• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권6호
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• pp.1101-1112
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• 2011

The Multiuser Eigenmode Transmission (MET) has generated significant interests in literature due to its optimal performance in linear precoding systems. The MET can simultaneously transmit several spatial multiplexing eigenmodes to multiple users which significantly enhance the system performance. The maximum number of users that can be served simultaneously is limited due to the constraints on the number antennas, and thus an appropriate user selection is critical to the MET system. Various algorithms have been developed in previous works such as the enumerative search algorithm. However, the high complexities of these algorithms impede their applications in practice. In this paper, motivated by the necessity of an efficient and effective user selection algorithm, a low complexity recursive user selection algorithm is proposed for the MET system. In addition, the fairness of the MET system is improved by using the combination of the proposed user selection algorithm and the adaptive Proportional Fair Scheduling (PFS) algorithm. Extensive simulations are implemented to verify the efficiency and effectiveness of the proposed algorithm.

• Journal of the Optical Society of Korea
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• 제8권3호
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• pp.137-146
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• 2004

A new method of obtaining the eigenmode of an anisotropic planar waveguide is studied. The planar waveguide can be composed of an arbitrary number of isotropic or uniaxially anisotropic layers, provided all the optical axes arc lying in the incidence plane. Since the equation of motion for the TE mode is not different from that for the TE mode in an isotropic planar waveguide, only the equation of motion for the TM mode is of any concern. For this kind of device structure, the Maxwell's equations can be solved for one component of the electric field and one component of the magnetic field. The resulting coupled set of equations is linear in the propagation constant and the eigenmode can be easily obtained using canned numerical routines.

• 한국광학회:학술대회논문집
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• 한국광학회 2004년도 제15회 정기총회 및 동계학술발표회
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• pp.112-113
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• 2004

• 한국항행학회논문지
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• 제13권5호
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• pp.736-741
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• 2009

본 논문은 분할된 선형배열안테나를 사용하는 다중 사용자 MIMO 기술에서 코드북(codebook)을 운용 환경에 따라 최적화 하는 기술을 제안한다. 제안하는 기술은 공간상관도가 없는 MIMO 채널을 가정하여 디자인된 코드북을 각 순방향 링크의 송신 공간상관행렬을 이용하여 컬러링(coloring)하는 기술이며, 이를 위해 필요한 각 링크의 송신 상관행렬을 제한된 양의 long-term 피드백을 통해 피드백하는 기술을 제안한다. Zero-forcing maximum eigenmode transmission 기술을 사용하는 다중 사용자 MIMO 시스템에서, 제안하는 코드북 최적화 기술의 성능을 분석하였으며, 제안하는 기술이 적은양의 추가 피드백 정보량으로 다양한 운용 환경에 적응적으로 코드북을 최적화함을 보인다.

• Architectural research
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• 제14권1호
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• pp.27-33
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• 2012

This study proposes analytical methods to establish the eigenfunction of continuous system due to substructuring and decoupling of discrete subsystems. The dynamic characteristics of updated continuous system are evaluated by the constraint effect of consistent deformation at the interfaces between two systems. Beginning with the dynamic equation for constrained discrete system, this work estimates the modal eigenmode function for the continuous system due to the addition or deletion of discrete systems. Numerical applications illustrate the validity and applicability of the proposed method.

• Steel and Composite Structures
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• 제4권6호
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• pp.471-487
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• 2004

Modular steel scaffolds are commonly used as supporting scaffolds in building construction, and traditionally, the load carrying capacities of these scaffolds are obtained from limited full-scale tests with little rational design. Structural failure of these scaffolds occurs from time to time due to inadequate design, poor installation and over-loads on sites. In general, multi-storey modular steel scaffolds are very slender structures which exhibit significant non-linear behaviour. Hence, secondary moments due to both $P-{\delta}$ and $P-{\Delta}$ effects should be properly accounted for in the non-linear analyses. Moreover, while the structural behaviour of these scaffolds is known to be very sensitive to the types and the magnitudes of restraints provided from attached members and supports, yet it is always difficult to quantify these restraints in either test or practical conditions. The problem is further complicated due to the presence of initial geometrical imperfections in the scaffolds, including both member out-of-straightness and storey out-of-plumbness, and hence, initial geometrical imperfections should be carefully incorporated. This paper presents an extensive numerical study on three different approaches in analyzing and designing multi-storey modular steel scaffolds, namely, a) Eigenmode Imperfection Approach, b) Notional Load Approach, and c) Critical Load Approach. It should be noted that the three approaches adopt different ways to allow for the non-linear behaviour of the scaffolds in the presence of initial geometrical imperfections. Moreover, their suitability and accuracy in predicting the structural behaviour of modular steel scaffolds are discussed and compared thoroughly. The study aims to develop a simplified and yet reliable design approach for safe prediction on the load carrying capacities of multi-storey modular steel scaffolds, so that engineers can ensure safe and effective use of these scaffolds in building construction.

• Nuclear Engineering and Technology
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• 제55권1호
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• pp.310-323
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• 2023

The k-eigenvalue neutronics/thermal-hydraulics coupling calculation is a key issue for reactor design and analysis. Jacobian-free Newton-Krylov (JFNK) method, featured with super-linear convergence rate and high efficiency, has been attracting more and more attention to solve the multi-physics coupling problem. However, it may converge to the high-order eigenmode because of the multiple solutions nature of the k-eigenvalue form of multi-physics coupling issue. Based on our previous work, a modified JFNK with a line search method is proposed in this work, which can find the fundamental eigenmode together with thermal-hydraulics feedback in a wide range of initial values. In detail, the existing modified JFNK method is combined with the line search strategy, so that the intermediate iterative solution can avoid a sudden divergence and be adjusted into a convergence basin smoothly. Two simplified 2-D homogeneous reactor models, a PWR model, and an HTR model, are utilized to evaluate the performance of the newly proposed JFNK method. The results show that the performance of this proposed JFNK is more robust than the existing JFNK-based methods.

• Structural Engineering and Mechanics
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• 제12권2호
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• pp.215-230
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• 2001

In this paper, an asymptotic two-scale method is developed for solving vibration problem of long periodic structures. Such eigenmodes appear as a slow modulations of a periodic one. For those, the present method splits the vibration problem into two small problems at each order. The first one is a periodic problem and is posed on a few basic cells. The second is an amplitude equation to be satisfied by the envelope of the eigenmode. In this way, one can avoid the discretisation of the whole structure. Applying the Floquet method, the boundary conditions of the global problem are determined for any order of the asymptotic expansions.

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.449-450
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• 2009

위그너 분포 함수 측정을 통하여 진행하는 laser beam의 상관함수와 진행 특성들을 연구하였다. 위그너 분포 함수는 진행하는 laser beam의 total degree of coherence, beam quality parameter, 그리고 근접장 및 원거리장의 정보들을 보여준다. 위그너 분포 함수를 이용하여 공간상관 함수와 방향상관 함수를 구할 수 있으며, 이를 Schmidt mode decomposition을 이용하여 분석하면 laser beam의 보다 여러가지 특성들을 분석 할 수 있다. 이렇게 분석된 eigenmode들은 진행하는 laser beam의 보다 정확한 coherence 특성을 이해하게 해준다.

• Wind and Structures
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• 제21권6호
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• pp.641-656
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• 2015

Using large monopod bucket foundations as an alternative to monopiles for offshore wind turbines offers the potential for large cost savings compared to typical piled foundations. In this paper, numerical simulations are carried out to assess the risk of structural buckling during installation of large-diameter bucket foundations. Since shell structures are generally sensitive to initially imperfect geometries, eigenmode-affine imperfections are introduced in a nonlinear finite-element analysis. The influence of modelling the real lid structure compared to classic boundary conditions is investigated. The effects of including soil restraint and soil-structure interaction on the buckling analysis are also addressed.