• Wind and Structures
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• 제29권6호
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• pp.389-403
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• 2019

In this study, two original spectral representations of stationary stochastic fields, say the continuous proper orthogonal decomposition (CPOD) and the frequency-wavenumber spectral representation (FWSR), are derived from the Fourier-Stieltjes integral at first. Meanwhile, the relations between the above two representations are discussed detailedly. However, the most widely used conventional Monte Carlo schemes associated with the two representations still leave two difficulties unsolved, say the high dimension of random variables and the incompleteness of probability with respect to the generated sample functions of the stochastic fields. In view of this, a dimension-reduction model involving merely one elementary random variable with the representative points set owing assigned probabilities is proposed, realizing the refined description of probability characteristics for the stochastic fields by generating just several hundred representative samples with assigned probabilities. In addition, for the purpose of overcoming the defects of simulation efficiency and accuracy in the FWSR, an improved scheme of non-uniform wavenumber intervals is suggested. Finally, the Fast Fourier Transform (FFT) algorithm is adopted to further enhance the simulation efficiency of the horizontal stochastic wind velocity fields. Numerical examplesfully reveal the validity and superiorityof the proposed methods.

• 정보처리학회논문지A
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• 제16A권6호
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• pp.443-452
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• 2009

32비트 아키텍처가 현대 마이크로프로세서의 표준이 되어가고 있음에도 불구하고 작은 사이즈와 적은 파워 소모량을 우선시 하는 저가의 프로세서에서는 여전히 16비트 아키텍처가 사용되고 있다. 그러나 16비트 아키텍처는 특정 애플리케이션을 위한 특별한 명령어들을 추가할 만 한 충분한 인코딩 공간이 제공되지 않는 결정적인 단점을 가지고 있다. 이것을 극복하기 위해 기존의 많은 아키텍처에서 일반적이지 않은 다양 한 어드레싱 모드들을 수용하기 위한 직교적이지 않으면서(non-orthogonal) 불규칙한 명령어 셋이 사용되었다. 일반적으로 직교적이지 않은 아 키텍처들은 최적의 코드를 생성하기 위해서 매우 정교한 컴파일러 기술을 요구하는 경향이 있기 때문에 컴파일러에 지향적이지 않는 것으로 간주된다. 이전에 우리는 이런 문제를 해결하기 위해 새로운 어드레싱 모드인 DIAM (dynamic implied addressing mode)을 사용하는 컴파일러 지향적 프로세서를 제안하였다. 이 논문에서는16비트 프로세서에서 우리의 애플리케이션들을 위해 더 많은 인코딩 공간을 제공하였던 DIAM을 사용하는 아키텍처를 설명하고, 그것을 보완하여 성능이 더욱 개선된 아키텍처에 대하여 설명할 것이다. 우리의 실험에서 제안된 아키텍처는 기존의 아키텍처에 비해 평균적인 성능을 11.6% 증가시켰다.

• 한국지진공학회논문집
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• 제23권4호
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• pp.201-209
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• 2019

Response modification factors of school facilities for non-seismic RC moment frames with partial masonry infills in 'Manual for Seismic Performance Evaluation and Retrofit of School Facilities' published in 2018 were investigated in the preceding study. However, since previous studies are based on 2D frame analysis and limited analysis conditions, additional verification needs to be performed to further apply various conditions including orthogonal effect of seismic load. Therefore, this study is to select appropriate response modification factors of school facilities for non-seismic RC moment frames with partial masonry infills by 3D frame analysis. The results are as follows. An appropriate response modification factor for non-seismic RC moment frames with partial masonry infills is proposed as 2.5 for all cases if the period is longer than 0.6 seconds. Also if the period is less than 0.4 seconds and the ratio of shear-controlled columns is less than 30%, 2.5 is chosen too. However, if the period is less than 0.4 seconds and the ratio of shear-controlled columns is higher than 30%, the response modification factor shall be reduced to 2.0. If the period is between 0.4 and 0.6 seconds, then linearly interpolates the response correction factor.

• 한국군사과학기술학회지
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• 제21권4호
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• pp.437-446
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• 2018

This paper describes the real-time logic implementation of orthogonal matching pursuit(OMP) algorithm for compressive sensing digital receiver. OMP contains various complex-valued linear algebra operations, such as matrix multiplication and matrix inversion, in an iterative manner. Xilinx Vivado high-level synthesis(HLS) is introduced to design the digital logic more efficiently. The real-time signal processing is realized by applying dataflow architecture allowing functions and loops to execute concurrently. Compared with the prior works, the proposed design requires 2.5 times more DSP resources, but 10 times less signal reconstruction time of $1.024{\mu}s$ with a vector of length 48 with 2 non-zero elements.

• IEIE Transactions on Smart Processing and Computing
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• 제3권4호
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• pp.181-190
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• 2014

This paper reports a cognitive radio network architecture based on overloaded multicarrier direct sequence code division multiple access (O-MC-DS-CDMA). The O-MC-DSCDMA technique combines CDMA with a multicarrier modulation technique to overcome the channel fading effects. In this technique, secondary users are enabled to share the available bandwidth with the existing primary users. Two sets of orthogonal Gold codes are used to support the primary and secondary users simultaneously. The orthogonality between the spreading codes is lost due to the non-zero cross correlation between the codes and the timing synchronization error in the uplink transmission, which causes interference between primary and secondary users. This paper proposes two modified hybrid parallel/successive interference cancellation techniques for primary and secondary user base station receivers with multiple antennas to suppress the interference among users. Interference among the same group of users is cancelled by parallel interference cancellation and the interference among groups is cancelled using successive interference cancellation. The simulation results confirmed that the proposed modified interference cancellation techniques show better BER performance over conventional interference cancellation techniques.

• 콘크리트학회논문집
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• 제16권3호
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• pp.345-356
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• 2004

다양한 압축 응력 상태에서의 콘크리트의 거동 특성을 나타내기 위한 소성 모델을 개발하였다. 응력 성분은 압축 상태에서 각각의 거동특성을 갖는 세 개의 직교 성분으로 분리하였다. 각 성분의 거동 특성을 독립적으로 나타내기 위하여 각 성분에 대한 독립적인 다중 파괴기.준을 이용하는 소성모델을 적용하였다. 각 파괴면은 실험결과에 근거하여 각 파괴기준에 대한 등가 소성 변형률에 의하여 정의하였다. 또한, 압축손상에 의한 체적팽창을 나타내기 위한 간단한 비상관 소성흐름법칙을 제안하였다. 제안된 모델은 다양한 재료 특성 및 응력 상태를 갖는 기존의 실험 결과들과 비교를 통하여 검증되었다. 이 비교는 기존의 소성모델보다 제안된 모델의 적용성이 우수함을 입증하고 있다.

• 한국산업융합학회 논문집
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• 제24권1호
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• pp.31-43
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• 2021

In this study, approximate design optimization using various meta-models was performed for the structural design of active type deck support frame. The active type deck support frame was newly developed to facilitate both transportation and installation of 20,000 ton class offshore plant topside. Structural analysis was carried out using the finite element method to evaluate the strength performance of the active type deck support frame in its initial design stage. In the structural analysis, the strength performances were evaluated for various design load conditions that were regulated in ship classification organization. The approximate optimum design problem based on meta-model was formulated such that thickness sizing variables of main structure members were determined by achieving the minimum weight of the active type deck support frame subject to the strength performance constraints. The meta-models used in the approximate design optimization were response surface method, Kriging model, and Chebyshev orthogonal polynomials. The results from approximate design optimization were compared to actual non-approximate design optimization. The Chebyshev orthogonal polynomials among the meta-models used in the approximate design optimization represented the most pertinent optimum design results for the structure design of the active type deck support frame.

• 융합정보논문지
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• 제11권1호
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• pp.109-117
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• 2021

본 논문에서는 해양자동채염기의 구조중량 최소화를 위해 구조설계에 대한 메타모델 기반 근사최적화를 수행하였다. 구조해석은 해양자동채염기의 초기설계에 대한 강도성능을 평가하기 위해 유한요소법을 이용하여 수행하였다. 구조해석에서는 설계하중조건에 대한 강도성능을 평가하였다. 최적설계문제는 강도성능 제한조건을 만족하면서 중량을 최소화할 수 있는 구조두께의 설계변수를 결정하도록 정식화하였다. 근사최적화에는 반응표면법, 크리깅 모델 및 체비쇼프 직교 다항식의 메타모델을 사용하였다. 수치계산 특성을 검토하기 위해 근사최적화 결과는 비근사최적화 결과와 비교하였다. 근사최적화에 사용된 메타모델 중 체비쇼프 직교 다항식이 해양자동채염기의 구조설계에 가장 적합한 최적설계 결과를 나타내었다.

• 산업경영시스템학회지
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• 제38권4호
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• pp.177-183
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• 2015

Incremental sheet metal forming is a manufacturing process to produce thin parts using sheet metals by a series of small incremental deformation. The process rarely needs dedicated dies and molds, thus, preparation time for the process is relatively short as to be compared to conventional metal forming. Spring back in sheet metal working is very common, which causes critical errors in dimensions. Incremental sheet metal forming is not fully investigated yet. Hence, incremental sheet metal forming frequently produces inaccurate parts. This paper proposes a method to minimize dimensional errors to improve shape accuracy of products manufactured by incremental forming. This study conducts experiments using an exclusive incremental forming machine and the material for these experiments are sheets of aluminum AL1015. This research defines a process parameter and selects a few factors for the experiments. The parameters employed in this paper are tool feed rate, tool diameter, step depth, material thickness, forming method, dies applied, and tool path method. In addition, their levels for each factor are determined. The plan of the experiments is designed using orthogonal array $L_8$ ($2^7$) which requires minimum number of experiments. Based on the measurements, dimensional errors are collected both on the tool contacted surfaces and on the non-contacted surfaces. The distances between the formed surfaces and the CAD models are scanned and recorded using a commercial software product. These collected data are statistically analyzed and ANOVAs (analysis of variances) are drawn up. From the ANOVAs, this paper concludes that the process parameters of tool diameter, forming depth, and forming method are the significant factors to reduce the errors on the tool contacted surface. On the other hand, the experimental factors of forming method and dies applied are the significant factors on the non-contacted surface. However, the negative forming method always produces better accuracy than the positive forming method.

• Journal of Communications and Networks
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• 제18권3호
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• pp.420-428
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• 2016

In this paper, we investigate the scheduling and power allocation for coordinated multi-point transmission in downlink long term evolution advanced (LTE-A) systems, where orthogonal frequency division multiple-access is used. The proposed scheme jointly optimizes user selection, power allocation, and modulation and coding scheme (MCS) selection to maximize the weighted sum throughput with fairness consideration. Considering practical constraints in LTE-A systems, the MCSs for the resource blocks assigned to the same user need to be the same. Since the optimization problem is a combinatorial and non-convex one with high complexity, a low-complexity algorithm is proposed by separating the user selection and power allocation into two subproblems. To further simplify the optimization problem for power allocation, the instantaneous signal-to-interference-plus-noise ratio (SINR) and the average SINR are adopted to allocate power in a single cell and multiple coordinated cells, respectively. Simulation results show that the proposed scheme can improve the average system throughput and the cell-edge user throughput significantly compared with the existing schemes with limited feedback.