• 인터넷정보학회논문지
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• 제12권1호
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• pp.119-130
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• 2011

UML 다이어그램은 시스템을 모델링 하기 위한 언어로 사실상 표준으로 널리 사용되고 있다. 그 가운데 특히 클래스다이어그램은 시스템을 클래스와 클래스들간 관계로 시각화한 것으로 순공학적, 역공학적 시스템 모델링 및 구현에 직접적인 영향을 미친다. 많은 연구에서 클래스다이어그램의 레이아웃과 복잡성이 시스템 모델링의 이해에 미치는 영향을 설명하고 있다. 하지만 연구 결과가 혼재되어 있어 레이아웃 적용의 효과를 판단하는데 어려움이 따른다. 따라서 본 연구에서는 기존 연구에서 제시된 클래스다이어그램 레이아웃 기준을 토대로 2 (레이아웃) ${\times}$ 2 (복잡성) 실험을 설계, 레이아웃 적용으로 인한 이해도를 측정하였다. 47명의 피험자가 실험에 참여하여 서로 다르게 제시된 레이아웃과 복잡성에 대해 이해하도록 하였다. 그 결과 레이아웃을 적용한 실험 그룹에서 유효한 효과를 나타내었고 뿐만 아니라 복잡성에서도 유효한 결과를 확인할 수 있었다. 하지만 이 둘의 상호작용 측정에 있어서는 유효한 결과를 얻지 못했다.

• ETRI Journal
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• 제30권6호
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• pp.807-817
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• 2008

We present a low-density parity-check (LDPC)-based, threaded layered space-time-frequency system with emphasis on the iterative receiver design. First, the unbiased minimum mean-squared-error iterative-tree-search (U-MMSE-ITS) detector, which is known to be one of the most efficient multi-input multi-output (MIMO) detectors available, is improved by augmentation of the partial-length paths and by the addition of one-bit complement sequences. Compared with the U-MMSE-ITS detector, the improved detector provides better detection performance with lower complexity. Furthermore, the improved detector is robust to arbitrary MIMO channels and to any antenna configurations. Second, based on the structure of the iterative receiver, we present a low-complexity belief-propagation (BP) decoding algorithm for LDPC-codes. This BP decoder not only has low computing complexity but also converges very fast (5 iterations is sufficient). With the efficient receiver employing the improved detector and the low-complexity BP decoder, the proposed system is a promising solution to high-data-rate transmission over selective-fading channels.

• 융합정보논문지
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• 제8권5호
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• pp.101-106
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• 2018

자산을 등록 관리하기 위한 다양한 소프트웨어가 연구되고 있으며 이와 같은 소프트웨어 시스템을 평가하기 위한 방법은 주관적인 평가기준을 대상으로 이루어져왔다. 본 연구에서는 선행된 자산관리 시스템의 복잡도 측정으로부터 얻어진 복합자산을 평가하기 위한 평가모델을 제안하고자 한다. 아키텍처 자산의 복잡성을 측정하기 위해 논리적 복잡도를 측정하여 제공하는 척도를 이용하였으며, 아키텍처 자산의 속성 값을 표현하고 있는지를 평가하기 위한 방법을 사용 하였다. 소프트웨어 평가 표준인 SQuaRE Series의 ISO/IEC 25010 품질 모델 특성을 기반으로 자산데이터의 사용성을 평가하기 위한 부특성의 평가모델 기준을 구축하였다. 자산은 복합자산으로 구성되어 설계되었을 때 각 자산의 특성에 따라 가중치를 부여한 부특성의 선택적 평가를 적용하여 평가모델의 유연성을 확보하도록 하였다.

• ETRI Journal
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• 제39권3호
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• pp.326-335
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• 2017

In the uplink transmission of massive (or large-scale) multi-input multi-output (MIMO) systems, large dimensional signal detection and its hardware design are challenging issues owing to the high computational complexity. In this paper, we propose low-complexity hardware architectures of Richardson iterative method-based massive MIMO detectors. We present two types of massive MIMO detectors, directly mapped (type1) and reformulated (type2) Richardson iterative methods. In the proposed Richardson method (type2), the matrix-by-matrix multiplications are reformulated to matrix-vector multiplications, thus reducing the computational complexity from $O(U^2)$ to O(U). Both massive MIMO detectors are implemented using a 65 nm CMOS process and compared in terms of detection performance under different channel conditions (high-mobility and flat fading channels). The hardware implementation results confirm that the proposed type1 Richardson method-based detector demonstrates up to 50% power savings over the proposed type2 detector under a flat fading channel. The type2 detector indicates a 37% power savings compared to the type1 under a high-mobility channel.

• 대한조선학회논문집
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• 제53권4호
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• pp.258-265
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• 2016

A flexible riser consists of several layers which have different materials, shapes and functions. The layers designed properly can take the design load safely, and each property of layer provides a complexity of flexible riser. Such complexity/unit-property is an input for global analysis of flexible riser. There are several approaches to calculate the complexity of flexible riser, those are experimental, numerical and theoretical methods. This paper provides a complexity from numerical and theoretical analysis for 2.5 inch flexible riser of which details and the experimental data are already produced under tension, external pressure, and bending moment. In addition, comparison of stiffness and stress are also provided. Especially, analysis of stress could lead to researches on ultimate strength or fatigue strength of flexible risers.

• 유통과학연구
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• 제17권12호
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• pp.13-21
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• 2019

Purpose - It is very important to examine customer's behavior about AR shopping either practically or academically. Thus, it will be worthwhile to discuss more in details about AR utility which is even in early stage of distribution industry now. Research design, data, and methodology - This study has designed in consideration of control effects of perceived complexity based on customer's flow as dependent variable, and on AR characteristics and technology readiness as independent variables. Study data has been collected from questionnaires after using AR shopping service directly by those who are 20-30 years old of male and female respondents, which has been analyzed with 167 questionnaires. Hypothesis is verified using by hierarchical regression analysis. Results - After results of hypothesis verified, positive influence has been shown in terms of sensory immersion, manipulation, and optimism, however, it is rejected in relation to navigation and innovativeness. Control effect of perceived complexity has not been appeared. Conclusions - Implications of this study are as follows. First, AR shopping service has to provide an informational value. Second, by providing AR service to customer group, marketing activities will be in effects. Third, recognized complexity is not connected with significant control effect in terms of customer's devotion of service.

• 복식문화연구
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• 제8권1호
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• pp.30-39
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• 2000

The purpose of this study were to 1) identify types and levels of production environments, 2) classify apparel manufacturers based on production environments and 3) investigate relationship between characteristics of apparel manufacturers and production environment. Apparel manufacturer's characteristics included product line and the number of employees. For this study, the questionnaires were administered to 215 apparel manufacturers in seoul and Kyung-gi region from Feb. to Mar. 1998. Employing a sample of 201, data were analyzed by factor analysis, descriptive statistics, cluster analysis, cluster analysis, discriminant Analysis, and multivariate analysis of variance. The following are the results of this study : 1. The production environment was identified as three types such as complexity of product environment, uncertainty of demand/supply environment and uncertainty of worker environment. 2. Based on three types of the production environment, apparel manufacturers were classified into stable group, uncertain group and complicated group. 3. With respect to product line, men's wear manufacturers were lied the most high complexity of product environment, casual wear and knit wear were lied the most frequently uncertainty of worker environment. With respect to the number employees, apparel manufacturers comprising 50∼99 employees were lied the most high complexity of product environment, while those comprising 100∼299 employees the most high demand/supply environment.

• 디지털산업정보학회논문지
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• 제10권1호
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• pp.113-120
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• 2014

In this paper, I present a new echo canceller using the adaptive cascade system identification (CSI) method, which a system response is divided into several responses so that each response is adaptively estimated and combined. Echo cancellation is required for a dual-duplex DSL, in order to allow each individual loop to operate in a full duplex fashion. Echo cancellation was one of the most difficult aspects of DSL design, requiring high linearity and total echo return loss in excess of 70 dB. Especially, for a fickle response, if the response is estimated by an adaptive filter, the filter needs more taps and the performance is decreased. But the response is divided into several responses, the computation complexities are decreased and the performance is increased. For the stage constant n, which represents the number of stages, if the response is not divided (n=1), the computation complexity of multiply is $2N^2$. And if the response is divided into two responses (n=2), the computation complexity of multiply is $2N^2$. Also, if n=3, the computation complexity is ${\frac{2}{3}}N^2$. Therefore, it is known that the computation complexity is decreased as n is increased. Finally, this proposed method is verified through simulation of echo canceller for digital subscriber line (DSL) application.

• 한국통신학회논문지
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• 제22권9호
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• pp.2053-2061
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• 1997

움직임 보상 부호화 가법은 연속한 비디오 프레임간의 시간적 증복성을 제거하기 때문에 비디오 영상 압축에 매우 중요한 역합을 한다. 그러나 많은 계산량으로 인하여 실시간 응용이나 고해상도 응용에 많은 어려움이 있다. 이러한 문제점을 해결하기 위하여 빠른 탑색 가법과 하드웨어 설계 기법이 활발히 연구되어 왔다. 특히 계산량을 크게 줄이고 안정된 성능을 갖는 삼단계 탐색 기법이 널리 이용되고 있으며 이를 기반으로 한 새로운 탐색 기법들이 제안되었다 본 논문에서는 인접한 블럭들의 움직임 벡터가 미치는 영향을 고려하여 수정된 삼단계 탐색 기법을 제안하고 이의 성능을 평가한다. 실험에 의하여 제안된 기법이 삼단계 탐색 기법에 비교하여 적은 계산량을 가지며, MAE 측면에서 이득이 있음을 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권6호
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• pp.2908-2924
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• 2019

Multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) is widely applied in wireless communication by virtue of its excellent properties in data transmission rate and transmission accuracy. However, as a major drawback of MIMO-OFDM systems, the high peak-to-average power ratio (PAPR) complicates the design of the power amplifier at the receiver end. Some available PAPR reduction methods such as selective mapping (SLM) suffer from high computational complexity. In this paper, a low-complexity SLM method based on active constellation extension (ACE) and joint space-time selective mapping (AST-SLM) for reducing PAPR in Alamouti STBC MIMO-OFDM systems is proposed. In SLM scheme, two IFFT operations are required for obtaining each transmission sequence pair, and the selected phase vector is transmitted as side information(SI). However, in the proposed AST-SLM method, only a few IFFT operations are required for generating all the transmission sequence pairs. The complexity of AST-SLM is at least 86% less than SLM. In addition, the SI needed in AST-SLM is at least 92.1% less than SLM by using the presented blind detection scheme to estimate SI. We show, analytically and with simulations, that AST-SLM can achieve significant performance of PAPR reduction and close performance of bit error rate (BER) compared to SLM scheme.