• Applied Microscopy
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• 제39권2호
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• pp.175-183
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• 2009

이 논문에서 50 pm 이하의 원자열 분해상을 효과적으로 보여 주는 결정 밑 표면 파동함수(EPW)의 음(-)의 2차 도함수의 시뮬레이션 영상들이 나타나 있다. 그리고 해당 EPW는 HRTEM에서 일련의 비 초점 단계의 관찰 영상으로부터 얻을 수 있다. 이 논문에 나타난 시뮬레이션한 영상들은 대체로 50 pm 이하의 원자열 간격을 주는 Si과 InAs의 [114] 및 [116] 방위 축에 대한 것이다. 이 방법의 정당성에 대한 이론적 이유가 운동학적 회절이론을 기초로 한 분석에서 주어졌다. 그리고 그 응용성의 한계도 논의되었다.

• 전기학회논문지
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• 제62권10호
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• pp.1425-1435
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• 2013

The useful method for determining parameters of weighting functions used to design the $H_{\infty}$ current controller for attenuating the current ripple due to saliencies which SPMSM(Surface Permanent Magnet Synchronous Motor) also incorporates is described. To analyze the effect, the current ripple due to the structural and the saturation saliencies, the SPMSM model with nonlinear inductance function depending on the two independent variables, rotor position and stator current is simulated. After analysis, parameters of the weighting functions for $H_{\infty}$ current controller is selected to satisfy the robust stability, robust performance and specific performance in time and frequency domain by using the PSO(Particle Swarm Optimization) algorithm in the linear SPMSM model. Especially, the robust performance is proved that the selected weighting functions play a role in reducing the current ripple caused by the saliencies of SPMSM at the desired frequency range by the simple experiment.

• 대한수학회논문집
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• 제32권1호
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• pp.55-64
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• 2017

For -2 < ${\alpha}$ < ${\infty}$ and 0 < p < ${\infty}$, the $\mathcal{Q}_K$-type space is the space of all analytic functions on the open unit disk ${\mathbb{D}}$ satisfying $$_{{\sup} \atop a{\in}{\mathbb{D}}}{\large \int_{\mathbb{D}}}{{\mid}f^{\prime}(z){\mid}}^p(1-{{\mid}z{\mid}^2})^{\alpha}K(g(z,a))dA(z)<{\infty}$$, where $g(z,a)=log\frac{1}{{\mid}{\sigma}_a(z){\mid}}$ is the Green's function on ${\mathbb{D}}$ and K : [0, ${\infty}$) [0, ${\infty}$), is a right-continuous and non-decreasing function. For 0 < s < ${\infty}$, the space $\mathcal{Q}_s$ consists of all analytic functions on ${\mathbb{D}}$ for which $$_{sup \atop a{\in}{\mathbb{D}}}{\large \int_{\mathbb{D}}}{{\mid}f^{\prime}(z){\mid}}^2(g(z,a))^sdA(z)<{\infty}$$. Boundedness and compactness of composition operators $C_{\varphi}$ acting on $\mathcal{Q}_K$-type spaces and $\mathcal{Q}_s$ spaces is characterized in terms of the norms of ${\varphi}^n$. Thus the author announces a solution to the problem raised by Wulan, Zheng and Zhou.

• 한국분말재료학회지
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• 제22권3호
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• pp.175-180
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• 2015

In this study, ternary compound Max Phase $Ti_2AlC$ material was mixed by 3D ball milling as a function of ball milling time. More than 99.5 wt% pure $Ti_2AlC$ was synthesized by using spark plasma sintering method at 1000, 1100, 1200, and $1300^{\circ}C$ for 60 min. The material characteristics of synthesized samples were examined with relative density, hardness, and electrical conductivity as a function of sintering temperature. The phase composition of bulk was identified by X-ray diffraction. On the basis of FE-SEM result, a terraced structures which consists of several laminated layers were observed. And $Ti_2AlC$ bulk material obtained a vickers hardness of 5.1 GPa at the sintering temperature of $1100^{\circ}C$.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권12호
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• pp.5103-5115
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• 2015

In radar imaging, a target is usually consisted of a few strong scatterers which are sparsely distributed. In this paper, an improved sparse signal recovery algorithm based on smoothed l₀ (SL0) norm method is proposed to achieve high resolution ISAR imaging with limited pulse numbers. Firstly, one new smoothed function is proposed to approximate the l₀ norm to measure the sparsity. Then a single loop step is used instead of two loop layers in SL0 method which increases the searching density of variable parameter to ensure the recovery accuracy without increasing computation amount, the cost function is undated in every loop for the next loop until the termination is satisfied. Finally, the new set of solution is projected into the feasible set. Simulation results show that the proposed algorithm is superior to the several popular methods both in terms of the reconstruction performance and computation time. Real data ISAR imaging obtained by the proposed algorithm is competitive to several other methods.

• 한국전기전자재료학회논문지
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• 제27권10호
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• pp.630-634
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• 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
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• 제25권1호
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• pp.36-42
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• 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
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• 제25권1호
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• pp.36-42
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• 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
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.169-172
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• 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.

• 대한수학회지
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• 제38권2호
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• pp.311-319
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• 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).