• 대한기계학회논문집B
• /
• 제26권7호
• /
• pp.959-965
• /
• 2002

It is intended to develop an algorithm for dynamic simulation of a fast-acting solenoid valve. The coupled equations of electric, magnetic, and mechanical systems should be solved simultaneously in a transient nonlinear manner. The transient nonlinear electromagnetic field is analyzed by the Finite Element Method (FEM), which is coupled with nonlinear electronic circuitry. The dynamic movement of the solenoid valve is analyzed at every time step from the force balance acting on the plunger, which includes the electromagnetic force calculated from the Finite Element analysis as well as the elastic force by a spring and the hydrodynamic pressure force along the flow passage. Dynamic responses of the solenoid valves predicted by this algorithm agree well with the experimental results including bouncing effects.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2002년도 추계학술대회 논문집
• /
• pp.149-154
• /
• 2002

A simplified 3D dynamic model of tracked vehicle crawling on cohesive soft soil is investigated. The vehicle is assumed as rigid body with 6-dof. Cohesive soft soil is modeled through relations: pressure to sinkage, shear displacement to shear stress, and shear to dynamic sinkage. Equations of motion of vehicle are derived with respect to the body-fixed coordinates. In order to investigate 3D transient dynamics of tracked vehicle, Newmark's method is employed based on incremental-iterative algorithm. 3D dynamic simulations are conducted for a tracked vehicle model and steering performance is investigated.

• 대한전기학회논문지:전력기술부문A
• /
• 제54권9호
• /
• pp.441-448
• /
• 2005

On-line dynamic security assessment is becoming more and more important for the stable operation of power systems as load level increases. The necessity is getting apparent under Electricity Market environments, as operation of power system is exposed to more various operating conditions. For on-line dynamic security assessment, fast transient stability analysis tool is required for contingency selection. The TEF(Transient Energy Function) method is a good candidate for this purpose. The clustering of critical generators is crucial for the precise and fast calculation of energy margin. In this paper, we propose a new method for fast decision of mode of instability by using stability indices. Case study shows very promising results.

• International Journal of Precision Engineering and Manufacturing
• /
• 제1권2호
• /
• pp.67-75
• /
• 2000

virtual computer numerical control(VCNC) arises from the concept that one can experience pseudo-real machining with a computer-numerically-controlled(CNC) machine before actually cutting an object. To achieve accurate VCNC, it is important to determine abnormal behavior, such as chatter, before cutting. Detecting chatter requires an understanding of the dynamic cutting force model. In general, the cutting process is a closed loop system the consists of structural and cutting dynamic. Machining instability, namely chatter, results from the interaction between these two dynamics. Several previous reports have predicted stability for a single path, using a simple cutting force model without run out and penetration effects. This study considers both tool run out and penetration effects, using experimental modal analysis, to obtain predictions that are more accurate. The machining stability during a corner cut, which is a typical transient cut, was assessed from an evaluation of the cutting configurations at the corner.

• 전기학회논문지
• /
• 제58권1호
• /
• pp.93-99
• /
• 2009

In this paper, transient voltage response of Polmer Electrolyte Membrane Fuel Cell (PEMFC) stack is analyzed and voltage dynamic characteristic is modeled for optimal design of power conditioning system (PCS). According that the load is changed, the corresponding operating voltage of fuel cell stack is also varied with a certain deep and rising time due to the chemical and mechanical responses. This transient behavior can affect on the operation with respect of PI gain in controller, duty ratio, capacitor of capacitor and so on. So in this paper the detailed theoretical analysis of transient voltage dynamics is explained and the methodology of dynamic modeling is introduced. In addition, the validity and feasibility of the proposed dynamic model is verified by experimental results under various load conditions.

• 한국전산구조공학회논문집
• /
• 제14권3호
• /
• pp.349-359
• /
• 2001

본 논분은 평판구조물의 동적 시간이력해석을 수행하기 위하여 개발된 사절점 판요소에 대하여 기술하였다. 이 요소는 두꺼운 판에서 발생하는 횡전단 변형효과를 고려하기 위하여 Reissner-Mindlin(RM)가정을 도달하였다. 알려진 바와 같이 RM가정을 바탕으로 개발된 판요소가 얇은 판에 적용되면 전단강성 과대현상(,Shear Locking Phenomenon)을 일으키는데 이를 개선하기 위하여 본 연구에서는 가변형도법을 이용한 대체변형도를 자연좌표계에 준하여 명시적으로 유도하였다. 개발된 저차 판요소는 중앙 차분법을 이용한 명시적인 동적 해석 알고리즘에 적용되었으며 이때 판의 대각질량행렬은 특별집중질량법을 사용하여 형성하였다. 개발된 판의 성능은 수치예제를 통하여 평가하고 검증하였다.

• Structural Engineering and Mechanics
• /
• 제90권4호
• /
• pp.417-428
• /
• 2024

Nanocomposite-reinforced concrete systems have gained increasing attention in bridge construction due to their enhanced mechanical properties and durability. Understanding the transient dynamics of these advanced materials is crucial for ensuring the structural integrity and performance of bridge infrastructure under dynamic loading conditions. This paper presents a comprehensive study of the measurement techniques employed for assessing the transient dynamics of nanocompositereinforced concrete systems in bridge construction applications. A numerical method, including modal analysis are discussed in detail, highlighting their advantages, limitations, and applications. Additionally, recent advancements in sensor technologies, data acquisition systems, and signal processing techniques for capturing and analyzing transient responses are explored. The paper also addresses challenges and opportunities in the measurement of transient dynamics, such as the characterization of nanocomposite-reinforced concrete materials, the development of accurate numerical models, and the integration of advanced sensing technologies into bridge monitoring systems. Through a critical review of existing literature and case studies, this paper aims to provide insights into best practices and future directions for the measurement of transient dynamics in nanocompositereinforced concrete systems, ultimately contributing to the design, construction, and maintenance of resilient and sustainable bridge infrastructure.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
• /
• pp.62-69
• /
• 1996

Most dynamic systems have various random properties in excitation and system parameters. In this paper, a procedure fur response analysis is proposed for the linear dynamic system with random properties in both excitation and system parameters. The system parameter and response with random properties are modeled by perturbation technique, aand then response analysis is formulated by probabilistic and vibration theories. And probabilistic FEM is also used for the calculation of mean response which is difficult by the proposed response model. As an application example, the transient response is calculated for a sdof system with random mass and spring constant subjected to stationary white-noise excitation and the results are compared to those of numerical simulation.

• 설비공학논문집
• /
• 제21권12호
• /
• pp.695-702
• /
• 2009

Dynamic behavior of Libr-water absorption system using low-temperature hot water was investigated numerically. Thermal-hydraulic model of single-effect/double-lift 100 RT chiller was developed by applying transient conservation equations of total mass, Libr mass, energy and momentum to each component. Transient variations of system properties and transport variables were analysed during start-up operation. Numerical analysis were performed to quantify the effects of bulk concentration and part-load operation on the system performance in terms of cooling capacity, coefficient of performance, and time constant of system. For an absorption chiller considered in the present study, optimum bulk concentration was found to exist, which resulted in the minimum time constant with stable cooling capacity. COP and time constant increased as the load decreased down to 40%, below which the time constant increased abruptly and COP decreased as the load decreased further.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2005년도 춘계학술대회
• /
• pp.353-356
• /
• 2005

We developed a dynamic model of PEM fuel cell system which can analyze its transient response to dynamic load current. System components such as compressor, air cooler, humidifier, and stack were modeled based on their dynamic equations and performance maps by using Matlab Simulink platform. Through this simulation model, dynamic characteristics of fuel cell system including oxygen excess rat io, stack voltage, and system efficiency were shown. In addition to that, we briefly analyzed the humidity effect on cathode pressure and system efficiency, expecting that this model can be further used to optimize fuel cell system parameters just like operating pressure and temperature, humidity and oxygen excess ratio.