• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.3
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• pp.535-544
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• 2023

In this paper, we study the effect of gradient vector calculation method(analytical method, central finite difference method) on adaptive beamforming to control weight distribution during iterated calculation when LMS algorithm (repeating method) is used to realize desired beam pattern. To this end, a quasi-ideal beam having an arbitrarily set beam width, a rotating beam, and a multi-beam were reviewed as examples. Numerical experiments applied the step parameters of the appropriate values to the adaptive beamforming system through trial and error equally to the two calculations, and compared the convergence characteristics of objective functions that evaluate adaptability and error using two methods for calculating gradient vectors.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.347-350
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• 2004

In this paper, the acceleration is studied for the rigid-plastic FEM of metal forming simulation. In the FEM, the direct iteration and Newton-Raphson iteration are applied to obtain the initial solution and accurate solution respectively. In general, the acceleration scheme for the direct iteration is not used. In this paper, an Aitken accelerator is applied to the direct iteration. In the modified Newton-Raphson iteration, the step length or the deceleration coefficient is used for the fast and robust convergence. The step length can be determined by using the accelerator. The numerical experiments have been performed for the comparisons. The faster convergence is obtained with the acceleration in the direct and Newton-Raphson iterations.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.48-51
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• 2010

본 논문에서는 자유경계문제 해석을 위해 정확도가 향상된 implicit 이동최소제곱 차분법을 제시한다. 계면경계에 대한 implicit 정의로 인해 비선형 시스템이 구성되고, 매 해석단계마다 절점해와 계면경계의 위치를 반복계산을 통해 찾는다. 계면경계 결정시 속도항을 한 단계 뒤로 지연시켜 explicit하게 근사적으로 계산하던 기존 방법에 비해 계면경계의 위치를 더 정확하게 계산할 수 있고, 결과적으로 해의 정확도가 향상되었다. 계면경계 위치값이 비교적 빠른 속도로 수렴하기 때문에 많은 반복계산이 필요치 않다. 수치예제를 통해 기존의 방법으로 계산한 결과와 비교하여 새롭게 개발한 implicit 방법의 향상된 정확도를 보였다.

• Korean Journal of Materials Research
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• v.8 no.1
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• pp.45-51
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• 1998

Ti-45at%AI-1.6at%Mn 조성을 갖는 금속간화합물의 장시간 및 반복산화 거동을조사하기 위하여 반응소결법 및 플라즈마 아크 용해법으로 제조한 시편에 대하여 80$0^{\circ}C$에서는 반응소결재와 용제재 모두 등온 및 반복산화에 대하여 우수한 저항성을 나타내었다. 90$0^{\circ}C$에서는 반응소결재의 경우에는 등온 및 반복산화에 대하여 우수한 저항성을 보였으며, 중량변화와 산화피막의 박리는 극히 적었다. 이에 비해 용제재의 경우에는 등온 및 반복산화에 의해 중향이 크게 변하였으며 피막의 박리도 극심하였다. 90$0^{\circ}C$에 있어서 두 재료간의 이러한 산화거동 차이는 기지/산화물 계면 부근에 형성된 산화층의 차이에 기인하는 것으로 간주하였다. 반응소결재의 경우에는 계면 부근에 연속적인 AO$_{3}$O$_{3}$층이 형성되며, 이러한 층이 산화에 대한 보호막으로 작용하는데 비하여 용제재에 있어서는 계면 부근에 AO$_{3}$O$_{3}$와 TiO$_{2}$의 혼합층이 형성되었다. 용제재의 반복산화시에 보여진 피막의 박리는 냉각시에 TiO$_{2}$와 기지간의 열팽창계수 차이에 기인하여 발생하는 열응력을 TiO$_{2}$가 견디지 못하고 박리를 초래한 것으로 해석하였다.

• Proceedings of the Korea Contents Association Conference
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• 2003.05a
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• pp.403-405
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• 2003

An iterative Green's function method (IGFM) is introduced to analyze complex electromagnetic waveguide structures in view of the university student. The IGFM utilizes the Green's function and iteration scheme. The physical mechanism with simple mathematical equations is used to formulate the IGFM. Scattering characteristics of a standard E-plane T-junction in a parallel-plate waveguide are theoretically investigated in terms of the IGFM. Numerical computations illustrate the characteristics of resection and transmission powers versus frequency. A dominant-mode solution is presented and compared with the higher-mode solutions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.6
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• pp.396-401
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• 1986

The method of steepest descent is applied to the analysis of electrostatic problems. The differences between iterative method and direct method, e.g. the method of moments, are not lined. It is shown that this method converges monotonically to the exact solution and is suitable for solving a problem of large system. Numerical results are presented for electrostatic case which show a good agreement with momet solution.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.1
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• pp.26-32
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• 2015

Purpose: The main purpose of this study is to suggest application plan of dipping method by comparing & analysing the difference between addition method and dipping method in the manufacture of metal-ceramic substructure of maxillary central incisor (#1), followed by assessing the work efficiency. Materials and Methods: Master die and hard plaster-copied one were produced and then a total of 20 copies, 10 copies for each through addition method and dipping method, were manufactured and experimented. Copings were fixed on the abutment model and invested in epoxy mounting cup. Samples were cut in labial and lingual direction, using cutter and then rubbed on sandpaper, whose 4 points were measured by using digital microscope. Results: The comparison of mean values by using t-test, parametric statistical method, shows overall significant difference (P < 0.05). Conclusion: The result of this study can be suggested as an application plan, since there is no significant difference between addition method and dipping method in the manufacture of metal-ceramic substructure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.11
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• pp.1039-1048
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• 2008

new computational procedure for the Non-Linear Vortex Lattice Method (NLVLM) is suggested in this work. Conventional procedures suggested so far usually involves inner iteration loop to update free vortex shape and an under-relaxation based iteration loop to determine the free vortex shape. In this present work, we suggest a new formula based on quasi-steady concept to fix free vortex shape which eliminates the need for inner iteration loop. Further, the ensemble averaging of the induced velocities for a given free vortex segment evaluated at each iteration significantly improves the convergence property of the algorithm without resorting to the under-relaxation technique. Numerical experiments over several low aspect ratio wings are carried out to obtain optimal empirical parameters such as the length of the free vortex segment, the vortex core radius, and the rolled-up wake length.

• Tunnel and Underground Space
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• v.27 no.3
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• pp.172-184
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• 2017

The hardness and mechanical properties of the minerals in the Daejeon granite according to depths were investigated by indentation test, load-unload test, and cycle test of dynamic ultra-micro hardness. As a result of the tests, it was possible to classify into three mineral groups (Group-1, -2, -3). The Martens hardness was not significantly different between 41 m and 223 m depths in three mode tests. Nevertheless, they showed in the order of a cycle test < load-unload test < indentation test. Considering the average Martens hardness, elastic modulus, and indentation work for each mineral group, their boundaries were relatively clear. In conclusion, A relatively accurate hardness of minerals can be obtained by three mode tests of dynamic ultra-micro hardness. In addtion, it was possible to characterize the elastic modulus and the elastic-plastic properties of the minerals from the load-unload and cycle tests.

• The Korean Journal of Applied Statistics
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• v.30 no.2
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• pp.291-299
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• 2017

Mack and Skillings (1980) proposed nonparametric procedures in a randomized block design with replications as general alternatives. This method is used to find the difference in the treatment effect; however, it can cause a loss of inter block information using the ranking in each block. In this paper, we proposed new nonparametric procedures in a randomized block design with replications using an aligned method proposed by Hodges and Lehmann (1962) that used information of blocks and based on the joint placement suggest by Chung and Kim (2008). We also compared the power of the test of the proposed procedures and established a method through Monte Carlo simulation.