• 한국소음진동공학회논문집
• /
• 제24권2호
• /
• pp.102-107
• /
• 2014

The engine excitation forces are considered as major vibration source for the forklift truck, especially in small class. Even though the current engine mounting system designs are acceptable for vibration isolation, the performance of the engine mounting system is still required for the tendency of light weight, higher power and driver's higher vibration requirement. In this paper vibration reduction technique of forklift engine which is supported on rubber mounts is presented. Based on the dynamic model of resilient engine mounting system, design evaluation program is established. The design optimization technique and evaluation method of system properties are discussed. Effects of optimal design are validated through comparison with test results.

• 소성∙가공
• /
• 제20권1호
• /
• pp.5-10
• /
• 2011

The main objective of the present study is to predict the process window of injection-compression molding corresponding to the capability of an injection machine for fabricating 7 inch LGP. The open distance and volume filled after injection stage were found to be two important factors that affect critical requirements such as flow length, injection pressure and clamping force for the process. Process window for the key factors was also predicted by response surface method. As a result, predicted process window for open distance and volume filled after injection stage satisfying the critical requirement with a given injection machine was in the range of 60 ~ 75%, and 104.00 ~ 104.25%, respectively.

• 한국정밀공학회지
• /
• 제18권8호
• /
• pp.157-163
• /
• 2001

This paper presents the new linear notion device so called \"inch-werm\" which gets large displacement by incrementally summing small displacements of PZT actuators. Dynamic stiffness of inch-worm is generally low compared to its driving condition due to the requirement of inch-worm like small size and light weight. This low stiffness may degenerate the positional precision of inch-worm. An inch-worm is realized using three PZT actuators, a monolithic moving device and a guide way frame. Finite element method and experimental approach are used to analyse the static and dynamic motion of the designed inch-worm. Command reference input is shaped to reduce the residual vibration of inch-worm. The practical feasibility of inch-worm is also examined by running tests.ing tests.

• 한국통신학회논문지
• /
• 제38C권8호
• /
• pp.719-724
• /
• 2013

Visible light communication based wireless personal area network (WPAN) has recently remained in the center of attention, as it shows a lot of promise to a be a perfect replacement for the contemporary Radio frequency (RF) communication at least in the indoor environment. A commercially deployable VLC based WPAN must support diverse traffic requirement for different kinds of service. In this paper, we have proposed an innovative bandwidth allocation scheme for VLC based WPAN. We wish to allocate bandwidth adaptively for users in a network where bandwidth for each user is allocated scalably. Our aim is to allow maximum number of users in a VLC based WPAN where each user is guaranteed their required QoS. The simulation results justify that the proposed scheme is better than the conventional scheme.

• 한국정밀공학회지
• /
• 제33권10호
• /
• pp.789-796
• /
• 2016

The weight of an antenna system pointing satellite on the mobile platform is restricted by the weight limit of the mobile platform. The maximum power of the actuator driving the antenna system is thus limited because a high power actuator needs a heavier weight. Thus, a drive system is designed to have a low torque requirement by reducing the gravitational torque depending on gravity or acceleration of the mobile platform, including vibration, shock, and accelerated motion. To reduce the gravitational torque, the mathematical model of the gravitational torque is preferentially obtained. However, the method to directly estimate the mathematical model in an antenna system has not previously been reported. In this paper, a method is proposed to estimate the gravitational torque as a mathematical model in the antenna system. Additionally, a method is also proposed to calculate the optimal weight of the balancing weight to compensate for the gravitational torque.

• 한국기계가공학회지
• /
• 제2권1호
• /
• pp.69-74
• /
• 2003

The purpose of the present paper is to investigate about the machining of profile (core/cavity) of mold die using the commercial CAM system. Recently the requirement of the light weight and high performance of automobiles has Increased. The weight of the automobile is very important in the viewpoint of the fuel and traveling performance. The optimal design technique, material technique, the process design for parts and specially, die machining technique need to be developed for increasing productivity and reducing production time of the automobile parts. In this study, the effect of machining condition on precision of die profile is investigated by experimental observation and analysis. The results will be reflected for development of the precision die of the automobile.

• Journal of Power Electronics
• /
• 제9권3호
• /
• pp.403-409
• /
• 2009

Automatically tuned passive filters can improve power quality to a great extent in power systems. A novel three-phase shunt auto-tuned filter is designed to effectively compensate source current harmonics and to provide reactive power required by the non-linear load, which draws a highly reactive, harmonic-rich current from the supply. An artificial neural network (ANN) based controller selects filter component values in accordance with reactive power requirement and harmonic compensation. Traditional passive filters are permanently connected to the system and draw large amounts of source current even under light load conditions. By using auto-tuned filters, the passive filter components can be controlled according to load variations and, hence, draw only required source currents. The selection is done by the ANN with the help of a properly tuned knowledge base to provide instantaneous compensation using a digital controller.

• Journal of Communications and Networks
• /
• 제8권2호
• /
• pp.151-157
• /
• 2006

In a continuously expanding wireless world, the number of radio systems increases every day and efficient spectrum usage becomes a more significant requirement. Ultra-wideband (UWB) and cognitive radio are two exciting technologies that offer new approaches to the spectrum usage. The main objective of this paper is to shed the first light on the marriage of these two important approaches. The strength of orthogonal frequency division multiplexing (OFDM) based UWB in co-existing with licensed systems is investigated. The opportunity concept is defined, and the requirements of the opportunistic spectrum usage are explained. It is proposed to take the UWB-OFDM from the current underlay implementation, and evolve it to a combined underlay and opportunistic spectrum usage technology, leading to cognitive UWB-OFDM. This way, we aim at making UWB more competitive in the wireless market with extended range, higher capacity, better performance, and a wide variety of applications.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 춘계학술대회 논문집
• /
• pp.877-880
• /
• 2001

This paper presents the new linear motion device so called "inch-worm" which gets large displacement by incrementally summing small displacements of PZT actuators. Dynamics stiffness of inch-worm is generally low compared to its driving condition due to the requirement of inch-worm like small size and light weight. This low stiffness may degenerate the positional precision of inch-worm. An inch-worm is realized using three PZT actuators, a monolithic moving device and a guide way frame. Driving input signal is shaped to reduce the residual vibration of inch-worm by LQG controller and cycloid step input. The practical feasibility of inch-worm is also examined by running test.ning test.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 추계학술대회논문집B
• /
• pp.353-358
• /
• 2000

To achieve the requirement for high fuel economy and low emissions, the research for GDI engines is recently very brisk in the whole world. This study was performed to measure distribution of average particle size in non-evaporating spray. The 2-D fluorescence/scattering images of fuel spray were captured simultaneously by visualization system composed of a laser sheet, a doubling prism, optical filters, and an ICCD camera. Using the ratio of the two light intensities, particle size distribution was obtained. The SMD measured by fluorescence/scattering technique was compared with it obtained by PDA. The experimental results show that the spray structure of GDI injector and temporal SMD distribution.