• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
• /
• pp.697-700
• /
• 2003

This paper presents design and analysis of step-down piezoelectric transformer for application to AC-adapters. These transformers are consist of rectangular type and disk type multilayered piezoelectric ceramic plate. This piezoelectric transformer operated in third thickness resonance vibration mode. Finite element methode(FEM) was used for analysing transformer. Vibration mode and electric field of piezoelectric transformer were simulated at resonance frequency. As results, rectangular type transformer's output voltage was higher than the disk type. But disk type transformer's current was lagger than rectangular type. These results are assumed that disk type transformer's mixed vibration mode influence transformer's output characteristics. From these results, we expect that disk type piezoelectric transformer is more adoptable than rectangular plate type piezoelectric transformer for AC adapters.

• 한국공작기계학회논문집
• /
• 제14권4호
• /
• pp.61-68
• /
• 2005

As a new approach to analyze grinding energy, this paper introduces a specific grinding energy model based on the average grain. Using this model, grinding characteristics such as radial and tangential forces, specific grinding energy of SM45C were investigated with changing grinding variables such as workpiece velocity(v) and apparent depth of cut(Z) in down-surface grinding. From the experimental results, the specific grinding energy decreases as the maximum undeformed chip thickness increases. And there is no significant difference between the specific grinding energies of the existing and the proposed model.

• 멤브레인
• /
• 제7권3호
• /
• pp.123-130
• /
• 1997

휴대용 정보 통신기기의 소형 경량화에 적합한 고용량 전지인 리튬이온 이차전지에 응용되는 미세다공성 고분자 격리막에 관한 특성을 검토하였다. 격리막으로서 요구되어지는 항목은 전지 성능에도 관련되며, 안전에도 관련된 것들 이어서, 전지의 부재로서 상당히 중요한 부분을 차지하고 있다. 철재는 폴리에틸렌(PE) 등과 같은 폴리올레핀 소재를 연신하여 제조한 미세다공성 격리막이 주로 채용되고 있으며, 다양한 shut-down온도에 적용 가능하고, wettability가 향상된 미세다공성 격리막으로서, 불소계 고분자의 적용 및 폴리올레핀계 소재의 표면개질 등에 관한 연구가 지속되고 있다.

• International journal of advanced smart convergence
• /
• 제6권4호
• /
• pp.1-8
• /
• 2017

In this work, the effects of fairly influential factors on performance of vacuum system, such as constant pressure and outgassing effect were simulated to propose the optimum design factors. Outgassing effects of selected vacuum materials on the vacuum characteristics were simulated by the $VacSim^{Multi}$ simulation tool. This investigation examined the feasibility of reliably simulating the outgassing characteristics of common vacuum chamber materials (aluminum, copper, stainless steel, nickel plated steel, Viton A). The optimum design factors for vacuum systems were suggested based on the simulation results. And, the effects of throttle valve applications on vacuum characteristics were also simulated to obtain the optimum design model of variable conductance on high vacuum system. Simulated vacuum characteristics of the proposed modelling were agreed with the observed experimental behaviour of real systems. Pressure limit valve and normally on-off control valve were schematized as the modelling of throttle valve for the constant process-pressure. Simulation results were plotted as pump-down curve of chamber and variable conductance of throttle valve. Simulated behaviors showed the applications of throttle valve sustained the process-pressure constantly, stably, and reliably.

• 한국자동차공학회논문집
• /
• 제6권4호
• /
• pp.219-227
• /
• 1998

This paper describes the fuel spray characteristics of gasoline port injectors such as the breakup procedures of liquid fuel, breakup and extinction behaviors of fuel spray at nozzle tip, time history of SMD and velocity distribution of fuel spray in the direction of fuel stream. Pintle-type gasoline fuel injector was used to analyze mentioned spray characteristics. In order to visualize the fuel spray behaviors and to measure the droplet mean diameter and velocities of spray droplets, the Schlieren method, digital image processing and auto-correlation PIV were applied in this study. In addition, the spray characteristics according to the variation of time were considered. The results of fuel spray show that the liquid sheet breakup starts at 10mm downstream actively. The flying time is approximately 4msec between 50mm and 80mm down the nozzle tip. Also, SMD of fuel spray, the number of droplets and fuel velocity distribution at each point of downstream are discussed.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.68-70
• /
• 2006

This paper formulates the principle of the magnetic actuator break system (MASS) for emergency situation driving a car. When the exciting break system of a car is broken, MASS will be able to stop the car by the electric system. MASS controls the rotating wheel to slow down gradually while holding and laying the wheel down several ten times per second. We present the magnetic field and dynamic behavior analyses for the magnetic actuator break system using finite element method (FEM) associated with parameter, for calculating the displacement of the moving parts and the supplying current.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
• /
• pp.683-686
• /
• 1998

In this paper, the power factor correction (PFC) system for inverter air-conditioner that has not only good harmonic characteristics but also cost down-merit compared with the conventional inverter type is proposed. The detail design procedures to get cost-down merits are introduced. And it is shown that the PFC system performances also can be improved by the virtue of the stabilization of output voltage. The proto type system is implemented and tested to virify the additional good performances of the proposed system, and its simulation and experimental results are presented.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2003년도 봄 학술발표회 논문집
• /
• pp.411-416
• /
• 2003

As rapid industrialization continues in these days, construction in the down town areas increases. Since constructions are performed around old and existing structures, the need to provide reinforcements to protect the existing structures from collapse and damage arises. Furthermore, if the construction is to take place in the down town area, difficult work space and damage caused by noise, vibration and collapse of structure can't be ignored. Among the remedial measures available today, micropile reinforcement is considered the best method to remedy these problems. But up to the present the characteristics of micropiles and ground behaviour has not been proven and no standard design is not yet available. Therefore, most design are performed based on previous experiences. In this study, the difference in the bearing capacity with changing reinforcement angle, space and sphere around foundation was monitored. These results were induced to broaden heighten the limits of micropile application.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 1999년도 제30회 추계학술대회
• /
• pp.179-183
• /
• 1999

Rubbing occurs when a rotating element comes in contact with a stationary element. In the steam turbines, the rotating element is the rotor while the stationary elements are usually the oil deflectors and packing seals. Rubbing phenomenon may be often obseued on a new or rebuilt machine rather than on a machine that has been operating for several months or years. Rubbing in the turbine has been classified into two modes by the operating conditions: 1) start up or shut down, 2) steady state. At start up or shut down operation, rubbing produces synchronous whirl vibration, which are caused by thermal bow of the shaft due to localized heating on the shaft surface. While subsynchronous whirl vibration is caused by partial rubbing during the steady state operation. In this paper, the two case studies of troubleshooting for excessive vibration caused by rubbing in the actual steam turbines are investigated.

• 한국연소학회지
• /
• 제5권2호
• /
• pp.63-68
• /
• 2000

Combustion phenomenon in scale-downed combustor is investigated. As the combustor scale decreases surface to volume ratio increases and chamber size approaches quenching distance. As the combustor scales down surface to volume ratio increases resulting increased heat loss. And this heat loss can affect quenching and instability of the flame. To investigate this effect plastic mini combustor is made. Stoichiometricaly premixed Hydrogen / air gas is used as fuel. Initial chamber pressure and chamber size are varied and the effects are evaluated. Peak pressure decreased with the decrease in chamber height. As initial chamber pressure decreases peak pressure decreases and this change is more important than scale down effect till the chamber height of 1mm. With this result and further information following the experiments design parameter for micro engine can be established.