• Journal of the Korean Magnetics Society
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• v.18 no.5
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• pp.163-167
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• 2008

The electronic structure and magnetism of superlattice systems consisted of Heusler compound $Co_2MnSi$ (CMS) and zinc-blende MnAs (MA) are investigated by means of the all-electron full potential linearized augmented plane wave method within the generalized gradient approximation. Four superlattice systems are considered, that is CMS(m)/MA(n), where m and n, being either 2 or 4, denote the number of alternatingly arrayed layers of the compounds in a superlattice along [001] direction. From the calculated total magnetic moments as well as the total density of states, it is found that neither of the four systems is half-metallic. It is also found that the Mn atoms are antiferromagnetically coupled in the systems of CMS2/MA2 and CMS2/MA4. The total and atom-resolved density of states of the four superlattices are compared with those of the bulk $Co_2MnSi$ and MnAs, and the influences of the change in the systems symmetry on the magnetism and half-metallicity are discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.174-177
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• 2001

The electron transport coefficients, the electron drift velocity W, the longitudinal diffusion coefficient $ND_L$ and $D_L/{\mu}$, in pure Xe were calculated over the wide E/N range from 0.01 to 500 Td at 1 Torr by two-term approximation of the Boltzmann equation for determination of electron collision cross sections set and for quantitative characteristic analysis of Xe molecular gas.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.2
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• pp.112-126
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• 2010

시계열데이터는 ARMA 분석에 적합지 않은 요소를 내재하고 있는 경우가 있다. 특히 선형성과 주기성을 가진 요소가 확률적인 분포와 자주 혼재되어 있다. 이 논문에서는 이런 선형적 주기적 요소를 찾아내고 분석하는 방법을 제시한다. 특히 주기적 요소는 여러 주기가 층층이 겹쳐져서 나타난다. 주기 간에는 서로 일정 정수비율을 유지하며, 한 주거 안에 다른 주기가 내포되어 있는 경우(nested periods)가 많다. 시간규모(time-scale)개념을 도입하여 이러한 주기적 요소를 개념적으로 정립하고자 했다. 선형적 요소와 주기적 요소가 제거된 후 추출된 데이터는 MA-approximation이라는 방법을 사용하여 가장 데이터에 근접한 ARMA 모텔을 찾아낸다. 마지막으로 선형적 주기적 요소와 ARMA 추정결과를 종합하여 control boundary를 결정하는 방법을 제시한다.

• Structural Engineering and Mechanics
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• v.54 no.3
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• pp.393-417
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• 2015

In this paper an 8-node quadrilateral assumed stress hybrid Mindlin plate element with $39{\beta}$ is presented. The formulation is based on complementary energy principle. The proposed element is free of shear locking and is capable of passing all the patch tests, especially the non-zero constant shear enhanced patch test. To accomplish this purpose, special attention is devoted to selecting boundary displacement interpolation and stress approximation in domain. The arbitrary order Timoshenko beam function is successfully used to derive the boundary displacement interpolation. According to the equilibrium equations, an appropriate stress approximation is rationally derived. Particularly, in order to improve element's accuracy, the assumed stress field is derived by employing $39{\beta}$ rather than conventional $21{\beta}$. The resulting element can be adopted to analyze both moderately thick and thin plates, and the convergence for the very thin case can be ensured theoretically. Excellent element performance is demonstrated by a wide of experimental evaluations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.11
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• pp.3204-3217
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• 2023

In this paper, the downlink of the multicast based spatial modulation systems is investigated. Specifically, physical layer multicasting is introduced to increase the number of access users and to improve the communication rate of the spatial modulation system in which only single radio frequency chain is activated in each transmission. To minimize the bit error rate (BER) of the multicast based spatial modulation system, a joint optimizing algorithm of antenna selection and multicast precoding is proposed. Firstly, the joint optimization is transformed into a mixed-integer non-linear program based on single-stage reformulation. Then, a novel iterative algorithm based on the idea of branch and bound is proposed to obtain the quasioptimal solution. Furthermore, in order to balance the performance and time complexity, a low-complexity deflation algorithm based on the successive convex approximation is proposed which can obtain a sub-optimal solution. Finally, numerical results are showed that the convergence of our proposed iterative algorithm is between 10 and 15 iterations and the signal-to-noise-ratio (SNR) of the iterative algorithm is 1-2dB lower than the exhaustive search based algorithm under the same BER accuracy conditions.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2785-2796
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• 2023

How to generate the precise broad group cross section is important for the fast reactor design. In this study, a fast reactor multi-group cross-section generation code MGGC2.0 are developed in-house for processing ultrafine group MATXS format library. Validation and verification are performed for MGGC2.0 code by applying the benchmarks of ICSBEP handbook, and the results of MGGC2.0 agree well with that of MCNP. The consistent P_N method with critical buckling search is in good agreement that condensed with TWODANT flux and flux moment for the inner core and outer core region. For the radial blanket and reflector, two region approximation method has been applied in MGGC2.0 by using collision Probability Method neutron flux solver. The RBEC-M benchmark was used to verify the power distribution calculation, and the relative error of power distribution comparison with the reference are less than 0.8% in the fuel region and the maximum relative error is 5.58% in the reflector region. Therefore, the precise broad cross section can be generated by MGGC2.0 for fast reactor.

• ETRI Journal
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• v.35 no.5
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• pp.931-934
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• 2013

The weight calculation in an iterative algorithm is the most computationally costly task in computed tomography image reconstruction. In this letter, a fast algorithm to speed up the weight calculation is proposed. The classic square pixel rotation approximate calculation method for computing the weights in the iterative algorithm is first analyzed and then improved by replacing the square pixel model with a circular pixel model and the square rotation approximation with a segmentation method of a circular area. Software simulation and hardware implementation results show that our proposed scheme can not only improve the definition of the reconstructed image but also accelerate the reconstruction.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.4
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• pp.481-488
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• 1999

A thermal model based on the chamber geometry of the industry-standard AST SHS200MA rapid thermal processing system has been developed for the study of thermal uniformity and process repeatability thermal model combines radiation energy transfer directly from the tungsten-halogen lamps and the steady-state thermal conducting equations. Because of the difficulties of solving partial differential equation, calculation of wafer temperature was performed by using finite-difference approximation. The proposed thermal model was verified via titanium silicidation experiments. As a result, we can conclude that the thermal model show good estimation of wafer surface temperature distribution.

• Journal of the Korean Ceramic Society
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• v.35 no.12
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• pp.1337-1342
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• 1998

To investigate an effect of phase separation on precipitation characteristics of ZnS microcrystals in ma-trix glass ZnS doped borosilicate glasses for nonlinear optical applications were prepared by melting and pre-cipitation process. ZnS dopant contributed to phase separation promotion which increased the phase separa-tion of the matrix glass within immiscibility region. It was also found that ZnS as phase separation promoter showed a similar contribution for some selected glass compositions in miscibility region. The precipitation of ZnS microcrystals occurred in thephase separable glass compoitions. The radius of ZnS microcrystals in-creased with increasing the heat treatment temperature and Na2O contents of matrix glass composition. The ZnS particle sizes estimated by effective mass approximation ranged from about 30 to 80${\AA}$ It was suf-ficiently small to show quantum confinement effect.

• Journal of Ship and Ocean Technology
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• v.4 no.2
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• pp.1-12
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• 2000

The present study concentrates on the weak-scatterer hypothesis for the nonlinear wave-body interaction problems. In this method, the free surface boundary conditions are linearized on the incoming wave profile and the exact body motion is applied. The considered problems are the diffraction problem near a circular cylinder and the ship response in oblique waves. The numerical method of solution is a Rankine panel method. The Rankine panel method of this study adopts the higher-order B spline basis function for the approximation of physical variables. A modified Euler scheme is applied for the time stepping, which has neutral stability. The computational result shows some nonlinear behaviors of disturbance waves and wave forces. Moreover, the ship response shows very close results to experimental data.