• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2010년 춘계학술대회논문집
• /
• pp.93-98
• /
• 2010

One of the most effective key factors to improve performance of automotive reciprocating compressor is the design of suction and discharge reed valves. Reed valves are also the major sources of compressor noise. Valve motion is highly coupled with refrigerant flow. In this study, a process of fluid-structure interaction analysis was developed to predict the cylinder inner flow and the dynamic behavior of valve simultaneously. Interface programs computational structural dynamics code. The full cycle simulations of compressor were performed using FSI analysis was alidated by comparing the simulation results with the experimental results.

• 소음진동
• /
• 제6권4호
• /
• pp.475-479
• /
• 1996

Recently, fiber optic hydrophone is a subject which has attracted as a underwater acoustic sensor. In this paper, a length of optical fiber is bonded to an end-capped hollow cylinder of some elastic material, e. g. aluminum and glass-pyres. The normalized sensitivity is derived according to the direction of polarization. Derived sensitivity equations are simulated for two different mandrel materials. The results are also compared to the McMahon's results which calculated for an average Pockel coefficient. Based on the numerical simulation normalized sensitivity is propotional to the inner to outer diameter ratio.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2010년도 춘계학술대회 논문집
• /
• pp.816-822
• /
• 2010

A comprehensive review for the selection of urban rail vehicle systems that best suit Gimpo railway line is taking place with consideration of the project area characteristics in light of line planning, passenger demand, supply of rolling stock, and railway construction and operation. Various aspects of vehicle systems including passenger demand on concerned lines, regional characteristics, vehicle types, and railway construction and operational settings should be taken into consideration. In addition, request for the introduction of customized vehicle systems reflecting the convenience of transit users such as wide and hospitable inner space, low noise, flexible operation of 2 to 4 car train-set and eye catching slim bridge piers is increasing. A study on alternatives to place an order to opt for optimum rolling stock systems considering line characteristics of Gimpo City's urban railway and future passenger demand while meeting the needs of Gimpo City has been conducted.

• 한국멀티미디어학회논문지
• /
• 제20권2호
• /
• pp.108-114
• /
• 2017

Lip reading is a field of image processing to assist the process of sound recognition. In some environment, the capture of sound signal usually has significant noise and therefore, the recognition rate of sound signal decreases. Lip reading can be a good feature for the increase of recognition rates. Conventional lip extraction methods have been proposed widely. Maia et. al. proposed a method by the sum of Cr and Cb. However, there are two problems as follows: the point with maximum saturation is not always regarded as lips region and the inner part of lips such as oral cavity and teeth can be classified as lips. To solve these problems, this paper proposes a method which adopts the histogram-based classifier for the extraction of lips region. The proposed method consists of two stages, learning and test. The amount of computation is minimized because this method has no color conversion. The performance of proposed method gives 66.8% of detection rate compared to 28% of conventional ones.

• 정보저장시스템학회논문집
• /
• 제8권1호
• /
• pp.27-32
• /
• 2012

Fluid dynamic bearings have several advantages that low noise, high rotational stability and low friction. So, early 2000s, the HDD spindle motors have been replaced ball bearings to fluid dynamic bearing. Most of studies apply inner boundary condition that is inside of bearing pressure larger than atmosphere pressure. Therefore, they used Half-Sommerfeld or Reynolds Boundary condition. This paper investigates the dynamic coefficients of the plain journal considered vapor pressure. As a result, it shows that the vapor pressure effect cannot ignore.

• 한국방송∙미디어공학회:학술대회논문집
• /
• 한국방송공학회 2012년도 추계학술대회
• /
• pp.188-190
• /
• 2012

Compressed Sensing (CS) has been developed for several years. Among many CS algorithms for image, the Block-based Compressed Sensing with Smoothed Projected Landweber (BCS-SPL) demonstrates its excellent performance in low-complexity and near-optimal reconstruction. Several noise filtering algorithms of image reconstruction have been introduced such as the Wiener or the median filters, etc. In general, each filter has its own advantages and disadvantages depending on specific coding scheme. In this paper, we show that reconstruction performance can be varied according to the choice of filter. When a sub-rate value is changed, different filter causes different effect as well. Concerning the sub-rate, an inner filter can be chosen to improve the reconstructed image quality.

• 한국자동차공학회논문집
• /
• 제20권2호
• /
• pp.141-147
• /
• 2012

Engine mount is used to soften the impact of bumper with elasticity recovery and damping capacity. Inner noise and vibration to influence the comfortableness for passenger cause the engine to the chattering phenomenon. In this study, structural analysis can be done by engine mounts designed with 3D modelling. Natural frequencies and harmonic responses are analyzed by using models with some kinds of configurations. When the simulation model is applied by the force of 600N within the range of natural frequencies, the magnitude of deformation becomes 0 to 3mm. As the number of holes around inside mount increases, the capability of vibration absorption and durability becomes larger. In case of 5holes around inside mount, it can be safest on durability. The life of mount becomes larger by changing the configuration of model. The engine mount improved with durability can be designed through the result of simulation.

• 반도체디스플레이기술학회지
• /
• 제6권1호
• /
• pp.31-36
• /
• 2007

Effect of coulomb friction and backlash on the single loop position control has been studied for the precision position control. We have showed the limit cycle on the single loop system which used a ball screw that had the backlash. Also, we have made an inner loop with a classical velocity and torque controller which was forcing the current of d axis to be zero by using a permanent-magnet synchronous motor and composed the outer loop with linear encoder for sensing a position of the loader. Also, we have used least squares fit(LSF) observer for reducing noise when we got velocity from position outputs. We have shown a good result by using the dual loop through simulation and experiment.

• 통합자연과학논문집
• /
• 제13권1호
• /
• pp.1-7
• /
• 2020

This paper proposes a novel fractional frequency reuse(FFR) based on dynamic user distribution. In the FFR, a macro cell is divided into two regions, i.e., the inner region(IR) and outer region(OR). The criterion for dividing the IR and OR is the distance ratio of the radius. However, these distance-based criteria are uncertain in measuring user performance. This is because there are various attenuation phenomena such as shadowing and wall penetration as well as path loss. Therefore, we propose a novel FFR based on dynamic user classification with signal to interference plus noise ratio(SINR) of macro users and classify the FFR into two regions newly. Simulation results show that the proposed scheme has better performance than the conventional FFR in terms of SINR and throughput of macro cell users.

• 정보학연구
• /
• 제10권4호
• /
• pp.27-39
• /
• 2007

Object tracking in a real time environment is one of challenging subjects in computer vision area during past couple of years. This paper proposes a method of object detection and tracking using adaptive background estimation in real time environment. To obtain a stable and adaptive background, we combine 3-frame differential method and running average single gaussian background model. Using this background model, we can successfully detect moving objects while minimizing false moving objects caused by noise. In the tracking phase, we propose a matching criteria where the weight of position and inner brightness distribution can be controlled by the size of objects. Also, we adopt a Kalman Filter to overcome the occlusion of tracked objects. By experiments, we can successfully detect and track objects in real time environment.