• 한국전기전자재료학회논문지
• /
• 제27권10호
• /
• pp.630-634
• /
• 2014

$(Na_{0.525}K_{0.4425}Li_{0.0375})(Nb_{0.9975}Sb_{0.065}Ta_{0.0375})O_3+0.3 wt%CoO$ ceramics were fabricated as a function of CuO addition by traditional solid state sintering process in order to develop excellent lead-free piezoelectric ceramics composition. The addition of CuO in the LNKNTS composition ceramics can effectively enhance the densification of the ceramics, resulting in the oxygen vacancies as hardening effect. The excellent piezoelectric properties of electromechanical coupling factor($k{\small}_P$) of 0.378, piezoelectric constant($d_{33}$) of 152 pC/N were obtained from the 1.0 mol% CuO doped LNKNTS ceramics sintered at $1,020^{\circ}C$ for 3 h.

• 대한청각학회지
• /
• 제25권1호
• /
• pp.36-42
• /
• 2021

Background and Objectives: Globally, the human immunodeficiency virus (HIV) is responsible for one of the most serious pandemics to date. The vulnerability of the vestibular system in individuals with HIV has been confirmed, and central vestibular impairments have been frequently reported. However, there are disagreements on the impact of HIV on peripheral vestibular function. Thus, the current study aimed to determine the prevalence of peripheral vestibular impairment, specifically related to the semi-circular canals (SCCs), in HIV-positive individuals receiving antiretroviral (ARV) treatment. Subjects and Methods: A total of 92 adults between the ages of 18 and 50 years (divided into two groups) participated in the study. The first group comprised HIV-positive individuals receiving ARV treatment (n₁=60), and the second group comprised HIV-negative participants (n₂=32). The video head impulse test was used to conduct the head impulse paradigm (HIMP). Results: Bilateral normal HIMP results were obtained in 95% of the HIV-positive participants and all HIV-negative participants. The gain of the left posterior SCCs was significantly lower in the HIV-positive group, while the gains of all other canals between the two groups were comparable. Conclusions: The prevalence of peripheral vestibular impairment in the HIV-positive group was not significantly different from that of the HIV-negative group. The reduced prevalence in the current study may be attributed to participant characteristics, the test battery employed, and the central compensation of the vestibular dysfunctions at the later stages of infection.

• Journal of Audiology & Otology
• /
• 제25권1호
• /
• pp.36-42
• /
• 2021

Background and Objectives: Globally, the human immunodeficiency virus (HIV) is responsible for one of the most serious pandemics to date. The vulnerability of the vestibular system in individuals with HIV has been confirmed, and central vestibular impairments have been frequently reported. However, there are disagreements on the impact of HIV on peripheral vestibular function. Thus, the current study aimed to determine the prevalence of peripheral vestibular impairment, specifically related to the semi-circular canals (SCCs), in HIV-positive individuals receiving antiretroviral (ARV) treatment. Subjects and Methods: A total of 92 adults between the ages of 18 and 50 years (divided into two groups) participated in the study. The first group comprised HIV-positive individuals receiving ARV treatment (n₁=60), and the second group comprised HIV-negative participants (n₂=32). The video head impulse test was used to conduct the head impulse paradigm (HIMP). Results: Bilateral normal HIMP results were obtained in 95% of the HIV-positive participants and all HIV-negative participants. The gain of the left posterior SCCs was significantly lower in the HIV-positive group, while the gains of all other canals between the two groups were comparable. Conclusions: The prevalence of peripheral vestibular impairment in the HIV-positive group was not significantly different from that of the HIV-negative group. The reduced prevalence in the current study may be attributed to participant characteristics, the test battery employed, and the central compensation of the vestibular dysfunctions at the later stages of infection.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
• /
• pp.169-172
• /
• 2008

Land-use or land-cover classification of satellite images is one of the important tasks in remote sensing application and many researchers have been tried to enhance classification accuracy. Previous studies show that the classification technique based on wavelet transform is more effective than that of traditional techniques based on original pixel values, especially in complicated imagery. Various wavelets can be used in wavelet transform. Wavelets are used as basis functions in representing other functions, like sinusoidal function in Fourier analysis. In these days, some basis functions such as Haar, Daubechies, Coiflets and Symlets are mainly used in 2D image processing. Selecting adequate wavelet is very important because different results could be obtained according to the type of basis function in classification. However, it is not easy to choose the basis function which is effective to improve classification accuracy. In this study, we computed the wavelet coefficients of satellite image using 10 different basis functions, and then classified test image. After evaluating classification results, we tried to ascertain which basis function is the most effective for image classification. We also tried to see if the optimum basis function is decided by energy parameter before classifying the image using all basis function. The energy parameter of signal is the sum of the squares of wavelet coefficients. The energy parameter is calculated by sub-bands after the wavelet decomposition and the energy parameter of each sub-band can be a favorable feature of texture. The decision of optimum basis function using energy parameter in the wavelet based image classification is expected to be helpful for saving time and improving classification accuracy effectively.

• 디지털융복합연구
• /
• 제17권9호
• /
• pp.271-278
• /
• 2019

본 연구의 목적은 가상현실 훈련이 아급성 뇌졸중 환자의 상지기능과 일상생활활동에 미치는 효과를 규명하는 것이다. 아급성기 뇌졸중 환자 18명이 본 연구에 참여하였다. 모든 대상자는 실험군 9명과 대조군 9명으로 배정되었다. 두 군은 하루 30분, 주 5회, 4주 동안 보편적인 작업치료를 받았다. 실험군은 가상현실 훈련을 회기 마다 30분 더 받았으며, 대조군은 보편적인 작업치료를 회기 마다 30분 더 받았다. 결과 측정은 중재 전과 후에 Fugl-Meyer 평가와 한국판 수정바델지수에 의해 수행되었다. 연구 결과, 실험군은 중재 후 Fugl-Meyer 평가 점수와 한국판 수정바델지수 점수에서 유의한 향상을 보였다(p<.05). 대조군은 Fugl-Meyer 평가의 어깨/팔꿈치/전완, 손목, 손 하위항목과 한국판 수정바델지수에서 유의한 향상을 보였다(p<.05). 중재 후 실험군은 대조군보다 Fugl-Meyer 평가의 총점, 손목과 손하위항목에서 유의하게 더 큰 향상을 보였다(p<.05). 이러한 결과들은 가상현실 훈련이 아급성기 뇌졸중 환자의 상지기능 향상에 긍정적인 효과를 나타낼 수 있음을 시사한다.

• International Journal of Stem Cells
• /
• 제15권2호
• /
• pp.155-163
• /
• 2022

Background and Objectives: Mesenchymal stem cells (MSCs) have immunomodulatory function and participate in the pathogenesis of many immunoregulation-related diseases, including psoriasis. Previously, we found that MSCs from psoriatic lesions overexpress the proinflammatory microRNA, miR-155 and exhibit a decreased immunosuppressive capacity. But the origin of these aberrant characteristics is still not clear. To investigate whether inflammatory cytokines in serum and peripheral blood mononuclear cells (PBMCs) from psoriatic patients can regulate the expression patterns of immunoregulation-related cytokines and the immunoregulation function of MSCs. Methods and Results: Normal dermal mesenchymal stem cells (nDMSCs) were treated with serum or PBMCs derived from patients with psoriasis or healthy donors. Expression of miR-155 and immunoregulation-related genes in each MSCs were measured using real-time PCR or western-blot. Meanwhile, the immunosuppressive capacity of DMSCs was evaluated by its inhibitory ability on proliferation of activated PBMCs. Compared to control serum, psoriatic serum significantly increased the expression levels of miR-155 (27.19±2.40 vs. 3.51±1.19, p<0.001), while decreased TAB₂ expression (0.28±0.04 vs. 0.72±0.20, p<0.01) in DMSCs. Expression levels of immunoregulation-related genes such as PGE₂, IL-10, and TLR4 were also markedly down-regulated following the psoriatic serum treatment. Those DMSCs treated with healthy serum could inhibit PBMC proliferation, while those psoriatic serum-treated DMSCs could not inhibit PBMC proliferation effectively. Conclusions: Psoriatic serum up-regulate the expression of miR-155, down-regulate the expression of immunoregulation-related genes (PGE₂, IL-10, and TLR4) in DMSCs, and along with the inhibition of the immunosuppressive function of MSCs.

• 대한수학회지
• /
• 제38권2호
• /
• pp.311-319
• /
• 2001

We show that it is possible to associate diffusion processes to second order perturbations of the Ornstein-Uhlenbeck operator L on the Wiener space of the form L = L + 1/2∑L$^2$(sub)ξ(sub)$\kappa$ where the ξ(sub)$\kappa$ are "tangent processes" (i.e., semimartingales with antisymmetric diffusion coefficients).

• Nuclear Engineering and Technology
• /
• 제52권6호
• /
• pp.1297-1303
• /
• 2020

In this study, nuclear radiation shielding and rigidity parameters of Y (0.1-x)B0.6Bi1.8O3La2x glassy system were investigated in order to determine it's suitability for use as nuclear radiation shielding materials. Therefore, a group of bismuth borate glass samples with La₂O₃ additive were synthesized using the technique of melt quenching. According to the results, the increase of the La₂O₃ additive increases the density of the glass samples and the mass attenuation coefficient (μ_m) values, whereas the half-value layer (HVL) and mean free path (MFP) values decrease. The effective atomic number (Z_eff) is also enhanced with an increment of both mass removal cross section for neutron (Σ_R) and absorption neutron scattering cross section (σ_abs). In addition to the other parameters, rigidity parameter values were theoretically examined. The increase of La₂O₃ causes some other important magnitudes to increase. These are the average crosslink density, the number of bonds per unit volume, as well as the stretching force constant values of these glass samples. These results are in concordance with the increase of elastic moduli in terms of the Makishima-Mackenzie model. This model showed an increase in the rigidity of the glass samples as a function of La₂O₃.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 추계학술대회 논문집
• /
• pp.255-258
• /
• 2000

In this study, the structural, dielectric and piezoelectric properties of Pb[(Sb$\sub$1/2/Nb$\sub$1/2/)$\sub$x/- (Ni$\sub$1/3/Nb$\sub$2/3/)$\sub$0.15-x/- (Zr,Ti)$\sub$0.85/]O$_3$(x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) ceramics is investigated as a function of Pb(Sb$\sub$1/2/Nb$\sub$1/2/)O$_3$ (abbreviated PSN) substitution. With the increase of PSN substitution, the crystal structure is transO$_3$formed from the tetragonal phase to the rhombohedral phase and the grain size is decreased abruptly. The curie temperature is decreased with the PSN substitution. The dielectric constant is increased with the PSN substitution and maximum value of 2290 is obtained at 4mol% PSN. With the PSN substitution, the coercive field is increased and the remnant polarization is decreased. The Electromechanical coupling factor(k$\sub$p/) Is showed the highest value of 0.622 at lmol% PSN and the mechanical quality factor(Q$\sub$m/) is decreased abruptly with the PSN substitution.

• 한국전기전자재료학회논문지
• /
• 제24권7호
• /
• pp.559-562
• /
• 2011

In this study, the effect of $Nb_2O_5$ and sintering time on the positive temperature of coefficient of resistivity (PTCR) behavior of lead free $Ba_{0.99}(Bi_{0.5}Na_{0.5})_{0.01}TiO_3$ (BBNT) ceramics were investigated in order to fabricate a PTC thermistor with high $T_c$ temperature more than $140^{\circ}C$. In particular, BBNT ceramic doped with 0.1mol% $Nb_2O_5$ and sintered at $1350^{\circ}C$ for 4 h has significantly increased Curie temperature ($T_c$) of about $200^{\circ}C$, showed good PTCR behavior of room-temperature resistivity ($\rho_{rt}$) of $40{\Omega}{\cdot}cm$, a high $\rho_{max}/\rho_{min}$ ratio of $43.78{\times}10^3$ and a large resistivity temperature factor (${\alpha}$) of 16.1%/$^{\circ}C$. With increasing addition of $Nb_2O_5$ content, the $\rho_{rt}$ decreased to a minimum value of $40\;{\Omega}cm$ at 0.1mol% $Nb_2O_5$ and the $\rho_{rt}$ increased for x value over 0.1 mol%.