• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1191-1195
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• 2007

Many approximate models for interaction between a flexible structure and an infinite external acoustic medium have been developed for a long time. Among them, Doubly Asymptotic Approximations (DAAs) are very well known approximations. But, it has shortcomings in intermediate frequency range and can't fully describe the acoustic medium. So, this paper presents the modified approximation by applying the retarded and advanced potentials to Kirchhoff's formula. It describes the external acoustic medium more in detail and shows a good result in early time transient responses when it was applied to a spherical shell. Through a spherical shell interacting with external acoustic medium, the transient responses for the proposed model is compared to Huang's exact solution and DAA2.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05b
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• pp.1489-1492
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• 2003

이동 컴퓨팅 환경에서 사용자의 이동 특성은 실시간 멀티미디어 서비스를 제공하기 위해서 요구되는 QoS(Quality of Service)에 심각한 영향을 미친다. RSVP(Resource reservation Protocol)는 유선을 기반으로 실시간 서비스를 제공하기 위해서 제안된 프로토콜로써 이동 환경에 적용하기에는 부적합하다. MRSVP(Mobile RSVP)는 RSVP를 기반으로 사용자의 이동이 QoS에 미치는 영향을 최소화하기 위해서 사용자가 이동할 것으로 예상되는 영역에 대한 자원을 미리 예약하는 프로토콜이다. 본 논문은 기존의 MRSVP를 확장하여 Mobile IP 지역등록(Regional Registration) 프로토콜과 이웃 라우터 발견 메커니즘(Neignbor Router Discovery Mechanism)을 결합하여 동적 앵커 에이전트(DAA: Dynamic Anchor Agent)를 계층적으로 구성하는 QoS지원 방안을 제안한다. 이는 기존의 MRSVP에서 미리 예약되는 자원예약 범위를 네트워치 위상을 고려하여 지역적으로 제한함으로써 자원예약을 최소화하는 반면에 기존의 MRSVP와 유사한 수준의 QoS 보장을 목적으로 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.18-21
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• 2016

VDI 기반 가상 세스크탑 사용자에게 높은 만족도를 제공하기 위해서는 높은 CPU 속도 및 충분한 메모리와 저장공간, 네트워크 대역폭 등의 고성는 디바이스를 제공할 필요가 있다. 하지만 VDI 구축은 많은 비용이 소모되므로 서비스 사용자 수를 고려하여 해당 인프라 규모를 신중하게 결정할 필요가 있다. 특히 클라우드 기반 VDI 서비스에서는 각 서버에서 구동하는 가상 데스크탑의 수가 증가함에 따라 하이퍼바이저의 관리에 대한 연산이 증가하여 서버의 가용성이 감소된다. 본 논문에서는 한국전자통신연구원에서 개발한 클라우드 DaaS 시스템을 기반으로 VDI 산업 표준 성능 테스트 도구인 LoginVSI를 사용하여, 서비스 규모별 최적의 VDI 솔루션을 찾아내고 구축하기 위한 성능 측청 방법을 제시하고 결과를 분석 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.979-984
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• 2003

A Dynamic vibration absorber(DVA) is developed to reduce the excessive vibration of an optical disk drive(ODD) originated from the deriving range of an wobble disk and unbalanced disk. We design the material properties and shapes of the DVA by simulating Frequency response function(FRF) such as target frequency, mass of the DVA, stiffness of damper, damping coefficient, shape and dimension, analyze dynamic characteristics and provide its design guide line for suppressing the vibration of an optical disk derive. To examine the performance of the DVA, the vibration of the feeding system with DVA and without DAA are measured by using a three-axis accelerometer, PCB derive and Pulse analyzer. The result show that the proposed DVA reduces the vibration of wide range in ODD.

• TTA Journal
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• s.139
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• pp.40-43
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• 2012

주로 컴퓨터 자원(Platform, HDD, CPU)의 가상화를 통한 IT 인프라 관리 및 아웃소싱의 효율성을 추구하던 클라우드 컴퓨팅이 이제는 다양한 서비스 분야로 전환되고 있다. 심지어 사용자의 개인 데이터, 홈 가전기기, 헬스 기기 등의 모든 디지털화된 IT 자원이 스마트 폰, 태블릿 PC, IP-TV 중심의 N-Screen 등의 사용자 단말 기술들과 연계 및 진화하여 더욱 편리한 디지털 라이프의 변화를 주도하고 있다. 따라서 본 특집에서는 더욱 발전하는 클라우드 컴퓨팅의 주요 분야들 - 모바일 클라우드, DaaS(Desktop as a Service: 데스크톱 클라우드), 공공 부문의 SLA(Service Level Agreement), 퍼스널 클라우드 보안과 프라이버시 - 대해 기술적 동향과 이슈 등을 고찰하고자 한다. 특히 작금의 국제적 표준화가 ITU-T, ISO에서 조직과 체계를 구체적으로 마련하고 2012년부터는 본격적인 경쟁에 들어가는 중요한 시대적 위치에 있으므로 본 특집을 통해 국내 연구자 및 개발자들에게 표준화된 기술 및 서비스 개발에 동기를 부여하고자 한다. 본 특집을 기획하면서 클라우드 컴퓨팅은 IT의 인프라에서 응용까지 연계되어 서비스 산업의 좋은 모델로서 국가적 경쟁력을 끌어올릴 수 있는 중요한 기술임이 자명하며, 단기적으로 끝나는 기술이 아님을 다시 한 번 확인할 수 있는 좋은 기회로 산업의 많은 분야에 뿌리 깊이 내려지길 기대해 본다. 이를 위해 기업과 국가의 지속적인 개발과 지원에 대한 결정이 그 어느 때보다 필요하다.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.118-131
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• 1995

The shock fracture analysis for the structures of navy vessels subject to underwater explosions or of high speed vessels frequently subject to impact loads has been carried out in two steps such as the global or macro analysis and the fine or micro analysis. In the macro analysis, Doubly Asymptotic Approximation(DAA) has been applied. The three main failure modes of structure members subject to strong shock loading are late time fracture mode such as plastic large deformation mainly due to dynamic plastic buckling, and the early time fracture mode such as tensile tearing failure or transverse shear failure. In this paper, the tensile tearing failure mode is numerically analyzed for the micro analysis by calculating the dynamic stress intensity factor $K_I(t)$, which shows the relation between stress wave and crack propagation on the longitudinal stiffener of the model. Especially, in calculating this factor, the numerical caustic method developed from shadow optical method of caustic well known as experimental method is used. The fully submerged vessel is adopted for the macro analysis at first, of which the longitudinal stiffener, subject to early shock pressure time history calculated in macro analysis, is adopted for the micro analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.9
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• pp.806-813
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• 2012

In a cloud computing environment, various solutions were introduced to provide the service to users such as Infrastructure as a Service (IaaS), Platform as a Service (PaaS), Software as a Service (SaaS) and Desktop as a Service (DaaS). Nowadays, Mobile as a Service (MaaS) to provide the mobility in a cloud environment. In other words, users must have access to data and applications even when they are moving. Thus, to support the mobility to a mobile Thin-Client is the key factor. Related works to support the mobility for mobile devices were Mobile IPv6 and Proxy Mobile IPv6 which showed performance drawbacks such as packet loss during hand-over which could be very critical when collaborating with cloud computing environment. The proposed model in this paper deploys middleware and replica servers to support the data transmission among cloud and PMIPv6 domain. It supports efficient mobility during high-speed movement as well as high-density of mobile nodes in local mobility anchor. In this paper, through performance evaluation, the proposed scheme shows the cost comparison between previous PMIPv6 and verifies its significant efficiency.

• Korean Journal of Weed Science
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• v.14 no.3
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• pp.171-175
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• 1994

Physiological changes in Eleocharis kuroguwai Ohwi as affected by bensulfuron-methyl {Methyl 2-[[[[[(4, 6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino] sulfonyl]methyl]benzoate} was determined to relate the characteristics with regrowth behavior. There were no changes in relative growth rate(RGR) during the period of growth cessation after application of bensulfuron-methyl. RGR's of the growth ceseased plants caused at 39 and 51 g/ha began to increase in between 25 and 30 days after application (DAA) and between 30 and 35 DAA, respectively. In untreated plant tuber carbohydrate rapidly decreased right after emergence and almost consumed within 40 days. There was no carbohydrate consumption during the period of growth cessation in bensulfuron-methyl-applied plant, but the content started to rapidly decrease with regrowth. Tuber viability lasted for 30 days in untreated plant, while tubers were viable for 60 and 70 days after application of bensulfuron-methyl at 39 and 51 g/ha, respectively. During the period of growth cessation the plants kept minimum respiration and photosynthesis, but with regrowth respiration and photosynthesis were resumed and rapidly increased.

• The Korean Journal of Pesticide Science
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• v.10 no.4
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• pp.320-328
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• 2006

This study was conducted to evaluate the herbicidal efficacy of flucetosulfuron+pyrazosulfuron-ethyl against Eleocharis kuroguwai and Scirpus planiculmis and to investigate tank-mix of flucetosulfuron + pyrazosulfuron-ethyl with bentazone and 2,4-D to control sulfonylurea resistant Monochoria vaginalis and Scirpus juncoides. In controlling E. kuroguwai, flucetosulfuron + pyrazosulfuron-ethyl showed 75% control, lower than that (95%) of bentazone + MCPA, at 29 DAA (days after application), while at 60 DAA it showed 90%, greater than that of (78%) of bentazone + MCPA, with greater control than penoxsulam at all times. In case of Scirpus planiculmis control, flucetosulfuron + pyrazosulfuron-ethyl showed lower activity than bentazone + MCPA but greater than penoxsulam. Flucetosulfuron + pyrazosulfuron-ethyl showed consistently high activities against Echinochloa crus-galli and E. kuroguwai regardless of soil flooding condition, while penoxsulam and bentazone + cyhalofop showed significantly lower activity in 5 cm flooding condition than 0 cm flooding condition. Flucetosulfuron + pyrazosulfuron-ethyl did not control sulfonylurea resistant Monochoria vaginalis and Scirpus juncoides, while its tank-mix with bentazone or 2,4-D at 2/3 or 1/2-folds of their recommended rates, respectively, provided > 90% control.

• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.1-7
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• 2021

Detect and avoid (DAA) system, which is essential for the operation of UAS, detects intruding aircraft and offers the ranges of turn and climb/descent maneuver that are required to avoid the intruder. This paper uses detect and avoid alerting logic for unmanned systems (DAIDALUS) developed at NASA as a DAA algorithm. Since DAIDALUS offers ranges of avoidance maneuvers, the actual avoidance maneuver must be decided by the UAS pilot as well as the timing and method of returning to the original route. It can be readily used in real-time human-in-the-loop (HiTL) simulations where a human pilot is making the decision, but a pilot decision model is required in fast-time simulations that proceed without human pilot intervention. This paper proposes a pilot decision model that maneuvers the aircraft based on the DAIDALUS avoidance maneuver range. A series of tests were conducted using test vectors from radio technical commission for aeronautics (RTCA) minimum operational performance standards (MOPS). The alert levels differed by the types of encounters, but loss of well clear (LoWC) was avoided. This model will be useful in fast-time simulation of high-volume traffic involving UAS.