• ETRI Journal
• /
• 제32권4호
• /
• pp.622-625
• /
• 2010

In this letter, we assess the scalability of a path computation flooding (PCF) approach to compute optimal end-to-end inter-domain paths in a path computation element-based multi-domain network. PCF yields a drastically reduced network blocking probability compared to a blind per-domain path computation but introduces significant network control overhead and path computation complexity. In view of this, we introduce and compare an alternative low overhead PCF (LoPCF) solution. From the obtained results, LoPCF leads to similar blocking probabilities to PCF while exhibiting around 50% path computation complexity and network control overhead reduction.

• The Journal of the Acoustical Society of Korea
• /
• 제22권2E호
• /
• pp.69-77
• /
• 2003

Correlations between acoustic properties and bone density have been investigated in bovine cancellous bone. Speed of sound (SOS), broadband ultrasonic attenuation (BUA), and broadband ultrasonic reflection (BUR) were measured in 10 defatted bovine cancellous bone specimens in vitro. SOS showed a significant correlation with the apparent density of the bone. A comparable correlation was observed between BUA and the apparent density. BUR was rather highly correlated with the apparent density. It was shown that BUR had a weak correlation with BUA and a significant correlation with SOS. This indicates that the parameter BUR can provide important information that may not be contained in BUA and SOS and, therefore, can be useful as an alternative diagnostic parameter of osteoporosis. As expected, a linear combination of all three ultrasonic parameters in a multiple regression model resulted in a significant improvement in predicting the apparent bone density.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제4권6호
• /
• pp.1152-1168
• /
• 2010

Recently, due to the prevalence of various mobile devices and wireless broadband networks, there has been a significant increase in interest and demand for multimedia streaming services such as the mobile IPTV. In such a wireless broadband network, transmitting a continuous stream of multimedia data is difficult to achieve due to mobile stations (MSs) movement. Providing Quality of Service (QoS) for multimedia video streaming applications requires the server and/or client to be network-aware and adaptive. Therefore, in order to deploy a mobile IPTV service in wireless broadband networks, offering users efficient wireless resource utilization and seamlessly offering user perceived QoS are important issues. In this paper, we propose a new adaptive streaming scheme, called MARC (Mobile-aware Adaptive Rate Control), which adjusts the quality of bit-stream and transmission rate of video streaming based on the wireless channel status and network status. The proposed scheme can control the rate of multimedia streaming to be suitable for the wireless channel status by using awareness information of the wireless channel quality and the mobile station location. The proposed scheme can provide a seamless multimedia playback service in wireless broadband networks in addition to improving the QoS of multimedia streaming services. The proposed MARC scheme alleviates the discontinuity of multimedia playback and allocates a suitable client buffer to the wireless broadband network. The simulation results demonstrate the effectiveness of our proposed scheme.

• 세라미스트
• /
• 제22권1호
• /
• pp.56-69
• /
• 2019

Recent advances in low-power sensors and transmitters are driving the search for standalone power sources that utilize unused ambient energy. These energy harvesters can alleviate the issues related to the installation and maintenance of sensors. Particularly piezoelectric energy harvesters, with the ability to convert ambient mechanical energy into useful electricity, have received significant attention due to their high energy density, low cost and operational stability over wide temperature and pressure conditions. In order to maximize the generated electrical power, the natural frequency of the piezoelectric energy harvester should be matched with the dominant frequency of ambient vibrations. However, piezoelectric energy harvesters typically exhibit a narrow bandwidth, thus, it becomes difficult to operate near resonance under broadband ambient vibration conditions. Therefore, the resonating of energy harvesters is critical to generate maximum output power under ambient vibration conditions. For this, energy harvesters should have broadband natural frequency or actively tunable natural frequency with ambient vibrations. Here, we review the most plausible broadband energy harvesting techniques of the multi-resonance, nonlinearity, and self-resonance tuning. The operation mechanisms and recent representative studies of each technique are introduced and the advantages and disadvantages of each method are discussed. In addition, we look into the future research direction for the broadband energy harvester.

• 한국인터넷방송통신학회논문지
• /
• 제10권3호
• /
• pp.83-89
• /
• 2010

본 논문은 간섭원으로써 4.5 GHz를 사용하는 UWB 센서가 동대역을 사용하는 피간섭원 광대역 무선 시스템에 미치는 간섭을 분석하였다. 분석방법으로는 Minimum Coupling Loss(MCL)와 Spectrum Engineering Analysis Monte Carlo Advanced Tool(SEAMCAT)을 사용하였으며 그 결과는 다음과 같다. 양립성 확보를 위해서 UWB 센서와 광대역 무선 시스템의 이동국 사이에는 1.2 m 이상의 보호 이격거리가 요구되었고 다수의 UWB 센서가 존재하는 경우에는 간섭 확률 5 % 이하를 만족하기 위해 UWB 수신기 PSD는 -68.5 dBm/MHz 이하로 요구되었다.

• 한국위성정보통신학회논문지
• /
• 제9권4호
• /
• pp.87-90
• /
• 2014

환경시설물의 광대역 통합모뎀 근거리 통신망 스위칭 기술을 통하여 상시 실시간 자료 수집 및 이력관리가 가능함에 따라 안정적이고 효율적인 시설물 관리 및 광대역 통합모뎀을 기반으로 적용 가능한 신기술 융합의 환경 시설물의 실용화가 필요한 상황이다. 따라서 본 논문에서는 환경시설물에 적용 가능한 광대역 통합모뎀 근거리 통신망 스위칭 기술을 제시하였다. 광대역 통합모뎀의 구축방안 및 통신방식을 제시하여 광대역 통합망 유비쿼터스 기반의 환경시설물 관리용 신기술 동향 및 기술을 분석하고, IEEE802.11x와 IEEE802.15.4x 두 가지 통신방식의 연동을 통하여 환경시설물 내 시설물로부터 수신되어지는 데이터의 수집, 해석 및 처리를 통해 이상현상 발생 시 우선순위 부여 등의 워크플로우 기능과 다수의 측정 데이터를 사용자 정의 로직에 따라 서버로 전송하는 기능을 모의실험하고 분석하여 그 유용성을 입증하였다.

• 한국초전도학회:학술대회논문집
• /
• 한국초전도학회 2001년도 High Temperature Superconductivity Vol.XI
• /
• pp.38-38
• /
• 2001

• ETRI Journal
• /
• 제26권6호
• /
• pp.589-596
• /
• 2004

Packaging technologies for a broadband and narrowband modulator with a traveling wave electro-absorption modulator (TWEAM) device were developed. In developing a broadband modulator, the effects of the device and packaging designs on the broadband performance were investigated. The optimized designs were obtained through a simulation with the result that we developed a broadband modulator with a 3 dB bandwidth of 38 GHz in the electrical-to-optical (E/O) response, an electrical return loss of less than -10 dB at up to 26 GHz, an rms jitter of 1.832 ps, and an extinction ratio of 5.38 dB in a 40 Gbps non-return to zero (NRZ) eye diagram. For analog application, the effect of the RF termination scheme on the fractional bandwidth was studied. The microstrip line with a double stub as a matching circuit and a laser trimming process were used to obtain an $S_{11}$ of -34.58 dB at 40 GHz and 2.9 GHz bandwidth of less than -15 dB.

• 한국소음진동공학회논문집
• /
• 제21권12호
• /
• pp.1138-1145
• /
• 2011

The internal broadband noise of a centrifugal fan in a household refrigerator is predicted using hybrid CAA techniques based on stochastic turbulent synthetic model. First, the unsteady flow field around the centrifugal fan is predicted using computational fluid dynamics(CFD) method. Then, the turbulent flow field is synthesized by applying the stochastic turbulent synthetic technique to the predicted flow field. The aerodynamic noise sources of the centrifugal fan are modeled on a basis of the synthesized turbulent field. Finally, the internal broadband noise of the centrifugal fan is predicted using the boundary element method(BEM) and the modeled sources. The predicted noise spectrum is compared with the experimental data. It is found that the predicted result closely follows the experimental data. The proposed method can be used as an effective tool for designing low-noise fans without expensive computational cost required generally for the LES and DNS simulations to resolve the turbulence flow field responsible for the broadband noise.

• 한국음향학회지
• /
• 제36권5호
• /
• pp.300-304
• /
• 2017

원통형 소나 시스템에서 기존의 광대역탐지 기법으로는 인접한 표적을 분리 탐지하는데 한계가 있다. 본 논문에서는 방위분해능을 향상을 위해 상호상관을 이용한 광대역탐지 기법을 원통형 소나 시스템에 적용한다. 제안된 기법은 상호상관을 이용한 광대역탐지 처리 이전에 분리 빔형성을 이용하여 동일 지향방위의 좌.우 반 빔을 생성한다. 생성된 좌 우 반 빔간의 상관관계 결과를 방위 값으로 변환하여 표적의 방위를 추정한다. 시뮬레이션을 통하여 제안된 기법이 기존의 광대역탐지 기법보다 성능이 우수함을 검증하였다.