• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.9
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• pp.8-17
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• 2012

This paper proposes high performance control of light emitting diode(LED) drive system for liquid crystal display(LCD) backlight. The CCFL(cold cathode fluorescent lamp)was used to a conventional LCD backlight. Due to improvement on luminous efficiency, long life and wide color gamut, LED has gradually substituted for CCFL as backlight. The backlight using LED is necessary to use many LED. For that reason, the LED backlight is using a lot of LED driving circuits. The many LED driving circuit is generated a current deviation between LED. Eventually, it is caused brightness deviation between LED. Therefore, this paper improves the current deviation using transformer and balancing capacitor to solve this problem. Also, for accurate and uniform brightness control, this paper is applied the artificial intelligent control to a dimming control. This paper is compared with conventional system, and validity of this paper proves through that result.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.6
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• pp.8-15
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• 2012

In this paper, we investigated possible optical parameters causing deviation of experimentally observed output spectra from theoretically predicted results in a high-order fiber comb filter based on a polarization-diversity loop configuration. They include wavelength dependency of half-wave plates (HWPs) inserted in the filter for wavelength switching and the modal birefringence of single-mode fibers (SMFs) with which optical components comprising the filter are connected. In order to consider the effect of the modal birefringence of the SMF on a filter performance, it is modeled as a low birefringence fiber with an arbitrary orientation angle and birefringence. It is found from the simulation results that the modal birefringence of SMFs strongly affects the spectral characteristics of the filter and decreases the extinction ratio of the filter, compared with the wavelength dependency of HWPs. In particular, it is also confirmed that the spectral deviation and asymmetric distortions of side-lobes in narrow band transmission spectra result mainly from the modal birefringence of SMFs.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.5
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• pp.26-32
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• 2013

The LED has the proportional characteristic between the flux of light and its current and has caused voltage-current deviation on production process. Thus the unbalancing of each LED strings current occurred by its characteristic deviation. This unbalancing reduce a uniformity of the flux of light. Therefore, we researched to design method the LED driver based on DSP and the balancing transformer for a LED current balancing. These are applied to 50W LED module consist of 4 parallel strings. We analyzed the reduction of LED currents unbalance by experimental result from each method.

• The Journal of the Korea Contents Association
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• v.21 no.12
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• pp.302-309
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• 2021

The section speed enforcement system measures the starting instantaneous speed, the The section speed enforcement system measures the starting instantaneous speed, the ending instantaneous speed, and the section average speed, and imposes fines only for the portion that has been speeding the most. However, according to the Road Traffic Act, most of the systems are installed on highways, so existing research has been conducted on highway sections. In this study, it is expected that the installation of section speed enforcement systems on general national roads will be expanded according to the revision of related laws. ITS collection and operation data targeting the section speed enforcement system installed on National Road 3 Seongnam Icheon-ro was used to analyze traffic speed, standard deviation of traffic speed, and reduction in traffic accidents by dividing it into before installation, trial operation period, and after crackdown. As a result of the analysis, the traffic speed, standard deviation, and traffic accidents decreased by 13%, 25%, and 70%, respectively, after installation, confirming that the installation of the section speed enforcement system greatly contributed to the reduction of accidents.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.4
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• pp.345-354
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• 2006

During installation of face bolts, they are often deviated from the designed horizontal direction. In this study, a laboratory test and numerical analysis were conducted to examine the change of support effect by them. Also, the number of bolts to be added for achieving the designed support effect was considered. It was verified in this study that the horizontal installation is more effective. Under the test condition of this study, 1.5 bolts/section should be added in the face of which the installation density was 3 bolts/section when the bolts were installed with $R15^{\circ}$ angle from the horizontal position.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.163-167
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• 2009

Although the domestic electric power consumption of lighting have shared 20${\sim}$30 % of the national electric power consumption, the spread of lighting control system which can reduce the electric power consumption have been insignificant. The government have set the demonstration project and given the incentive to promote the spread of lighting control system since 2008. The M&V (Measurement and Verification) methodology for lighting control system have not been set yet in our country, but the direct measurement was suggested in US. The direct measurement methodology can increase the accuracy of measurement, but it cost much money to burden a customer. This study have suggested a new M&V methodology which cost low and is simple relatively. I had measured the amount of electric consumption through both the direct measurement and the new M&V program computation, and have analyzed the deviation. The amount of electric consumption measured by the new M&V program computation have agreed with one by the direct measurement within the error range of the instrumentation in case of lab scale test, and the 4${\sim}$8 % deviation have existed in case of field evaluation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.12
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• pp.38-43
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• 2013

In this paper, the location measurement method for the reliable location data using ultrasonic sensors is proposed for the dimming control of the LED flat lamp. The measurement errors depending on the reflection angle of the object have to be considered to obtain the reliable location data in the ultrasonic sensors. In the experiment, the cause of the measurement errors depending on reflection angle is analyzed and velocity change of ultrasonic wave depending on reflection angle is measured. And the location measurement method depending on velocity change of ultrasonic wave is proposed. From the results, the average absolute deviation of the x-coordinates was 1.47cm when the location measurement method was considered, and it was closer to the true values than the average absolute deviation of the x-coordinates which was 5.89cm without regard to the reflection angle.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.10
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• pp.584-592
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• 2003

This paper presents a fuzzy-GA method for the allocation and operation of dispersed generator systems(DGs) based on load model in composite distribution systems. Groups of each individual load model consist of residential, industrial, commercial, official and agricultural load. The problem formulation considers an objective to reduce power loss of distribution systems and the constraints such as the number or total capacity of DGs and the deviation of the bus voltage. The main idea of solving fuzzy goal programming is to transform the original objective function and constraints into the equivalent multi-objectives functions with fuzzy sets to evaluate their imprecise nature for the criterion of power loss minimization, the number or total capacity of DGs and the bus voltage deviation, and then solve the problem using genetic algorithm. The method proposed is applied to IEEE 12 bus and 33 bus test systems to demonstrate its effectiveness. .

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.6
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• pp.416-426
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• 2008

The boiler tube failure often experienced in the superheater of a utility boiler can seriously affect the economic and safe operation of the power plant. It has been known that this failure is mainly caused by the thermal load deviation in the superheater tube system, and deeply intensified by the non-uniform distribution of steam flow rates. The nonuniform steam flow is distinctively prominent at low power load rather than at full power load. In this paper, we analyze the steam flow distribution in the superheater tube system by using one dimensional flow network model. At 30% power load, the deviation of steam flow rate is predicted to be within 0.8% of the averaged flow rate. This deviation can be reduced to 0.1% and 0.07% by assuming two cases, that is, the removal of 13th tube at each tube rows and the installation of intermediate header, respectively. The assumed two cases would be effective for the uniform steam flow distribution across 85 superheater tube rows.

• Journal of Bio-Environment Control
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• v.18 no.3
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• pp.215-224
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• 2009

A survey on the actual state of heating, cooling, ventilation, and air-flow and experimental measurement of temperature and humidity distribution in tomato greenhouse were performed to provide fundamental data required in the development of air-flow control technology. In single-span plastic houses, which account for most of 136 tomato greenhouses surveyed, roof windows, ventilation and air-flow fans were installed in a low rate, and installation specs of those facilities showed a very large deviation. There were no farms installed greenhouse cooling facilities. In the hot air heating system, which account for most of heating type, installation specs of hot air duct showed also a large deviation. The exhaust air temperature and wind speed in hot air duct also were measured to have a big difference depending on the distance from the heater. We are using the maximum difference as indicator to determine whether temperature distribution is uniform. However if the temperature slope is not identical in greenhouse, it can't represent the uniformity. We analyzed relation between the maximum difference and the uniformity of temperature and humidity distribution. The uniformity was calculated using the mean and standard deviation of data from 12 measuring points. They showed high correlation but were represented differently by linear in the daytime and quadratic in the nighttime. It could see that the uniformity of temperature and humidity distribution was much different according to greenhouse type and heating method. The installation guidelines for ventilation and air-flow fan, the spread of greenhouse cooling technology for year-round stable production, and improvement of air duct and heating system, etc. are needed.