http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
최봉열 경북대학교 전자기술연구소 1987 電子技術硏究誌 Vol.8 No.1
A criterion is developed to determine the order of the reduced-order system based upon Davison's simplification technique using the values of the simallest eigenvalue neglected and the largest eigenvalue retained in the model.
Lyapunov 해석기법을 이용한 규정된 영역 내로의 극점배치 견실성 해석
최봉열 경북대학교 전자기술연구소 1996 電子技術硏究誌 Vol.17 No.2
In this paper, we consider the pole assignment robustness problem of a perturbed system represented by a state space model. Based upon the Lyapunov approach, a bound on the highly structured perturbation is obtained for the eigenvalues of a perturbed matrix to be located in a specified region. The resulting bound is shown to be less conservative than the previous ones. Specially, for the case of the hermitian matrix, the bound is obtained in terms of the nominal matrix without solving the Lyapunov equation. To verify the effectiveness of the proposed approach, several examples ate shown.
흉부 Phantom을 이용한 Chest PA검사에서 자동 노출방식의 Density와 Sensitivity 설정 값에 따른 영상 및 피폭선량에 대한 고찰
최봉열(Bong-Yeol Choi),정명진(Myung-Jin Jung):차장원(Jang-Won Cha),하종현(Jong-Hyeon Ha),김성희(Seong-Hee Kim):노지숙(Ji-Sook Nho) 대한영상의학기술학회 2016 대한영상의학기술학회 논문지 Vol.2016 No.1
목 적 : 자동노출제어장치를 사용하는 흉부 후전 검사는 density, sensitivity의 선택에 따라 환자가 받는 피폭선량과 영상의 질이 달라진다. 본 논문에서는 자동노출제어장치의 density, sensitivity의 선택에 따른 최적의 진단 영상을 획득하면서 피폭선량을 최소화하는 방안에 대해 연구하였다. 대상 및 방법 : 폐암 조직이 삽입 되어진 팬텀을 이용하여 PA 선자세( PA erect position)로 wall bucky에 고정하였고, 초점-필름간 거리(Focus-Film Distance, 이하 FFD) 180 cm, 조사야는 17 ×17 로하고 흉추6번 높이에 선속 중심을 맞춘 후, AEC mode에서 관전압은 120kV로 설정하였으며, Density, Sensitivity의 조건을 변화하면서 검사하였다. Density는 +3, 0, -3으로, Sensitivity는 s200, s400, s800으로 변화하면서 설정하였다. AEC mode의 Density, Sensitivity 변화에 따라 검사된 Chest PA 영상을 PACS 프로그램을 이용하여 근육(Muscle), 종괴(cancer), 뼈(bone)에 114㎟의 동일한 크기로 관심영역 (Region of interest, 이하 ROI)를 설정하여 신호 강도의 평균값(Average) 및 표준편차(SD)를 측정하였다. 이렇게 측정된 값을 가지고 대조도 대 잡음비(Contrast to Noise Ratio, 이하 CNR)과 신호대 잡음비(Signal to Noise Ratio, SNR)을 계산하여 영상을 비교하였고, DR System에서 산출된 dGy㎠값으로 피폭선량을 비교 하였다. 결 과 : 선량은 density값이 높고 sensitivity값이 낮을수록 많았고, density값이 낮고 sensitivity값이 높을수록 적게 측정되었으므로 선량측면에서는 density를 낮게, sensitivity 높게 설정함이 적합함을 알 수 있었다. CNR, SNR은 muscle, bone에서는 density, sensitivity의 변화에 따라 어느 정도 차이가 있었지만, cancer에서는 차이가 매우 적었다. 결 론 : 화질 측면에서 AEC mode의 density, sensitivity 변화는 크게 고려하지 않아도 된다고 생각 된다. 선량측면에서는 density를 낮게, sensitivity 높게 설정함이 적합하다. Chest PA검사 시 위와 같은 AEC 선택모드의 조합으로 피폭선량이 감소 될 것으로 기대된다. Purpose : Chest recession inspection using the automatic exposure control unit varies the radiation dose and image quality of patient receives, depending on the choice of density, sensitivity. In this paper, we study the ways to obtain optimal diagnostic images in accordance with the automatic exposure control unit density, choice of sensitivity while minimizing radiation exposure. Materials and Methods : And lung tissue was fixed using a phantom been inserted into the wall bucky stance PA (PA erect position), focus-film distance (Focus-Film Distance, below FFD) 180cm, josaya is 17 × 17 with the Align the flux centered on the Tspine 6 high in AEC mode tube voltage was set at 120kV, Density, the conditions of Sensitivity It was changed while test. Density is in the +3, 0, -3, Sensitivity was set and change as s200, s400, s800. A Chest PA imaging in accordance with the Density, Sensitivity change in AEC mode using the PACS program sets the ROI to the same size of the 114㎟ Muscle, cancer, bone and measure the Average and SD signal strength. This has the measured values were compared by calculating the SNR and CNR image, the exposure dose was compared to the value calculated in dGy㎠ DR System. Result : TFollowed by a high dose density value, the lower the value, sensitivity, low density value was found to measure because the less the higher the sensitivity value in terms of low dose density, high sensitivity settings are also suitable. CNR, SNR is muscle, bone although in a somewhat different according to the change of density, sensitivity, cancer, the difference is very small. Conclusion : Density, sensitivity changes in AEC mode in terms of quality do not think that is largely considered.In terms of low dose density, sensitivity settings are also highly suitable.Dose reduction is expected to be in the AEC mode, select a combination above Chest PA during inspection.
김봉석,최봉열,김경연 한국전기전자학회 2014 전기전자학회논문지 Vol.18 No.4
In stratified flows of two immiscible liquids, due to the vibration in a pipe, the shape of the interface is not always periodic and it causes the different end points of the interfacial boundary. In this case the performance is not good. To solve this, in this paper, the hybrid-type Fourier series is proposed, which consists of both the polynomial and the trigonometric terms. Under the stationary interfacial boundary during acquiring a full set of voltage data, the performance of the proposed method is evaluated through the numerical experiments. The results show that the proposed method performs better than the conventional Fourier series in estimating the interfacial boundary.
Directional Algebraic Reconstruction Technique for Electrical Impedance Tomography
김지훈,최봉열,Umer Zeeshan Ijaz,김봉석,김신,Kyung Youn Kim 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.4
We assume that the resistance matrix can be found in electrical impedance tomography (EIT) from the assumption of linear dependence between the voltages and the currents. With the help of the resistance matrix and the transfer impedance between the electrodes, a directional algebraic reconstruction technique (DART) is proposed for EIT. The goal is to reconstruct the resistivity distribution by weighting the matrices that are obtained by calculating the orthogonal distance of the underlying mesh elements from the neighboring port resistivity lines. These weighting matrices, which only depend on the topology of the underlying mesh, can be calculated offline and result in a computationally efficient online procedure with a reasonable image reconstruction performance. Simulation results are provided to validate this approach.