Improved efficient bounding method for DC contingency analysis using reciprocity properties

Optimal analysis for optimal design of cyclic symmetric structures subject to frequency constraints

An efficient contingency evaluation method for power system security analysis

본 논문은 유한 차분 시간 영역(FDTD: Finite-Difference Time-Domain)법을 이용하여 낙뢰에 노출된 항공기와 같이 높은 도전성 물질로 구성된 구조체의 간접적 영향 분석을 위한 전자파 해석기법 연구를 수행하였다. 간접적 영향 분석을 위해 사용되는 낙뢰 파형은 매우 낮은 주파수 특성을 가지며, 알루미늄과 탄소섬유복합물질과 같이 높은 도전성 물질들로 구성된 구조체는 매우 짧은 표피 깊이를 가지고 있기 때문에 일반적인 3차원 FDTD법을 이용하여 해석을 수행할 경우, 매우 많은 메모리와 해석시간이 요구된다. 본 연구팀에서는 낙뢰 특성과 높은 도전율을 갖는 구조에 적합한 전자파 해석기법을 개발하였다. 개발된 해석 기법은 2차원 FDTD와 INBC(Impedance Network Boundary Condition) 알고리즘을 적용하였으며, 개발된 해석기법을 이용하여 낙뢰에 노출된 구조체의 간접적 영향을 분석하였다. We perform a electromagnetic analysis method for indirect effects of a high-conductive structure such as an aircraft exposed by lightning, by using the finite-difference time-domain(FDTD) method. The lightning waveform used to analyze indirect effects has low frequency spectrum and high-conductive materials such as aluminum and carbon fiber composite materials have very short skin depths, and thus, it requires large memory and long computation time using conventional three dimensional FDTD analysis method. We develop an efficient electromagnetic analysis method suitable for lightning and high-conductive structures. The developed analysis method is based on two dimensional FDTD and impedance network boundary condition(INBC) algorithms and we investigate the indirect effects on the structures exposed to lightning.

Efficient universal method for numerical analysis of slotted cavities used in different gyrodevices is proposed. It can be useful both for incorporation in different computer codes to simulate gyrodevice operation and for detailed investigations of different aspects concerning their basic physics.

Large deflection distributed plasticity analysis of 3D steel frameworks

Yield has always been a driving consideration during fabrication of modern semiconductor industry. Statistically, the largest portion of wafer yield loss is defective scan failure. This paper presents efficient failure analysis methods for initial yield ramp up and ongoing product with scan diagnosis. Result of our analysis shows that more than 60% of the scan failure dies fall into the category of shift mode in the very deep submicron (VDSM) devices. However, localization of scan shift mode failure is very difficult in comparison to capture mode failure because it is caused by the malfunction of scan chain. Addressing the biggest challenge, we propose the most suitable analysis method according to scan failure mode (capture / shift) for yield enhancement. In the event of capture failure mode, this paper describes the method that integrates scan diagnosis flow and backside probing technology to obtain more accurate candidates. We also describe several unique techniques, such as bulk back-grinding solution, efficient backside probing and signal analysis method. Lastly, we introduce blocked chain analysis algorithm for efficient analysis of shift failure mode. In this paper, we contribute to enhancement of the yield as a result of the combination of two methods. We confirm the failure candidates with physical failure analysis (PFA) method. The direct feedback of the defective visualization is useful to mass-produce devices in a shorter time. The experimental data on mass products show that our method produces average reduction by 13.7% in defective SCAN & SRAM-BIST failure rates and by 18.2% in wafer yield rates.

This paper presents an efficient numerical method for the harmonic analysis of viscoelastically damped structural systems characterized by a frequency‐dependent structural damping matrix, making use of the complex mode superposition method. Departing from the undamped eigensolution, the proposed numerical method updates the complex and frequency‐dependent eigenpair avoiding the solution of a complex eigenproblem for each computational frequency. The complex eigenvalues and eigenvectors are updated within the desired tolerance by an adaptive step‐size control scheme using the first‐ and higher order eigenderivatives. The influence on the computation time of the considered number of eigenderivatives and the tolerance is discussed, and the efficiency of the proposed numerical method for the harmonic analysis of viscoelastically damped large‐ordered structural systems is proved. Finally, a practical application is presented where the harmonic response of a constrained layer damping cantilever beam subjected to a base motion is analyzed. The complex and frequency‐dependent eigenvalues and eigenvectors are computed, the modal contributions to the total response are determined, and the total response is approximated by the complex mode superposition method. Finally, the approximated response is validated with the exact one computed by the direct frequency method and with that experimentally measured. Copyright © 2011 John Wiley & Sons, Ltd.

Electrical impedance tomography (EIT) is an inverse imaging technique used to reconstruct resistive distributions. Some EIT inverse methods, such as the Gauss-Newton method, use the finite element method in the forward problem to solve for the Jacobian matrix. The authors detail methods to improve the solution time in the forward problem and accurate Jacobian calculation. The first suggestion is to keep the same node grounded for all projection angles by floating the current source. Details of an optimised Jacobian formation are also presented including full exploitation by sparse vector methods. The application of EIT to interface pressure distribution measurements makes use of a pressure sensitive resistive mat that can be cut to any shape or size. This flexibility can be taken advantage of and a square or rectangular domain comprising square bilinear elements is chosen. The sparse matrix nested dissection node renumbering algorithm then gives further speed advantages and also enables best optimisation with sparse vector techniques.

A practical and efficient coupling method for large scale soil–structure interaction problems

A consistent and efficient graphical analysis method to improve the quantification of reversible tracer binding in radioligand receptor dynamic PET studies

Precise simulation of magnetic field in the air gap is necessary to Predict of electromagnetic performance of permanent magnet machines. In this paper an analytical approach is proposed to calculate the magnetic field of slot-less Axial flux permanent magnet machine. Finite element method is the most precise method for magnetic calculation in the air gap although because of its low speed calculation is not appropriate for parametric and optimization studies. In this paper, an efficient analytical method is used to parametric studies on magnetic field in the air gap in case of no-load operation. By applying above mentioned method with high analytical speed, flux density in the middle of air gap is predicted and then induced voltage is calculated. Result of proposed analytical method is compared with 3-D FEM simulations that are reached from Ansys-Electronics software. These results are in the form of Quasi-3D.

While vitamin D3 is recognized as a neuroactive steroid affecting both brain development and function, efficient analytical method in determining vitamin D3 metabolites in the brain tissue is still lacking, and the relationship of vitamin D3 status between serum and brain remains elusive. Therefore, we developed a novel analysis method by using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to simultaneously quantify the concentrations of 25-hydroxyvitamin D3 (25(OH)D3) and 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) in the serum and brain of rats fed with different dose of vitamin D3. We further investigated whether variations of serum vitamin D3 metabolites could affect vitamin D3 metabolite levels in the brain. Serum and brain tissue were analyzed by HPLC-MS/MS with electrospray ionization following derivatization with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD). The method is highly sensitive, specific, and accurate to quantify 25(OH)D3 and 24,25(OH)2D3 in animal brain tissue. Vitamin D3 metabolites in brain tissue were significantly lower in rats fed with a vitamin D deficiency diet than in rats fed with high vitamin D3 diet. There was also a strong correlation of vitamin D3 metabolites in serum and brain. These results indicate that vitamin D3 status in serum affects bioavailability of vitamin D3 metabolites in the brain.

Plane‐wave scattering by metallic grating with artificial anisotropic substrate is a problem solved in this study for the design of broadband reflectarrays. For determination of the reflection characteristics of such structures, a generalised transmission line modelling is used for evaluating the dyadic Green's function. This function is utilised in a summation equation used for calculating the induced electric currents on the reflectarray's metallic grating. For solving the obtained summation equation, the Periodic Method of Moments with Galerkin procedure is applied. Such an analysis method helps to compute the phase diagram needed to design of reflectarray. The efficiency of this method is assessed by considering its cost‐time and rate of convergence versus space harmonics. In the design step, a new phase realisation approach is implemented for minimising the frequency dispersion's adverse effects. This approach optimises the arrangement of metallic elements on the reflectarray's aperture and decreases the dependency of broadband reflectarray design to the element phase behaviour. As a result, this technique leads to lower side lobe level and better frequency response than traditional approaches. To verify the results of the developed solution, two different broadband reflectarrays for X‐ and Ku‐bands are fabricated and measured.

Sleep Apnea Syndrome (SAS) has attracted considerable attention in recent years because it is known to cause catastrophes when people suffering from it fall asleep while driving. In addition, approximately 70% of SAS patients have other lifestyle-related diseases, which are further complicated owing to SAS; therefore, its early detection is important. Moreover, the detection of pre-SAS, which is likely to turn into SAS in the future, may help in the early detection of SAS. In this study, a method to identify SAS and pre-SAS using only sound data has been proposed. In the proposed method, peculiar breathing sound patterns in SAS are analyzed using the k-means clustering method and perform discriminant analysis using quantification theory based on the results. Because respiratory sound data is extensive and non-uniform during sleep, an efficient analysis method is required. The presented analysis method focuses on the features of SAS sounds, and performs the analysis almost automatically; therefore, the time required for analysis is reduced and the uniformity of the analysis results is guaranteed. Using this method, it is possible to distinguish between non-SAS and SAS symptoms including pre-SAS symptoms, which is difficult to perform using the Apnea-Hypopnea Index, which is a measure of SAS that employs breathing sound data only. Thus, this method, which also analyzes pre-SAS, is convenient for the early detection and treatment of SAS and can also be expected to contribute toward the early detection of preliminary lifestyle-related diseases.

Harmonic Balance is nowadays the most efficient method for the periodic steady state analysis of microwave circuits. Unfortunately this method cannot conveniently handle realistic wide band input signals, because its computation time grows rapidly with the number of harmonics. A new method is proposed which resolves the above mentioned limitation of the Harmonic Balance. A substantial computation time saving is obtained with respect to the Harmonic Balance.