• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
• /
• pp.183-191
• /
• 2004

The burning characteristics of interacting droplets with internal circulation in a convective flow are numerically investigated at various Reynolds numbers. The transient combustion of 2-dimensionally arranged droplets, both the fixed droplet distances of 5 radii to 40 radii horizontally and 4 radii to 24 radii vertically, is studied. The results obtained from the present numerical analysis reveal that the transient flame configuration and retardation of droplet internal motion with the horizontal or vertical droplet spacing substantially influence lifetime of interacting droplets. At a low Reynolds number, lifetime of the two droplets with decreasing horizontal droplet spacing increases monotonically, whereas their lifetime with decreasing vertical droplet spacing decreases due to flow acceleration. This flow acceleration effect is reversed when the vertical droplet spacing is smaller than 5 radii in which decreasing flame penetration depth causes the reduction of heat transfer from flame to droplets. At a high Reynolds number, however, lifetime of the first droplet is hardly affected by either the horizontal droplet spacing or flow acceleration effect. Lifetime with decreasing vertical droplet spacing increases due to reduction of flame penetration depth. Lifetime of interacting droplets exhibits a strong dependence on Reynolds number, the horizontal droplet spacing and the vertical droplet spacing and can be con-elated well with these conditions to that of single burning droplet.

• 한국군사과학기술학회지
• /
• 제13권2호
• /
• pp.336-341
• /
• 2010

The burning interruption between the initiator and the delay column in a Zr-Ni K1 delay system used for a K510 fuze occurs with long-time storage. About 10 % failure probability of 15-years stored delay systems shows the failure mode in open literature. This paper shows storage lifetime improvement results for the delay system through changing the single-base delay column into double-base ones and controlling the manufacturing processes especially the initial inclusion of humidity. The double-base delay columns was implemented by inserting one delay column of fast burning rates between the initiator and the previous delay column of slow burning rates. Accelerated aging tests of the delay systems with double-base columns, and then the firing tests were performed to evaluate the improved lifetime. The double-base delay columns shows improved storage lifetime of the delay system through preventing the failure mode.

• 대한기계학회논문집B
• /
• 제26권10호
• /
• pp.1355-1363
• /
• 2002

An experimental study was conducted to investigate the interaction phenomena of droplet array combustion in ambient environment. The droplet with 1 mm in diameter was supported from an optical fiber and ignited with a hot wire. Combustion lifetimes and burning rate constants were measured for fuel of nheptane according to parameters, which were junction and suspender spacings, and array configuration. Results show that the burning process considerably depends on the initial away configuration. The d$^2$-law is found to be correct when applied to both of the droplets in away and the single droplet. For separation distance of about 5mm, there exists a critical state. So the transition from a merged flame to separated flames occurs and burning velocity is much faster than before. Combustion lifetime of the lower droplet is shorter than that of the upper droplet in the two-dimensional arrays combustion. Burning rate constants of the droplets in arrays are smaller than that of the single droplet, while they become higher as separation distance increases. Combustion lifetimes of the droplets in arrays are longer than that of the single droplet and decrease as separation distance increase. It is concluded that the array configuration and the mergedness of the flame are the most important factors governing multi-droplet combustion.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
• /
• pp.107-113
• /
• 2007

The burning characteristics of interacting droplets with internal circulation in a convective flow are numerically investigated at various particle arrangement and size difference. In this simulation some conditions are fixed, surround gas temperature is 1250K, pressure is 10 atm and drolet's initial temperature is 300K. The transient combustion of arranged droplets, the fixed droplet distances of 4 radii to 20 radii horizontally, is studied. And the range of size of droplet is 75${\mu}m$ to 100${\mu}m$. The results obtained from the present numerical analysis reveal that the transient flame configuration and retardation of droplet internal motion with the horizontal spacing substantially influence lifetime of interacting droplets. At a Reynolds number 10, lifetime of the three droplets with decreasing horizontal droplet spacing increases monotonically. But when droplet spacing decreases further to 4radii, Lifetime of interacting droplets are increase. So Lifetime of interacting droplets exhibits a strong dependence on the horizontal droplet spacing and size difference. It can be investigated well with these conditions to that of single burning droplet.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2008년도 추계종합학술대회 B
• /
• pp.373-376
• /
• 2008

무선 센서 네트워크의 센서 노드는 다양한 최소령 센서로 구성된 저전력, 저메모리, 저컴퓨터 능력을 갖고 있다. 따라서 최근 무선 센서 네트워크의 이슈는 실용적인 응용 분야에서의 에너지 보존과 네트워크 수명을 만족하는 설계 및 개발을 요구한다. 이러한 에너지 소비량과 네트워크 수명을 만족하기 위해서 효율적인 라우팅 프로토콜 연구가 지속되어야 한다. 본 논문에서는 무선 센서 네트워크의 LEACH, LEACH-C, MTE, 그리고 PEGASIS 라우팅 프로토콜에 대해서 비교 분석하였다. 각각의 프로토콜의 운영 시간, 밧데리 소모, 총 에너지 소모량을 비교한다.

• 한국군사과학기술학회지
• /
• 제19권3호
• /
• pp.311-318
• /
• 2016

This paper shows storage life estimation of next IR(infrared) flare material through accelerated degradation tests. Three temperature conditions for the accelerated degradation tests are 55, 65 and $75^{\circ}C$. Six performances of IR flare material are burning time, IR peak/continuous Intensity, total energy of near/mid-IR and color ratio, and they were measured after the tests. Storage life of the IR flare material was estimated through both analyzing the degradation data of those performances and applying distribution-based degradation models to the data. Over 30 years of storage life at $20^{\circ}C$ is estimated in terms of IR peak intensity with reliability 0.99 and confidence level 99 %. Additionally, 10 years of storage period at $21^{\circ}C$ would be equivalent to 68 days of accelerated test at $65^{\circ}C$ from the activation energy in Arrhenius model.

• Nuclear Engineering and Technology
• /
• 제56권6호
• /
• pp.2388-2394
• /
• 2024

In our previous works, two different spherical burnable poison particles (BPPs) as B₄C and Gd₂O₃ in pin-in block type HTGR core had utilized to suppress the excess reactivity and to control long-term reactivity during the burnup period. In the present work, we performed the neutronic analysis of a prismatic HTGR operating at 850 ℃ with thermal power of 100 MW containing spherical and cylindrical BPPs and then studied the self-shielding effect of BPPs and shape effect. The calculations were performed when the surface area (1) or volume (2) of cylindrical BPPs equals to that of the spherical BPPs. The calculations showed that the neutronic parameters were slightly better for the second case than the first one, such as the excess reactivity of the reactor core at the beginning of the cycle were more suppressed, the core lifetime were more extended, and the fuel-burning were more efficiently. The neutron spectrum in each region of the cylindrical BBPs slightly differs than that of the spherical BPPs. Therefore, the self-shielding effect of BPPs on reactor core performance depends on the particle's geometrical shape.

• 한국정보과학회논문지:정보통신
• /
• 제32권2호
• /
• pp.203-214
• /
• 2005

3G 네트워크와 무선랜의 통합은 서로 간의 보완적 특성으로 인하여 학계나 산업계에서 큰 관심사가 되고 있다. 이 주제는 최근 떠오르는 이슈로서 끊김 없는 계층적 핸드오프 지원은 네트워크 통합에 따른 중요한 관심사 중 하나로 인식되고 있다. 본 논문에서는 강결합 시스템에서의 계층적 핸드오프에서 단말의 에너지 소모를 고려하는 네트워크 인터페이스 선택 알고리즘을 제안한다. 본 저자들이 제안하는 Wise Interface SElection (WISE) 알고리즘은 네트워크와 이동 단말의 협력 하에 네트워크 인터페이스카드의 에너지 특성과 현재 서비스 받고 있는 네트워크 상태, 그리고 송수신하는 데이타 양을 종합적으로 고려하여 이동 단말이 효율적으로 에너지를 소비할 수 있는 적절한 네트워크로 서비스 받을 수 있도록 유도한다. 제안된 계층적 핸드오프 알고리즘은 에너지 소비 패턴을 고려하여 다운링크와 업링크에 대하여 독립적으로 동작한다. 3G 네트워크 인터페이스 만을 사용하는 경우와 무선랜 인터페이스 만을 사용하는 경우에 비해 제안된 WISE 알고리즘이 확연히 더 적은 에너지를 소비하여 이동 단말의 동작 시간을 연장시킬 수 있다는 것을 모의 실험을 통해 증명한다. 또한 TCP 트래픽의 경우 WISE 알고리즘의 비대칭적인 링크의 사용으로 부가적인 처리율 향상을 얻을 수 있다.