• 대한교통학회지
• /
• 제27권3호
• /
• pp.71-77
• /
• 2009

유비쿼터스 교통환경이 구현되면 기존 ITS 환경에서는 불가능하였던, 개별차량 위치, 속도 등 미세한 데이터 수집이 가능해 지며, V2V(Vehicle-to-Vehicle), V2I(Vehicle-to-Infra) 양방통신이 가능해 짐에 따라 개별차량 혹은 차량군 단위의 미세 제어가 가능해 진다. 이러한 유비쿼터스 교통 환경의 장점에 입각하여 교통류 안정성을 지표로 하는 연속류 정체예방관리 방안이 선행연구에서 제시된 바 있다. 본 연구에서는 유비쿼터스 교통환경에서 정체예방관리를 실현함에 있어 제기된 쟁점사항들에 대하여, VISSIM 시뮬레이션 실험결과에 입각하여 해답을 제시하였다. 교통류 안정성을 명시적으로 교통류 관리에 적용할 수 있도록, 유비쿼터스 교통환경에서 수집 가능한 차량군 길이와 간격으로 도출하였다. 또한 교통상황에 따라 차별화된 운영관리가 필요하다는 타당성을 도출하고, 교통상황 구분 및 상황별 운영관리 방안을 제시하였다. 마지막으로 이러한 관리를 수행하였을 때 어떠한 잠재적 이익이 있는가를 보여주었다. 본 연구 결과는, 제반 제약조건으로 말미암아 제한적인 시뮬레이션 실험을 통해 도출되었다. 그러나 유비쿼터스 교통환경에서 새로운 개념의 교통관리를 시행하는 데 있어 그 타당성은 보여줄 수 있었다고 판단된다. 향후 보다 포괄적인 현장실험을 통해 제반 결과들이 확정되어야 할 것이다.

• Advances in nano research
• /
• 제14권2호
• /
• pp.165-177
• /
• 2023

Nanomotors are gaining popularity as novel drug delivery methods since they can move rapidly, penetrate deeply into tissues, and be regulated. The ability of manufactured nanomotors to swiftly transport therapeutic payloads to their intended location constitutes a revolutionary nanomedicine strategy. The nanomotors for the drug delivery purpose are released in the blood flow under the different physical conditions, so the stability investigation of these devices is essential before the production, especially in the sport and physical exercise conditions that the blood flow enhances. As a result, using dynamic analysis, this article investigates the stability of the nanomotor released in the blood flow when sport and physical activity circumstances increase blood flow. The considered nanodevice is made of a central motor, and nanotubes are used for the nanomotor blade, which is the drug capsule. Finally, the stability examination of nanomotor as the drug delivery equipment is discussed in detail, and the proposed results can present beneficial results in designing and producing small-scale intelligent devices.

• 대한기계학회논문집
• /
• 제15권6호
• /
• pp.1861-1871
• /
• 1991

본 연구에서는 아직까지 연구가 미진한 내용 즉, 유속과 압력이 시간과 위치 의 함수인 유동특성과 파이프의 운동이 상호 연계되어 영향을 주는 일반적인 경우의 운동방정식을 유도하였고 단순지지된 직선 파이프를 모델로 설정하여 동적 안정성 (dynamic stability)과 진동응답을 수치적으로 고찰하였다.

• 한국해양공학회지
• /
• 제35권6호
• /
• pp.403-413
• /
• 2021

As the size of ships increases, the size and output power of their thrusters also increase. When a large ship berths or unberths, the jet flow produced from its thruster has an adverse effect on the stability of quay walls. In this study, we conducted a numerical analysis to examine the impact of the thruster jet flow of a 30,000 TEU container ship, which is expected to be built in the near future, on the stability of a quay wall. In the numerical simulation, we used the fluid-structure interaction analysis technique of LS-DYNA, which is calculated by the overlapping capability using an arbitrary Lagrangian Eulerian formulation and Euler-Lagrange coupling algorithm with an explicit finite element method. As the ship approached the quay wall and the vertical position of the thruster approached the mound of the quay wall, the jet flow directly affected the foot-protection blocks and armor stones. The movement and separation of the foot-protection blocks and armor stones were confirmed in the area affected directly by the thruster jet flow of the container ship. Therefore, the thruster jet flows of ultra-large ships must be considered when planning and designing ports. In addition, the stability of existing port structures must be evaluated.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1995년도 하계학술대회 논문집 B
• /
• pp.556-558
• /
• 1995

This paper presents a new simplified method for finding the multiple load flow solutions and through their solutions the voltage stability can be evaluated. Line flow($P_{ij}$, $Q_{ij}$) may be formulated with the second-order equations for $V_{i}^{2}$ in polar coordinates or two circle equations for $e_{i}$ and $f_{i}$ in rectangular coordinates. Based on this feature, multiple load flow solutions are calculated with simple works, results of multiple load flow solutions are used for sensitivity analysis of voltage stability. Also, in the case that reactive power sources is considered, method of evaluating the voltage stability is introduced. The proposed method was validated to 2-bus and IEEE 6-bus system.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
• /
• pp.565-572
• /
• 2004

Numerical stability analysis of one-dimensional axial flow in solid rocket motors is performed based on the Euler equation coupled with an unsteady combustion equation of solid propellant. In order to check the numerical scheme, behavior of a standing wave in a closed tube is examined. A standing wave in solid rocket motor decays or grows depending on the total effect of propellant combustion, nozzle flow, and so on. The stability boundary of the fundamental mode standing wave is determined by changing one of the combustion parameters. In addition growth rates of the wave are calculated numerically in relatively low Mach number flow region for the motors with different port and nozzle throat diameters. The results obtained here agree well with the approximate solution. The same scheme is applied to a motor with shorter length and L＊-instability is observed.

• 대한전기학회논문지:전력기술부문A
• /
• 제50권2호
• /
• pp.83-89
• /
• 2001

This paper introduces a power flow model of SSSC for voltage stability analysis of power system installed with Static Synchronous Compensators. The SSSC model is obtained from the injection model of voltage source inverter by adding the condition that SSSC injection voltage is in quadrature with current of SSSC-installed branch. This model is incorporated into modified CPF algorithm to study effects of SSSC on the security-constrained interface flow limit. Determination of interface flow limit is simply briefed. In case study a 771-bus real system is used to show that interface flow limit can be improved by appropriate control of SSSC in terms of voltage stability.

• Journal of Electrical Engineering and Technology
• /
• 제8권4호
• /
• pp.694-703
• /
• 2013

In electric power system, the line stability indices adopted in most of the instances laid stress on variation of reactive power than real power variation of the transmission line. In this paper, a proposal is made with the formulation of a New Voltage Stability Index (NVSI) which originates from the equation of a two bus network, neglecting the resistance of transmission line, resulting in appreciable variations in both real and reactive loading. The efficacy of the index and fuzzy based load flow are validated with IEEE 30 bus and Tamil Nadu Electricity Board (TNEB) 69 bus system, a practical system in India. The results could prove that the identification of weak bus and critical line in both systems is effectively done. The weak area of the practical system and the contingency ranking with overloading either line or generator outages are found by conducting contingency analysis using NVSI.

• 대한기계학회논문집
• /
• 제14권6호
• /
• pp.1669-1678
• /
• 1990

본 연구에서는 다중선회연소기의 원리에 기초하여 연료와 산화제의 접촉면적 및 혼합속도를 증가시킴으로써 연소부하의 증대 및 연소효율의 향상효과를 얻을 수 있 는 새로운 연소방식을 개발하기 위한 시도로서 속도차가 있는 동축의 두 공기분류 사 이의 전단층에 기체연료를 분출시켜서 형성되는 난류확산 화염에 관하여 유동장의 성 상이 화염안정한계 및 화염구조에 미치는 영향을 조사하여 실용연소기의 유도장제어 및 고부하연소기설계를 위한 기초자료를 얻는데 목적이 있다.

• 한국소음진동공학회논문집
• /
• 제20권3호
• /
• pp.215-222
• /
• 2010

Long and slender body, like a fuel rod, oscillating in axial flow can be unstabilized even by the small cross flow which can be activated by the flow mixer or turbulent generator. It is important to include these effects of flow disturbance in dynamic stability analysis of nuclear fuel rod. This work shows how eigen frequency of a multi-span fuel rod can be changed by the swirl flow, which is discretely generated by a flow mixer. By solving a state-space form of the eigenvalue equation for a multi-span fuel rod system, the critical velocity at which a fuel rod becomes unstable was calculated. Based on the simulation results, we evaluated how stability of a multi-spanned nuclear fuel rod with mixing vanes can be affected by the coolant flow in an operating reactor core.