• 대한기계학회논문집A
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• 제40권9호
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• pp.783-790
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• 2016

IMU기반 자세결정에 있어 추정 정확도의 저하요인 중 주요한 한 가지는 운동체의 가속도이다. 이는 가속도가 크게 발생하는 경우 가속도계 신호는 더이상 수직축 참조벡터가 될 수 없기 때문이다. 이에 대한 대책으로 일부 자세추정 알고리즘에서는 가속도 보상 메카니즘이 적용되어 왔다. 가장 보편적이고 간단한 스위칭 방법부터 적응추정방식, 가속도 모델기반 방식 등이 제안되어 왔으나, 이들 보상 메카니즘에 대한 비교분석은 이루어 지지 않았다. 본 논문은 쿼터니언기반의 Pseudo 칼만필터를 바탕으로 하여 세 가지 가속도 보상 메커니즘의 성능을 비교분석하였다. 가속조건 실험 분석을 통해 다음을 확인할 수 있었다. (1) 가속구간에서의 추정정확도 저하를 방지하기 위해선 가속도 보상 메카니즘이 반드시 필요하다. (2) 단순 스위칭 방법도 상당한 효과를 보였으나, 보다 정교한 적응추정 방식과 가속도 모델방식이 동등수준으로 가장 정확한 결과를 보였다.

• 한국콘텐츠학회논문지
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• 제20권4호
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• pp.77-85
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• 2020

이 연구는 2019년에 수행된 게임 이용자 패널 예비조사 자료를 사용하여 아동과 청소년의 사회적 관계가 게임 선용과 게임 과몰입에 미치는 영향을 분석하였다. 심리학적 접근이 중심이 된 게임이용 연구에서 게임이용자의 사회구조적 특성과 맥락을 고려한 접근은 제한적이었다. 이에 이 연구는 게임이용자의 사회적 관계와 게임이용 행태 간의 관계를 실증적으로 규명함으로써 기존 연구의 한계를 극복하고자 하였다. OLS 회귀 분석 결과 부모와 친구의 관계의 질이 게임 선용 정도와 게임 과몰입에 미치는 영향은 일관되게 나타나지 않았으며, 게임 이용자가 게임 커뮤니티 활동을 통해 얻는 게임관련 정보는 게임 선용과 게임 과몰입을 모두 강화시키는 기제로 작동하였다. 이러한 결과는 선용과 과몰입이 상호 배타적인 기제라기보다 게임이용 행태의 사회적 맥락과 관련한 해석의 틀로 작용할 가능성을 시사한다.

• IMMUNE NETWORK
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• 제9권4호
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• pp.115-121
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• 2009

Natural killer (NK) cells play key roles in innate and adaptive immune defenses. NK cell responses are mediated by two major mechanisms: the direct cytolysis of target cells, and immune regulation by production of various cytokines. Many previous reports show that the complex NK cell activation process requires de novo gene expression regulated at both transcriptional and post-transcriptional levels. Specialized un-translated regions (UTR) of mRNAs are the main mechanisms of post-transcriptional regulation. Analysis of posttranscriptional regulation is needed to clearly understand NK cell biology and, furthermore, harness the power of NK cells for therapeutic aims. This review summarizes the current understanding of mRNA metabolism during NK cell activation, focusing primarily on post-transcriptional regulation.

• BMB Reports
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• 제50권10호
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• pp.496-503
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• 2017

The human body loses several billions of cells daily. When cells die in vivo, the corpse of each dead cell is immediately cleared. Specifically, dead cells are efficiently recognized and cleared by multiple types of neighboring phagocytes. Early research on cell death focused more on molecular mechanisms of cell death regulation while the cellular corpses were merely considered cellular debris. However, it has come to light that various biological stimuli following cell death are important for immune regulation. Clearance of normal dead cells occurs silently in immune tolerance. Exogenous or mutated antigens of malignant or infected cells can initiate adaptive immunity, thereby inducing immunogenicity by adjuvant signals. Several pathogens and cancer cells have strategies to limit the adjuvant signals and escape immune surveillance. In this review, we present an overview of the mechanisms of dead cell clearance and its immune regulations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권1호
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• pp.116-130
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• 2012

Service provision and consumption platforms are more and more used to enable communication between sensors, actuators and intelligent devices, since they provide mechanisms that make possible the combination of components to create composed services. However, these kinds of platforms have limitations to adapt themselves to new and unknown devices. In this work we analyze the challenge of component or bundle communication by using the Open Services Gateway Initiative (OSGi) technology and we propose three mechanisms with the aim of contributing to flexible component communication: Common Service, Specific Service and WSIF Web Service Invocation. We provide these solutions with some architectural models and validate them through different example services. Finally we compare them regarding performance, flexibility and application complexity.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 제14회 신호처리 합동 학술대회 논문집
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• pp.907-910
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• 2001

In this paper, we address a new time delay estimation method using third-order statistics and subband adaptive filtering to improve the accuracy of target detection for acoustic backscattered signals in a noise interference environment. Each reference and primary signals are decorrelated using the multiresolution analysis framework through a M-band discrete wavelet transform(M-DWT). Then noise effect can be reduced. Here, time delays are estimated iteratively in each subband using two different adaptation mechanisms that minimize the mean squared error (MSE) between the references and primary signal. More specifically, third-order cumulants and projection cross-correlation(PCC) criterion are utilized to achieve an effective SNR improvement for the time delay estimation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.70-78
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• 1997

A DSP-based nonlinear speed control of a permanent magnet synchronous motor(PMSM) which is robust to unknown parameter variations and speed measurement error is presented. The model reference adaptive system(MRAS) based adaptation mechanisms for the estimation of slowly varying parameters are derived using the Lyapunov stability theory. For the disturbances or quickly varying parameters, a quasi-linearized and decoupled model including the influence of parameter variations and speed measurement error on the nonlinear speed control of the PMSM is derived. Based on this model, a boundary layer integral sliding mode controller to improve the robustness and performance of a PMSM drive is designed and compared with the conventional controller. To show the validity of the proposed control scheme, simulations and experimental works are carried out and compared with the conventional control scheme.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2009년도 추계학술발표논문집
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• pp.461-465
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• 2009

Normally, a distributed computing environment is flexible in controlling complex embedded systems but their software components are becoming complex as these systems are equipped with several platforms and attached to various electronic devices, sensors, and actuators. These systems requires inter-object communication mechanisms to provide fault tolerant and QoS-enabled middleware service support in a distributed system. Generally, a middleware performs analysis of the parameters to ensure the availability and reliability of data dissemination. This paper focuses in particular to designing an application middleware for the specific scenario to improve the high availability and fault tolerance of data thus improving the QoS (Quality of Service) of a distributed system. The performance of an adaptive and highly reliable middleware can be significant based on the selection of vital parameters of the system.

• 한국통신학회논문지
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• 제32권1B호
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• pp.17-21
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• 2007

본 논문에서는 멀티미디어 네트워크상에서 우선순위가 높은 서비스의 QoS를 보장하며 동시에 프로세서의 에너지 효율을 최대화하는 적응적 온라인 프로세서 관리기법을 제안하였다. 이 기법은 현재 네트워크의 트래픽 상황을 기반으로 하여 실시간으로 프로세서를 관리한다. 제안된 방법의 가장 큰 특징은 상호 상충하는 다양한 성능 메트릭들 사이에 적정한 균형을 이루어 안정적으로 시스템을 운영하는데 있다. 컴퓨터 시뮬레이션을 통하여 기존에 제안된 프로세서 관리기법에 비해 본 논문에서 제안된 방법이 다양한 트래픽 상황에서 우수한 성능을 가지는 것을 확인할 수 있었다.

• Journal of Electrical Engineering and information Science
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• 제3권2호
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• pp.251-260
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• 1998

A DSP-based robust nonlinear speed control of a permanent magnet synchronous motor(PMSM) which is robust to unknown parameter variations and speed measurement error is presented. The model reference adaptive system(MRAS) based adaptation mechanisms for the estimation of slowly varying parameters are derived using the Lyapunov stability theory. For the disturbances or quickly varying parameters. a quasi-linearized and decoupled model including the influence of parameter variations and speed measurement error on the nonlinear speed control of a PMSM is derived. Based on this model, a boundary layer integral sliding mode controller to improve the robustness and performance of the nonlinear speed control of a PMSM is designed and compared with the conventional controller. To show the validity of the proposed control scheme, simulations and experimental works are carried out and compared with the conventional control scheme.