• Wind and Structures
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• 제38권1호
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• pp.59-74
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• 2024

Large Eddy Simulation (LES) is used to explore the influence of vibration frequency and amplitude on the aerodynamic performance of a rectangular cylinder with an aspect ratio of B/D=5 (B: breadth; D: depth of cylinder) at a Reynolds number of 22,000 near resonance frequency. In smooth flow conditions, the research employs a sequence of three-dimensional simulations under forced vibration with diverse frequency ratios f_e / f_o = 0.8-1.2 (f_e : oscillation frequency; f_o : Strouhal frequency when the rectangular cylinder is stationary ) and oscillation amplitudes A_h/D = 0.05 - 0.3. The individual influences of f_e / f_o and A_h/D on the characteristics of integrated and distributed aerodynamic forces are the focal points of discussion. For the integrated aerodynamic force, particular emphasis is placed on the analysis of the dependence of velocity-proportional component C₁ and displacement-proportional component C₂ of unsteady aerodynamic force on amplitude and frequency ratio. Near the resonance frequency, the dependencies of C₁ and C₂ on amplitude are stronger than that of frequency ratio. For the distributed aerodynamic force, the increase in frequency and amplitude promotes the position of the main vortex core and reattachment to the leading edge in the streamwise direction. In the spanwise direction, vibration enhances the spanwise correlation of aerodynamic force to weaken the three-dimensional effect of the flow field, and a lower frequency ratio and larger amplitude amplify this effect.

• 디지털융복합연구
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• 제13권10호
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• pp.99-106
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• 2015

현대사회의 가장 큰 변화는 유비쿼터스 환경으로의 전환이라 하겠다. 이 환경의 변화는 결국 독자적인 경영에서 각 분야의 접목을 통한 융합경영의 시대를 열게 되는 결정적인 계기가 되었다. 소비자는 새로운 혁신제품에의 욕구가 끊임없이 나타나고 기업들은 이러한 변화에 대응하기 위한 부단한 노력을 하여야 하는 것은 결국 기업의 입장에서 융합경영은 지속경영을 위한 과제가 될 것이다. 따라서 본 연구에서는 기업의 융합경영 필요성에 근거를 두고 기업의 융합경영 구성요소가 품질혁신에 어떠한 영향을 미치는 지를 살펴보고자 한다. 연구 결과, 융합경영 구성요소인 내부요인, 외부요인, 핵심요인 모두 품질혁신에 영향을 미치는 것으로 나타났다. 세부적으로는 융합경영 내부요인은 리더십, 리스크관리요인이 긍정적으로 영향을 미치는 것으로 나타났으며, 외부요인은 지식공유요인, 인프라요인이 긍정적으로 영향을 미치는 것으로 나타났다. 마지막으로 핵심요인은 기술개발요인, 교육학습요인이 긍정적인 영향을 미치는 것으로 나타났다. 이러한 결과는 향후 융합경영을 통한 기업의 경쟁력 강화의 큰 영향요인이 될 것으로 사료되며 향후 기업의 융합경영을 위한 전략적 기초로 활용될 것이다.

• 한국자기학회지
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• 제23권2호
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• pp.49-53
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• 2013

전류센서는 하이브리드 및 전기자동차의 배터리 충 방전과 모터컨트롤러의 모니터링 시스템에 적용되는 중요한 부품이다. 본 연구에서는 자기코어의 공극에 홀센서를 위치시켜 측정전류에 의해 생성된 자기장을 감지하는 구조를 가진 open loop type의 전류센서를 개발하였다. 코어는 방향성규소강판을 사용하여 제작한 후 공극이 3 mm되게 절단하였다. 공극에서의 자기장 측정을 위하여 GaAs 홀센서를 적용하였다. 개발한 전류센서는 측정범위가 -400~+400 A에서 선형도 0.03 %를 확보하였으며, 온도보상회로를 적용하여 동작온도영역인 $-40{\sim}+105^{\circ}C$에서 전류센서의 온도특성을 향상시켰다. 전류센서의 동특성 향상을 위하여 공기자속를 제어하였다. 주파수대역폭 측정은 $40A{\cdot}turn$, 100 Hz~100 kHz의 사인파형으로 측정하여 100 kHz의 대역폭을 갖는 것으로 평가되었으며, 반응속도는 $40A{\cdot}turn$의 5 kHz 구형파로 측정하여 $2{\mu}s$ 이하의 성능을 갖는 것으로 측정되었다.

• 정보처리학회논문지D
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• 제12D권7호
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• pp.947-956
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• 2005

소프트웨어(S/W) 재공학은 S/W의 생명주기의 연장을 통한 지속적인 비즈니스 가치 창출 및 궁극적인 S/W ROI(Return on Investment) 확대에 가장 효과적인 기술 중 하나이다. 그럼에도 불구하고 S/W 재공학은 비용 소모적이며, 그 효과 역시 미흡한 어려운 작업으로 인식되어 왔다. 사실, 빈번히 발생하는 유지보수 요구에 대해 레거시 시스템들을 일치성 없이 그때그때 확장, 수정함으로써, 기존 시스템 본연의 의도를 상실 시켜 S/W시스템 아키텍쳐가 존재하지 않는 난잡한 시스템으로 전환시키는 경우가 종종 발생하고 있다. 더욱이 급격히 변하는 시스템 환경과 복잡 다양해지는 고객의 요구를 충족시킬 수 있는 새로운 S/W 시스템들을 매번 적시에(Time-to-Market) 제공하기는 거의 불가능하다. 따라서, 새로운 IT 기술의 출현과 비즈니스 정보 모델의 다양한 변경, 시스템 처리 로직의 급격한 복잡성 증가 등의 변화에 적절히 대처하기 위해서는 조직의 주요 자산으로서 레거시 시스템의 활용을 극대화할 수 있는 체계적인 재공학이 요구된다. 그러므로 본 논문에서는 레거시 시스템들의 가치를 극대화할 수 있는 체계적인 재공학 방법론 제공을 목적으로, 재공학의 초기 계획 단계에서부터 역공학 과정과 컴포넌트 변환 단계를 포함하는 재공학 프로세스와 그에 따른 구체적인 작업과 기법 및 산출물들을 명시한 레거시 시스템의 컴포넌트화 프로세스인 마르미-RE를 제안하고 간단한 사례적용 과정을 제시한다.

• Genomics & Informatics
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• 제4권1호
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• pp.11-15
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• 2006

The aim of this study is to identify hRad21-binding sites in human chromosome, the core component of cohesin complex that held sister chromatids together. After chromatin immunoprecipitation with an hRad21 antibody, it was cloned the recovered DNA and sequenced 30 independent clones. Among them, 20 clones (67%) contained repetitive elements including short interspersed transposable elements (SINE or Alu elements), long terminal repeat (LTR) and long interspersed transposable elements (LINE), fourteen of these twenty (70%) repeats clones had Alu elements, which could be categorized as the old and the young Alu Subfamily, eleven of the fourteen (73%) Alu elements belonged to the old Alu Subfamily, and only three Alu elements were categorized as young Alu subfamily. There is no CpG island within these selected clones. Association of hRad21 with Alu was confirmed by chromatin immunoprecipitation-PCR using conserved Alu primers. The primers were designed in the flanking region of Alu, and the specific Alu element was shown in the selected clone. From these experiments, it was demonstrated that hRad21 could bind to SINE, LTRs, and LINE as well as Alu.

• 한국기계가공학회지
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• 제14권2호
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• pp.1-6
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• 2015

Transmission of a tracked vehicle designed for multiple functions such as steering, gear-shifting, and braking is a core component of heavy vehicle to which the power is transferred based on combined technology of various gears, bearing, and fluid machineries. Robustness and durability of transmission, however, have been issued due to a large number of driving units and sub-components inside its body. The bevel gears are major components for the transmission of power in a transmission. Increasing the tooth surface roughness and chamfering of the bevel gears, especially, we aim to improve the quality of transmission. In this study, design structural evaluation is conducted on bevel gears of transmission for tracked vehicle using the ROMAX-DESIGNER program. By doing so, design safety of the bevel gears has been evaluated based on the gear strength theory of ANSI/AGMA 2003 B97 standard.

• 전기학회논문지
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• 제60권12호
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• pp.2246-2253
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• 2011

This paper presents the error correction method of magnetic position sensor using recursive least square method (RLSM) with forgetting factor. Magnetic position sensor is proposed for linear position detection of the linear motor which has tooth shape stator, consists of permanent magnet, iron core and linear hall sensor, and generates sine and cosine waveforms according to the movement of the mover of the linear motor. From the output of magnetic position sensor, the position of the linear motor can be detected using arc-tan function. But the variation of the air gap between magnetic position sensor and the stator and the error in manufacturing process can cause the variation in offset, phase and amplitude of the generated waveforms when the linear motor moves. These variations in sine and cosine waveforms are changed according to the current linear motor position, and it is very difficult to compensate the errors using constant value. In this paper, the generated sine and cosine waveforms from the magnetic position sensor are compensated on-line using the RLSM with forgetting factor. And the speed observer is introduced to reduce the effect of uncompensated harmonic component. The approaches are verified by some simulations and experiments.

• 한국전자거래학회지
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• 제6권3호
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• pp.63-80
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• 2001

The construction of the students knowledge in e-Learning systems, namely the student modeling, is a core component used to develop e-Learning systems. However, existing e-Learning systems have many problems to share the knowledge in a heterogeneous student model and a distributed knowledge base. Because the methods of the knowledge representation are different in each e-Learning systems, the accumulated knowledge cannot be used or shared without a great deal of difficulty. In order to share this knowledge, existing systems must reconstruct the knowledge bases. Consequently, we propose a new a Case Markup Language based on XML in order to overcome these problems. A distributed e-Learning systems fan have the advantage of easily sharing and managing the heterogeneous knowledge base proposed by CaseML. Moreover students can generate and share a case knowledge to use the communication protocol of agents. In this paper, we have designed and developed a CaseML by using a knowledge markup language. Furthermore, in order to construct an intelligent e-Learning systems, we have done our research based on the design and development of the intelligent agent system by using CaseML.

• 한국멀티미디어학회논문지
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• 제20권8호
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• pp.1369-1378
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• 2017

Pub/Sub (Publish/Subscribe) paradigm is a simple and easy to use model for interconnecting applications in a distributed environment. In general, subscribers register their interests in a topic or a pattern of events and then asynchronously receive events matching their interest, regardless of the events' publisher. In order to build a low latency lightweight pub/sub system for Internet of Things (IoT) services, we propose a GQSFPS (Group Quorum System-based Fog Pub/Sub) system that is a core component in the event-driven service oriented architecture framework for IoT services. The GQSFPS organizes multiple installed pub/sub brokers in the fog servers into a group quorum based P2P (peer-to-peer) topology for the efficient searching and the low latency accessing of events. Therefore, the events of IoT are cached on the basis of group quorum, and the delay-sensitive IoT applications of edge devices can effectively access the cached events from group quorum fog servers in low latency. The performance of the proposed GQSFPS is evaluated through an analytical model, and is compared to the GQPS (grid quorum-based pud/sub system).

• Computers and Concrete
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• 제21권3호
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• pp.299-310
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• 2018

When reinforced concrete structures are subjected to strong seismic forces, their beam-column connections are very susceptible to be damaged during the earthquake event. Consequently, structural designers try to fit an important quantity of steel reinforcement inside the connection, complicating its construction without a clear justification for this. The aim of this work is to evaluate -and demonstrate- numerically how the quantity and the array of the internal steel reinforcement influences on the nonlinear response of the RC beam-column connection. For this, two specimens (extracted from an experimental test of 12 RC beam-column connections reported in literature) were modeled in the Finite Element code FEAP considering different stirrup's arrays. The nonlinear response of the RC beam-column connection is evaluated taking into account the nonlinear thermodynamic behavior of each component: a damage model is used for concrete; a classical plasticity model is adopted for steel reinforcement; the steel-concrete bonding is considered perfect without degradation. At the end, the experimental responses obtained in the tests are compared to the numerical results, as well as the distribution of shear stresses and damage inside the concrete core of the beam-column connection, which are analyzed for a low and high state of confinement.