• Journal of the Korean Data and Information Science Society
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• 제19권1호
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• pp.25-36
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• 2008

Error Correcting Output Codes (ECOC) can improve generalization performance when applied to multicategory classification problem. In this study we propose a new criterion to select hyperparameters included in ECOC scheme. Instead of margins of a data we propose to use the probability of misclassification error since it makes the criterion simple. Using this we obtain an upper bound of leave-one-out error of OVA(one vs all) method. Our experiments from real and synthetic data indicate that the bound leads to good estimates of parameters.

• 대한기계학회논문집A
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• 제20권8호
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• pp.2468-2479
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• 1996

An upper bound solution is obtained to perform the process analysis of hot strip rolling process. The material flows within the roll bite at various geometries and frictional conditions are obtained from finite element analysis and the typical flow pattern which is necessary to determine the kinematically admissible velocity field is assumed. From the kinematically admissible velocity field, the upper bound energy is calculated and the rolling load, angle of neutral point and forward slip ratio at various operational conditions are obtained from upper bound energy. The process analysis of above mentioned parameters at various operational conditions have provided valuable information which is hard to obtain during rolling operation and the predicted ranges of quantitive values from these analyses lie whthin the bound of actual operational data.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권7호
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• pp.2371-2388
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• 2015

In this paper, we investigate the performance evaluation of three dimensional (3D) multiple-input multiple-output (MIMO) systems with an adjustable base station (BS) antenna tilt angle and zero-forcing (ZF) receivers in Ricean/Lognormal fading channels. In particular, we take the lognormal shadow fading, 3D antenna gain with antenna tilt angle and path-loss into account. First, we derive a closed-form lower bound on the sum rate, then we obtain the optimal BS antenna tilt angle based on the derived lower bound, and finally we present linear approximations for the sum rate in high and low-SNR regimes, respectively. Based on our analytical results, we gain valuable insights into the impact of key system parameters, such as the BS antenna tilt angle, the Ricean K-factor and the radius of cell, on the sum rate performance of 3D MIMO with ZF receivers.

• 정보과학회 논문지
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• 제44권1호
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• pp.13-20
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• 2017

메시지 처리기란 클라이언트들로부터 수신된 다양한 포맷의 메시지를 수신 메시지 별 쓰레드를 생성하여 처리하고 그 결과를 목적지로 전달하는 서버 소프트웨어를 말한다. 본 논문에서는 SEDA(The Stage Event Driven Architecture) 구조의 메시지 처리기에서 각 수행함수가 CPU 또는 IO bound 특성을 가질 수 있다는 점에 착안하여, 수행 함수 별 특성을 고려해 쓰레드를 각 코어에 매핑하는 FC-TM(Function Characteristic aware Thread Mapping) 기법을 제안하였다. 본 논문에서는 메시지 처리에 필요한 각 수행함수의 특성이 정적인 것으로 가정하였다. 따라서 수행 가능한 함수를 미리 프로파일링(profiling)하여 특성을 분석한 후, 실제 수신되는 메시지에 따라 단위시간 당 처리량(throughput)이 최대가 되도록 쓰레드를 매핑하였다. 성능 평가 결과 IO bound한 함수가 특정 비율 이상 있을 경우, 기존 연구보다 단위시간당 처리량이 최대 72%까지 증가하였다.

• 한국언어정보학회:학술대회논문집
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• 한국언어정보학회 2001년도 학술대회 논문집
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• pp.199-225
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• 2001

The main goal of this paper is to investigate and compare English, German and Korean non-head-bound-intensifiers such as English ‘x-self’, German ‘selbst’, and Korean ‘susulo, casin’. That is, this paper is mainly concerned with the semantic domain where the respective contributions of the expressions in question overlap. The phenomenon under discussion with the label “intensifiers” is regarded as universal, which provides the ground of the comparative/contrastive or semi-cross-linguistic study of this paper. Not only the semantic concept of intensification by these expressions but also the combination of grammatical features or syntactic behaviours thereof seem to have highly invariant common denominators among the wide varieties of languages, even if they come from apparently different language families. In comparing English, German and Korean intensifiers, this paper is interested in the more general features of the expressions in question rather than some language-specific idiocyncracies. Intensifiers work similarly not only in English and German, but also in Korean. Each of three languages under investigation provides some sort of a safegard against confusing instances and misleading judgements on the issues under discussion. Morphologically, however, English expressions in question agree with their rele-vant NP in number, gender and person. Whereas German and Korean counterparts do not have such specific morphological properties. Intensifiers in their non-head-bound-use are subject-oriented, just as in their head-bound use. Non-head-bound-intensifiers differ from head-bound-intensifiers mostly in their syntactic behaviours or distributional properties, whereas they share the semantic domain “intensification” regarding relevant subject-NP. They introduce an ordering and distinguish center and periphery, and ‘self-involvement (directness of involvement)’seems a additional possible characterisation of the relevant dimension of these intensifiers in common. An assertion of identity also can be reg

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권2호
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• pp.426-434
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• 2015

In this paper we proposed a dada-aided Doppler estimation method for underwater acoustic communication. The training sequence is non-dedicate, hence it can be designed for Doppler estimation as well as channel equalization. We assume the channel has been equalized and consider only flat-fading channel. First, based on the training symbols the theoretical received sequence is composed. Next the least square principle is applied to build the objective function, which minimizes the error between the composed and the actual received signal. Then an iterative approach is applied to solve the least square problem. The proposed approach involves an outer loop and inner loop, which resolve the channel gain and Doppler coefficient, respectively. The theoretical performance bound, i.e. the Cramer-Rao Lower Bound (CRLB) of estimation is also derived. Computer simulations results show that the proposed algorithm achieves the CRLB in medium to high SNR cases.

• ETRI Journal
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• 제33권5호
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• pp.689-694
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• 2011

In this paper, we study scheduling schemes for two-user two-way wireless relaying systems. Two transmission modes are considered: point-to-point direct transmission and two-way amplify-and-forward relaying. An optimal scheduling scheme that opportunistically selects the best transmission mode for each user is proposed to minimize the sum bit error rate (BER). The performance lower bound of the optimal scheduling scheme is analyzed, and closed-form expression of the lower-bound BER is derived. However, for optimal scheduling, the scheduler requires the knowledge of channel state information (CSI) of all links. To reduce the feedback information of CSI, we also propose a suboptimal scheduling scheme that selects the transmission mode using only the CSI of two direct links. Simulation results show that there are 4 dB to 8 dB gains for the proposed optimal and suboptimal schemes over the fixed direct transmission and fixed two-way relayed transmission scheme. The performance gap between the optimal and suboptimal scheduling schemes is small, which implies a good trade-off between implementation complexity and system performance.

• 한국통신학회논문지
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• 제32권5B호
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• pp.257-269
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• 2007

네트워크 계층의 MANET 라우팅 프로토콜이 개발될 때 가장 주요한 관심사는 라우팅 오버헤드 (Overhead)의 축소이다. 본 논문에서는 MANET 에서 단일 노드가 자동 네크워킹 프로토콜에 의해 IP 주소를 획득할 때의 라우팅 오버헤드 (메시지 복잡도)를 정량적으로 분석하는 수학적 방법을 제안한다. MANET에서 자동 네크워킹 프로토콜은 IP 주소 할당시 IP 주소 충돌회피에 사용된다. 메시지 복잡도는 Upper Bound에 의해 수학적으로 정량화 되고, 실제 주소 할당을 컴퓨터 시뮬레이터로 구현하여, 제안된 Upper Bound와 시뮬레이션 결과를 비교, 분석한다. 메시지 복잡도의 Upper Bound는 Worst Case 시나리오 분석에 의해 유도된다.

• 한국정보통신학회논문지
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• 제13권12호
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• pp.2525-2532
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• 2009

본 논문에서는 uncoded V-BLAST(Vertical Bell Laboratories Layered Space Time) 시스템에서 PSK 신호들을 joint-detection하기 위한 fast sphere decoder를 제안한다. 이른바 PSD라 불리는 제안된 디코더는 예비처리단계와 검색단계로 구성된다. PSD의 검색단계에서는 depth-first branch and bound 알고리즘을 통해 검출 후보가 되는 신호원들의 최상우선순위(best-first order)를 정하고 이 순위에 따라 신호를 검출하게 된다. 이 때 제안된 디코더는 최상우선순위(best-first order)를 정하는데 있어 계산복잡성을 줄이는 새로운 방법을 제안한다. 시뮬레이션 결과는 PSD에 의해 시스템의 복잡성은 줄이면서 시스템 성능은 ML과 동일하게 유지할 수 있음을 보여준다.

• 한국정보통신학회논문지
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• 제14권2호
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• pp.277-286
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• 2010

이동통신 시스템에서 발생하는 큰 문제점 중의 하나는 다중 경로에 의한 신호 진폭의 감쇄 현상인 페이딩을 들수 있다. 이 때 동기시스템에서 maximum a posteriori 신호 위상 추정값의 분산에 대한 Cramer-Rao bound를 고찰하여 수신신호의 위상을 추정한다. 나카가미 페이딩 채널에서의 위상의 분산값에 대한 Cramer-Rao 하한치를 발견하기 위해서 위상에 대한 확률 밀도 함수를 이용한다. 또한 순서통계량을 이용하여 일반화된 선택 합성기법에 대한 오류 확률식을 유도하여 적절한 다이버시티 가짓수를 분석하였다.