enhance reverberant speech. In this paper we propose a dereverberation method for enhancement of speech using modified the linear prediction(LP) residual in reverberant room condition. The proposed dereberberation method based on the fact that the signification excitation of the vocal tract system takes place at the instant of glottal closure in voiced speech. Our method used delay information form each sensor, and we need reverberant signals from 3 sensors. We obtain a new LP residual signal using modified IP residual combination which derived form weighting of the LP residual and the Hilbert transform of LP residual. The nature of the coherently added Hilbert envelop has several large amplitude spikes because of the effects of noise and reverberation. This residual of the clean speech is used to excite the time-varying all-pole filter to obtain the enhanced speech. We achieved simulation of proposed algorithm for performance analysis in reverberation environment. The proposed algorithm improves substantially the quality of reverberant speech.

• Korean Journal of Materials Research
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• v.29 no.9
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• pp.559-566
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• 2019

$Lu(Nb,Ta)O_4:Eu^{3+}$ powders are synthesized by a solid-state reaction process using LiCl and $Li_2SO_4$ fluxes. The photoluminescence (PL) excitation spectra of the synthesized powders consist of broad bands at approximately 270 nm and sharp peaks in the near ultraviolet region, which are assigned to the $Nb^{5+}-O^{2-}$ charge transfer of $[NbO_4]^{3-}$ niobates and the f-f transition of $Eu^{3+}$, respectively. The PL emission spectra exhibit red peaks assigned to the $^5D_0{\rightarrow}^7F_J$ transitions of $Eu^{3+}$. The strongest peak is obtained at 614 nm ($^5D_0{\rightarrow}^7F_2$), indicating that the $Eu^{3+}$ ions are incorporated into the $Lu^{3+}$ asymmetric sites. The addition of fluxes causes the increase in emission intensity, and $Li_2SO_4$ flux is more effective for enhancement in emission intensity than is LiCl flux. The substitution of $Ta^{5+}$ for $Nb^{5+}$ results in an increase or decrease in the emission intensity of $LuNb_{1-x}Ta_xO_4:Eu^{3+}$ powders, depending on amount and kind of flux. The findings are explained using particle morphology, modification of the $[NbO_4]^{3-}$ structure, formation of substructure of $LuTaO_4$, and change in the crystal field surrounding the $Eu^{3+}$ ions.

• Investigative Magnetic Resonance Imaging
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• v.5 no.1
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• pp.18-23
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• 2001

Purpose : To describe the MRI findings in the bronchial anthracofibrosis mimicking lung cancer on CT examination. Materials and methods : Ten patients, who showed CT findings mimicking lung cancer, were selected among fifty patients of bronchial anthracofibrosis proven by bronchoscopic biopsy, consisting of two men and eight women, ranging in age from 58 to 79 years old faverage age, 68 years old). CT scan and MRI were performed in all patients (n=10). Percutaneous lung biopsy on mass was performed in one patient. MRI findings were analyzed with the emphasis on the signal intensity of the mass (n=4), collapsed lung (n=4) and Iymph node (n=10) on axial T1 and T2-weighted images by two radiologists in consensus. No contrast enhancement was used in all cases. Results : CT scan revealed mass (n=4), atelectasis with obstructive pneumonia(n=4) and bronchial wall thickening(n=2). All patients showed enlarged medistinal Iymph nodes(n=10). The mass showed low signal intensity on T1WI and T2WI (n =4). The collapsed lung in patients with atelectasis indicated intermediate signal intensity on T1WI and low signal intensity on T2WI (n= 4). Nine patients showed low sisnal intensity of Iymph node on T1WI and T2WI, except one patient who showed central high signal intensity with peripheral rim of low signal intensity in right lower paratracheal llmph node on T2WI. Conclusion : Low signal intensity of a mass, collapsed lung, and lymph nodes on T2WI in anthracofibrosis patients may be helpful in differentiation of the lesion from lung cancer.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.5
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• pp.426-431
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• 2007

When a high-energy ultrasound propagates through a solid body that contains a crack or a delamination, the two faces of the defect do not ordinarily vibrate in unison, and dissipative phenomena such as friction, rubbing and clapping between the faces will convert some of the vibrational energy to heat. By combining this heating effect with infrared imaging, one can detect a subsurface defect in material in real time. In this paper a realtime detection of the brazing defect of thin Inconel plates using the UIR (ultrasonic infrared imaging) technology is described. A low frequency (23 kHz) ultrasonic transducer was used to infuse the welded Inconel plates with a short pulse of sound for 280 ms. The ultrasonic source has a maximum power of 2 kW. The surface temperature of the area under inspection is imaged by an infrared camera that is coupled to a fast frame grabber in a computer. The hot spots, which are a small area around the bound between the two faces of the Inconel plates near the defective brazing point and heated up highly, are observed. And the weak thermal signal is observed at the defect position of brazed plate also. Using the image processing technology such as background subtraction average and image enhancement using histogram equalization, the position of defective brazing regions in the thin Inconel plates can be located certainly.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.276-276
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• 2010

Localized surface plasmon resonance (LSPR) has been explored recently as a promising approach to increase energy conversion efficiency in photovoltaic devices, particularly for thin film hydrogenated amorphous silicon (a-Si:H) solar cells. The LSPR is frequently excited via an electromagnetic (EM) radiation in proximate metallic nanostructures and its primary con sequences are selective photon extinction and local EM enhancement which gives rise to improved photogeneration of electron-hole (e-h) pairs, and consequently increases photocurrent. In this work, high-dielectric-constant (k) $ZrO_2$ (refractive index n=2.22, dielectric constant $\varepsilon=4.93$ at the wavelength of 550 nm) is proposed as spacing layer to enhance the LSPR for application to the thin film silicon solar cells. Compared to excitation of the LSPR using $SiO_2$ (n=1.46, $\varepsilon=2.13$ at the wavelength of 546.1 nm) spacing layer with Au nanoparticles of the radius of 45nm, that using $ZrO_2$ dielectric shows the advantages of(i) ~2.5 times greater polarizability, (ii) ~3.5 times larger scattering cross-section and ~1.5 times larger absorption cross-section, (iii) 4.5% higher transmission coefficient of the same thickness and (iv) 7.8% greater transmitted electric filed intensity at the same depth. All those results are calculated by Mie theory and Fresnel equations, and simulated by finite-difference time-domain (FDTD) calculations with proper boundary conditions. Red-shifting of the LSPR wavelength using high-k $ZrO_2$ dielectric is also observed according to location of the peak and this is consistent with the other's report. Finally, our experimental results show that variation of short-circuit current density ($J_{sc}$) of the LSPR enhanced a-Si:H solar cell by using the $ZrO_2$ spacing layer is 45.4% higher than that using the $SiO_2$ spacing layer, supporting our calculation and theory.