• 대한기계학회논문집B
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• 제20권1호
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• pp.284-294
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• 1996

In this paper, dynamic characteristics of an AT clutch system were investigated considering the dynamics of check ball and hydraulic control valves. Dynamic model of a pressure control solenoid valve (PCSV) was obtained by Bondgraph and permeance method. Also, the clutch piston and check ball dynamics were modeled by considering the effect of centrifugal force of the oil entrapped in the clutch chamber. In order to validate the dynamic models obtained, plunger displacement of PCSV and pressure response of the clutch supply lines were compared with the available experimental data, which were in good accordance with the numerical results. Using the dynamic model of the clutch system, simulations were performed to investigate the effect of the rotational speed on the response of clutch cylinder pressure, clutch piston and check ball displacement, and oil flow rate into the cylinder and flow rate out of the check valve.

• Journal of Communications and Networks
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• 제5권1호
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• pp.65-72
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• 2003

Internet roundtrip delay/time (RTT) prediction plays an important role in detecting packet losses in reliable transport protocols for traditional web applications and determining proper transmission rates in many rate-based TCP-friendly protocols for Internet-based real-time applications. The widely adopted autoregressive and moving average (ARMA) model with fixed-parameters is shown to be insufficient for all scenarios due to its intrinsic limitation that it filters out all high-frequency components of RTT dynamics. In this paper, we introduce a novel parameter-varying RTT model for Internet roundtrip time prediction based on the information theory and the maximum entropy principle (MEP). Since the coefficients of the proposed RTT model are updated dynamically, the model is adaptive and it tracks RTT dynamics rapidly. The results of our experiments show that the MEP algorithm works better than the ARMA method in both RTT prediction and RTO estimation.

• 한국레이저가공학회지
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• 제5권2호
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• pp.31-38
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• 2002

This paper describes the process of nanoparticle synthesis by laser ablation of consolidated microparticles. We have generated nanoparticles by high-power pulsed laser ablation of Al, Cu and Ag microparticles using a Q-switched Nd:YAG laser (wavelength 355 nm, FWHM 5 ㎱, fluence 0.8∼2.0 J/㎠). Microparticles of mean diameter 18∼80 ㎛ are ablated in the ambient air The generated nanoparticles are collected on a glass substrate and the size distribution and morphology are examined using a scanning electron microscope and a transmission electron microscope. The effect of laser fluence and collector position on the distribution of particle size is investigated. The dynamics of ablation plume and shock wave is analyzed by monitoring the photoacoustic probe-beam deflection signal. Nanosecond time-resolved images of the ablation process are also obtained by laser flash shadowgraphy. Based on the experimental results, discussions are made on the dynamics of ablation plume.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 추계학술대회 논문집
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• pp.550-557
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• 1999

Results of the dynamic simulation on KTX catenary and catenary-pantograph interface are presented. Simulation programs based on finite element and finite difference models of the catenary are developed, while the pantograph is modeled as a linear 3-degree-of-freedom system. The catenary motion dynamics are primarily determined by the transmission and reflection of the propagating disturbance wave at the hanger and span boundaries. On the other hand, the catenary-pantograph contact characteristics are primarily influenced by the movement of the pantograph across the hanger and span boundaries, the amount of damping present in the contact wire, and the resonant frequencies of the pantograph.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제27권2호
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• pp.123-134
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• 2023

Disordered eating behaviors, such as overeating, are known to be contagious in the general population. The objective of our research is to find an optimal control strategy to reduce the social burden of unhealthy overeating behavior by establishing and analyzing a mathematical model for the social transmission dynamics of unhealthy overeating. We consider four compartments in the population: normal weight with normal eating behavior, normal weight with overeating behavior, overweight with normal eating behavior, and overweight with overeating behavior. Simulation results under various control scenarios show that integrated control measures may be necessary to reduce the growth rate of the overeating population.

• 한국생산제조학회지
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• 제21권4호
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• pp.582-587
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• 2012

Recently, the low-emissivity glass has been used to reduce the energy loss through building windows. However, it simply reduces the inflow of solar rays and has a relatively high heat transmission coefficient. To solve the problems, a high-efficiency vacuum glazing has been under development but it has not been actively used due to its high price and insufficient performance. In this paper, the effects of internal pressure, pillar (spacer) height, pillar diameter, pillar interval, emissivity etc. on the performance of vacuum glazing have been analyzed with three-dimensional computational fluid dynamics and structural analysis. As a result, the performance of vacuum glazing was predicted more accurately and major factors that determine the performance of vacuum glazing were optimized.

• Journal of Magnetics
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• 제20권4호
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• pp.460-465
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• 2015

The paper presents methodologies and results concerning one- and two-dimensional numerical modeling of radio frequency oscillations in a coaxial transmission line fed with a short pulse of electric current. The line is partially filled with a ferrite material, magnetized longitudinally close to saturation. The 2D model has permitted analyzing, for the first time in the art, the spatial structure and dynamics of the wave field within the radially non-uniform cross-section planes of the non-linear and dispersive guiding structure. This opens ways for optimizing size parameters of the line and the extent to which it is filled with the ferromagnetic material, thus increasing the line's electric strength and intensity of the r.f. oscillations.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1429-1436
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• 2000

Suction muffler is one of the important component of a compressor for low noise level and high efficiency. The suction muffler which has the complicated flow path gives the higher transmission loss of sound, but lower efficiency of compressor results from the superheating effect and flow loss in suction flow path. It is shown that the computational analysis of fluid dynamics are very popular methods for designing of high performance and low noise suction muffler. To reduce the thermodynamic and flow loss in suction process, the flow path of suction muffler was estimated by FVM(Finite Volume Method) and verified by experiments. And to enlarge the transmission loss of sound, the acoustic properties inside the suction muffler was analyzed by FEM(Finite Element Method) and experiments. The smart muffler which gives a good efficiency and low noise character was developed by using those methods, and the effect was evaluated in compressor by experiment.

• 제어로봇시스템학회논문지
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• 제4권6호
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• pp.722-728
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• 1998

In this paper real-time estimation methods for identifying the tire-road friction coefficient are presented. Taking advantage of the Magic Formula Tire Model, the similarity technique and the specific model for the vehicle dynamics, a reduced order observer/filtered-regressor-based method is proposed. The Proposed method is evaluated on simulations of a full-vehicle model with an eight state nonlinear vehicle/transmission model and nonlinear suspension model. It has been shown through simulations that it is possible to estimate the tire-road friction from measurements of engine rpm, transmission output speed and wheel speeds using the proposed identification method. The proposed method can be used as a useful option as a part of vehicle collision warning/avoidance systems and will be useful in the implementation of a warning algorithm since the tire-road friction can be estimated only using RPM sensors.

• Journal of Advanced Marine Engineering and Technology
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• 제33권5호
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• pp.713-720
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• 2009

Numerous applications of position controlling devices using servoing technique and transmission of energy through belt drives are practiced in the industry. Belt drive is a simple, lightweight, low cost power transmission system. Belt drives provide freedom to position the motor relative to the load and this phenomenon enables reduction of the robot arm inertia. It also facilitates quick response when employed in robotics. In this paper, precision positioning of a belt driven mechanism using a feed-forward compensator under maximum acceleration and velocity constraints is proposed. The proposed method plans the desired trajectory and modifies it to compensate delay dynamics and vibration. Being an offline method, the proposed method could be easily and effectively adopted to the existing systems without any modification of the hardware setup. The effectiveness of the proposed method is demonstrated through computer simulation and experimental results.