• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.2
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• pp.134-139
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• 2008

To improve the oxygen-deficient water mass (ODW), the spatial and temporal variation in the water quality and characteristic of ODW occurrence were analyzed using yearly water quality data from 1989 to 2006 in Jinhae Bay, Korea. In addition, we estimated $ODW_{area},\;ODW_{vol.}$ and $ODW_R$ for Jinhae Bay. The overall water quality improved during the 2000s, based the annual variation in dissolved oxygen, chemical oxygen demand, etc. A cluster analysis classified Jinhae Bay into the southwestern, central, northern, and eastern regions. ODW occurred throughout the southwestern region in 1993 and 2002-2004, and the estimated $ODW_{vol.}$ was about $1.92km^3$. ODW did not occur in the eastern region because circulating seawater was exchanged in that part of Jinhae Bay. As ODW was generated every year in the southwestern region, this is the most polluted area in Jinhae Bay. The ODWR decreased in the northern region, showing that the water quality there has improved since a wastewater treatment plant began operating in 1994.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.7
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• pp.98-105
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• 2020

This study deals with the passive control of the dynamic characteristics of a theoretical model which is a string with fixed ends and loaded by two point masses - a main mass (M_o) and a secondary mass (M_s). It has been controlled passively by means of a relocation of a secondary mass. A main mass placed on the string is considered as a vibrating receiver which be forced to vibrate by a vibrating source being positioned on the string. By analyzing the motion of a string, the equation of motion for a string was derived by using a method of variation of parameters. To define the optimal conditions for the vibration reduction, the governing equation, which denotes the dynamic response of a string was derived in the closed form and then evaluated numerically. The possibility of reduction of an amplitude and a power being transmitted to a main mass were found to depend on the location and the magnitude of a secondary mass as well as the range of a forcing frequency.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.120-125
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• 2004

In the rolling of steel or non-steel metal the most important quality aspect are thickness and flatness. In thickness, there are two important factors. One of them is getting close with accurate goal, nominal gauge, the other is minimize gauge bandwidth, the variation in gauge. In this thesis, we proposed the fuzzy model AGC to minimize gauge variation along the length, developed the rolling mill dynamic model using the math mode of the rolling mill process and the rolling model related with the variety character of the rolling material. We compared the gauge control efficiency of fuzzy model AGC and PI mass flow AGC. We have got a simulation result, that the exit gauge variation of PI mass flow AGC was 2 micron and fuzzy model AGC was 1.2 micron at 1200mpm of rolling speed when each controller was rolling 5 micron of material that is the entry gauge variation.

• Journal of The Korean Astronomical Society
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• v.46 no.4
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• pp.151-159
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• 2013

We discuss the orbital period changes of the Algol semi-detached eclipsing binary DI Peg by constructing the (O-C) residual diagram via using all the available precise minima times. We conclude that the period variation can be explained by a sine-like variation due to the presence of a third body orbiting the binary, together with a long-term orbital period increase (dP/dt=0.17 sec/century) that can be interpreted to be due to mass transfer from the evolved secondary component (of rate $1.52{\times}10^{-8}M_{\odot}/yr$) to the primary one. The detected low-mass third body ($M_{3min.}=0.22{\pm}0.0006M_{\odot}$) is responsible for a periodic variation of about 55 years light time effect. We have determined the orbital parameters of the third component which show a considerable eccentricity $e_3=0.77{\pm}0.07$ together with a longitude of periastron ${\omega}_3=300^{\circ}{\pm}10^{\circ}$.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.221-229
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• 1996

The engine speed fluctuation at idle operation mainly comes from cyclic variation of combustion in SI engine. In the present study, engineering model that is representing the cyclic variation of combustion was proposed for the sub-model of the engine cycle simulation. From the observed behaviors of the mass burn rates, probability density functions for the parameters of Wiebe function were defined. The mass burn rate of each cycle is obtained by Monte Cralo perturbation method with the probability function. The simulation results shows that trends of cylinder pressure variation and imep distribution follow up with those of experimental results at idle condition.

• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.413-421
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• 2022

Modal parameters are the main dynamic characteristics of bridge. This study aims to propose an innovative route to estimate the modal parameters for bridges by using a parked vehicle in which mode shapes with high accuracy and spatial resolution are identified by frequency measurement. Based on the theory of dynamic modification and modal identification, the mathematical formulation between the parked mass induced frequency variation and the modal parameters of a bridge is derived. Then this mathematical formulation is extended to a parked vehicle-bridge system. The arithmetic and processes for estimating the modal parameters based on the identified frequency variation of the vehicle-bridge systems when the vehicle locates at sequentially arranged positions are presented. Finally the proposed method is applied to several simulated bridges of different types. The results indicate that it can estimate the modal parameters with high accuracy and efficiency.

• Journal of Theoretical and Applied Mechanics
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• v.1 no.1
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• pp.89-96
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• 1995

An analytical method is presented for predicting the effect of a local deviation in the form of a concentrated mass along a radial line on the free bending vibration characteristics of a nearly axisymmetric circular plate. The approach is based on the Rayleigh-Ritz method and the expression of local deviation of the concentrated radial mass as the variation of heaviside unit step function. The effects of the concentrated mass on the natural frequencies and mode shapes of the plate are predicted with a proposed nondimensional mass parameter.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.7
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• pp.428-436
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• 2005

In this paper, we introduce an adaptive control method to improve the position accuracy and reduce nonlinear friction effects for the linear motion servo system with the nonlinear friction. The considered system plant included not only the variation of the mass of mover but also the friction change by the normal force. We also designed an adaptive controller with the mass estimator and the compensator by observing the variation of normal force. The effectiveness and system performances for the proposed control method in this paper show to improve than other control methods through numerical simulations.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.2
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• pp.41-47
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• 1983

The analysis shows that the variation of maximum pressure of the cycle, rate of hear release, rate of mass burned, and combustion delay are influenced by the inlet air humidity in the spark-ignition engine. The quantitative combustion delay can be obtained from the rate of mass burned. Also, the variation of time loss and effective compression ratio with the change of inlet air humidity are dominated by the development of rate of heat release.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.152-156
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• 2007

It is very important to understand about mass flow rate variations of propellants generated by pressure fluctuation in the combustion chamber. Therefore, we have studied quantifying the variation of mass flow rate generated by pressure fluctuation. The flow velocity in orifice is acquired through theoretical approach after measuring the pressure in orifice and the flow area in orifice is measured by film thickness measuring device. Our results agreed with it in the very small error range comparing our results with velocity and mass flow rate in steady state. Thus, our result based on theoretical approach will help about measuring mass flow rate in non-steady state.