• Advances in environmental research
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• v.6 no.1
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• pp.53-65
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• 2017

Assessment of seasonal changes in surface water quality is an important aspect for evaluating temporal variations of river pollution due to natural or anthropogenic inputs of point and non-point sources. In this study, surface water quality data for 15 physico-chemical parameters collected from 7 monitoring stations in a river during the years from 2014 to 2016 were analyzed. The principal component analysis technique was employed to evaluate the seasonal correlations of water quality parameters, while the principal factor analysis technique was used to extract the parameters that are most important in assessing seasonal variations of river water quality. Analysis shows that a parameter that is most important in contributing to water quality variation for one season may not be important for another season except alkalinity, which is always the most important parameters in contributing to water quality variations for all three seasons.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.998-1012
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• 2013

The article is concerned with a mathematical modeling which can improve performances of PDE-based restoration models. Most PDE-based restoration models tend to lose fine structures due to certain degrees of nonphysical dissipation. Sources of such an undesirable dissipation are analyzed for total variation-based restoration models. Based on the analysis, the so-called equalized net diffusion (END) modeling is suggested in order for PDE-based restoration models to significantly reduce nonphysical dissipation. It has been numerically verified that the END-incorporated models can preserve and recover fine structures satisfactorily, outperforming the basic models for both quality and efficiency. Various numerical examples are shown to demonstrate effectiveness of the END modeling.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.4
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• pp.371-374
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• 2012

DC/DC switching power converters produce DC output voltages from different stable DC input sources regulated by a bi-polar transistor. The converters can be used in regenerative braking of DC motors to return energy back in the supply, resulting in energy savings for the systems containing frequent stops. The voltage mode DC/DC converter is composed of a PWM (Pulse Width Modulation) controller, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), an inductor, and capacitors, etc. PWM is applied to control and regulate the total output voltage. It is shown that the output of DC/DC converter depends on the variation of threshold voltage at MOSFET and the variation of pulse width. In the PWM operation, the missing pulses, the changes in pulse width, and a change in the period of the output waveform are studied by SPICE (Simulation Program with Integrated Circuit Emphasis) and experiments.

• Transactions on Electrical and Electronic Materials
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• v.8 no.1
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• pp.11-14
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• 2007

Consumables used in Chemical Mechanical Polishing (CMP) have been played important role to improve quality and productivity. Since the properties of consumables constantly change with various reasons, such as shelf time, manufactured time, lot to lot variation from supplier and so on, CMP results are not constant during the process. Also, CMP process results are affected by multiple sources from wafer, conditioner, pad and slurry. Therefore, multiple sensing systems are required to monitor CMP process variation. In this paper, the authors focus on development of monitoring system for CMP process which consist of force, temperature and displacement sensor to measure the signal from CMP process. With monitoring systems mentioned above, complex CMP phenomena can be investigated more clearly.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.4
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• pp.42-50
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• 2003

This paper presents an embedded RC oscillator which has temperature compensation circuits. The conventional RC oscillator has frequency deviation about 15%, which is caused by variation of resistors and the reference voltage of schmitt trigger from the temperature condition. In this paper, the proposed circuit use a CMOS bandgap reference having balanced current temperature coefficients as a triggering voltage of schmitt trigger. The constant current sources consist of current mirror circuit with the positive and negative temperature coefficient. The proposed circuit shows less 3% frequency deviation for variation of temperature, supply voltage and process parameters.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.6
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• pp.546-552
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• 2016

We present a quantitative evaluation of an algorithm for model-based face recognition. The algorithm actively learns how individual faces vary through video sequences, providing on-line suppression of confounding factors such as expression, lighting and pose. By actively decoupling sources of image variation, the algorithm provides a framework in which identity evidence can be integrated over a sequence. We demonstrate that face recognition can be considerably improved by the analysis of video sequences. The method presented is widely applicable in many multi-class interpretation problems.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.207-210
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• 2002

In this paper, We have measured the luminous flux variation of electrodeless fluorescent lamp system reducing a power source to 70% and applying a short interruption caused by the power failure. So we can understood that the protective device for apparatus of power sources is important thing to control electrodeless fluorescent lamp system.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.6 no.1
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• pp.29-35
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• 2010

Long-term temperature monitoring has been performed for ground heat exchanger at the Earthquake Research Center (ERC) building in Korea Institute of Geoscience and Mineral Resources (KIGAM). For the 3 years of monitoring, overall temperature increases are observed at various depths within a borehole heat exchanger. But monitoring of ground temperature variation at the monitoring well beforehand showed that geothermal utilization is not the only source for the temperature increase, Because various kinds of sources can cause the ground temperature change, more thorough investigation should be followed.

• Journal of Ocean Engineering and Technology
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• v.9 no.2
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• pp.71-74
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• 1995

A numerical model capable of simulating a 2-D airfoil flying over in the vicinity of the waves is discussed. Instead of treating the problem as a heaving oscillation one above the rigid flat wall, sources are distributed on the prescribed wave profile. The wave deformation due to the airfoil is assumed to be negligible and treated as a rigid undulated wall. The source and vortex are distributed on the surface of the foil. It is found that the variation of $C_L$ with wave steepness in severe and that the lift variation due to waves decreases as the wing height above the water surface increases.

• Journal of Environmental Science International
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• v.10 no.3
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• pp.187-194
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• 2001

For the purpose of predicting air pollutants concentration in Pusan coastal urban, we used an Eulerian model of flow and dispersion/chemistry/deposition process considering SST effects which estimate through POM. The results of air quality model including emission from various sources show that the seasonal variation pattern of respective pollutants was affected by the seasonal SST fields and local circulation. Horizontal deviation of diurnal SST was 2.5~4K, especially large gradients in coastal region. Through numerical simulation of wind fields we predicted that local circulation prevailed during daytime in summer and nighttime in winter. So high concentration distribution showed toward inland in spring and summer seasons, while high concentration distribution showed at inland near coast in autumn and winter.