• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
• /
• pp.143-144
• /
• 2006

The recent power systems are very complex and to model them completely is impractical for analysis of electromagnetic transient Therefore areas outside the immediate area of interest must be represented by some form of Frequency Dependent Network Equivalent (FDNE). In this paper a method for developing Frequency Dependent Network Equivalent (FDNE) using S-domain rational Function Fitting is presented and demonstrated. The FDNE is generated by Linearized Least Squares Fitting(LSF) of the frequency response of a S-domain formulation. This Three-port FDNE have been applied to the test AC power system. The electromagnetic transient package PSCAD/EMTDC is used to assess the transient response of the Three-port FDNE developed under different condition. The study results have indicated the robustness and accuracy of Three-port FDNE for analisys of electromagnetic transient and harmonic assessment.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
• /
• pp.145-146
• /
• 2006

The recent power systems are very complex and to model them completely is impractical for analysis of electromagnetic transient. Therefore areas outside the immediate area of interest must be represented by some form of Frequency Dependent Network Equivalent (FDNE). In this paper a method for developing Frequency Dependent Network Equivalent (FDNE) using Z-domain rational Function Fitting is presented and demonstrated. The FDNE is generated by Linearized Least Squares Fitting(LSF) of the frequency response of a Z-domain formulation. This Three-port FDNE have been applied to the test AC power system. The electromagnetic transient package PSCAD/EMTDC is used to assess the transient response of the Three-port FDNE developed under different condition. The study results have indicated the robustness and accuracy of Three-port FDNE for analisys of electromagnetic transient and harmonic assessment.

• 대한방사선기술학회지:방사선기술과학
• /
• 제21권2호
• /
• pp.53-56
• /
• 1998

Highly sensitive $CaSO_4:Tm$ TLD is fabricated and their trap parameters are determined. The glow curve of $CaSO_4:Tm$ consists of three glow peaks and these peaks are isolated by the thermal bleaching method. The isolated glow peaks are fitted by a least squares method. The activation energies are 0.68, 0.82 and 1.03 eV. The frequency factors are $8.09{\times}10^8,\;9.14{\times}10^8$ and $1.03{\times}10^9/s$, and the kinetic orders are 1.37, 1.54 and 1.68, respectively. The optimum temperature range of the main peak for radiation dosimetry is between 220 and $290^{\circ}C$.

• 대한화학회지
• /
• 제51권5호
• /
• pp.407-411
• /
• 2007

크기 분포를 가진 금 나노 입자 콜로이드의 소광 스펙트럼을 미 이론으로 계산하고 실험과 비교하였다. 입자 크기 분포를 고려한 계산이 크기 분포를 고려하지 않은 계산보다 실험과 더 가까움을 확인하였다. 최소 자승법을 이용하여 실험에서 얻은 소광 스펙트럼으로부터 입자 크기 분포를 이론적으로 도출하였다. 이렇게 얻은 입자 크기는 입자 지름이 10에서 28 나노미터인 경우 투과전자현미경 분석 결과와 잘 일치하였다.

• The Journal of the Acoustical Society of Korea
• /
• 제25권4E호
• /
• pp.154-158
• /
• 2006

In this paper, we suggest a noise estimation method for speech enhancement in nonstationary noisy environments. The proposed method consists of the following two main processes. First, in order to receive fewer affect of variable signals, a best fitting regression line is used, which is obtained by applying a least squares method to coefficient magnitudes in a node with a uniform wavelet packet transform. Next, in order to update the noise estimation efficiently, a differential forgetting factor and a correlation coefficient per subband are used, where subband is employed for applying the weighted value according to the change of signals. In particular, this method has the ability to update the noise estimation by using the estimated noise at the previous frame only, without utilizing the statistical information of long past frames and explicit nonspeech frames by voice activity detector. In objective assessments, it was observed that the performance of the proposed method was better than that of the compared (minima controlled recursive averaging, weighted average) methods. Furthermore, the method showed a reliable result even at low SNR.

• Journal of Mechanical Science and Technology
• /
• 제18권12호
• /
• pp.2209-2215
• /
• 2004

In the present research work, an automated machine vision system and a new algorithm to interpret the inspection data has been developed. In the past, the control of tolerance of front-chassis-module was done manually. In the present work a machine vision system and required algorithm was developed to carryout dimensional evaluation automatically. The present system is used to verify whether the automobile front-chassis-module is within the tolerance limit or not. The directional ability parameters related with front-chassis-module such as camber, caster, toe and king-pin angle are also determined using the present algorithm. The above mentioned parameters are evaluated by the pose of interlinks in the assembly of an automobile front-chassis-module. The location of ball-joint center is important factor to determine these parameters. A method to determine the location of ball-joint center using geometric features is also suggested in this paper. In the present work a 3-D best fitting method is used for determining the relationship between nominal design coordinate system and the corresponding feature coordinate system.

• Journal of Radiation Protection and Research
• /
• 제45권4호
• /
• pp.171-177
• /
• 2020

Background: This study aims to determine the effective atomic number (Zeff) from dual-energy image sets obtained using a conventional computed tomography (CT) simulator. The estimated Zeff can be used for deriving the stopping power and material decomposition of CT images, thereby improving dose calculations in radiation therapy. Materials and Methods: An electron-density phantom was scanned using Philips Brilliance CT Big Bore at 80 and 140 kVp. The estimated Zeff values were compared with those obtained using the calibration phantom by applying the Rutherford, Schneider, and Joshi methods. The fitting parameters were optimized using the nonlinear least squares regression algorithm. The fitting curve and mass attenuation data were obtained from the National Institute of Standards and Technology. The fitting parameters obtained from stopping power and material decomposition of CT images, were validated by estimating the residual errors between the reference and calculated Zeff values. Next, the calculation accuracy of Zeff was evaluated by comparing the calculated values with the reference Zeff values of insert plugs. The exposure levels of patients under additional CT scanning at 80, 120, and 140 kVp were evaluated by measuring the weighted CT dose index (CTDIw). Results and Discussion: The residual errors of the fitting parameters were lower than 2%. The best and worst Zeff values were obtained using the Schneider and Joshi methods, respectively. The maximum differences between the reference and calculated values were 11.3% (for lung during inhalation), 4.7% (for adipose tissue), and 9.8% (for lung during inhalation) when applying the Rutherford, Schneider, and Joshi methods, respectively. Under dual-energy scanning (80 and 140 kVp), the patient exposure level was approximately twice that in general single-energy scanning (120 kVp). Conclusion: Zeff was calculated from two image sets scanned by conventional single-energy CT simulator. The results obtained using three different methods were compared. The Zeff calculation based on single-energy exhibited appropriate feasibility.

• 대한전자공학회논문지
• /
• 제10권6호
• /
• pp.45-55
• /
• 1973

본 논문은 한개의 터널다이오드로 구성된 시간에 무관한 비선형 회로를 논한다 부저항 소자로 구성된 비선형 회로의 해를 구하기 전에 비선형 소자의 정특성을 어떤 함수로 표시할 필요가 있다. 최소 자승법에 의해서 정특성을 표현하는 근사 다항식 커브를 구했다. 비선형 회로를 해석하기 위해서는 우선 그 회로에 관한 상태방정식이 설정되면 프레딕터·코렉터 방법에 의해서 해를 구할수 있다. 최종적으로, 비선형 회로의 안정도와 발진 조건을 논하기 위해서 limit cycle을 점철했다.

• 한국광학회지
• /
• 제8권4호
• /
• pp.267-276
• /
• 1997

서로 대칭되는 이중 조명을 이용한 홀로그래피 네파간섭계를 구성하여 횡변위와 종변위를 동시에 측정하였다. 물체파와 재생파의 간섭을 일으킨 후 위상이동법으로 변위위상도를 작성하였으며 최소제곱법맞춤으로 위상도의 잡음을 제거하였다. 이러한 방법으로 네파간섭계의 두 광로에 존재하는 위성의 차와 합에 대한 정보를 구하였으며, 파장 632.8 nm인 헬륨-네온 레이저 광선에 대하여 종변위와 횡변위는 각각 정밀도 .lambda./40 및 .lambda./100 이내로 측정되었다.

• 한국측량학회지
• /
• 제27권1호
• /
• pp.723-733
• /
• 2009

This study proposes a sequence of procedures to extract building boundaries and planar patches through segmentation of rasterized lidar data. Although previous approaches to building extraction have been shown satisfactory, there still exist needs to increase the degree of automation. The methodologies proposed in this study are as follows: Firstly, lidar data are rasterized into grid form in order to exploit its rapid access to neighboring elevations and image operations. Secondly, propagation of errors in raw data is taken into account for in assessing the quality of gradients-driven properties and further in choosing suitable parameters. Thirdly, extraction of planar patches is conducted through a sequence of processes: histogram analysis, least squares fitting, and region merging. Experimental results show that the geometric components of building models could be extracted by the proposed approach in a streamlined way.