• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.263-266
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• 2007

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials since it can create an extremely high-pressure state in very short time. Two-stage light gas gun is being employed most extensively. The present experimental study has been conducted to develop a new type of ballistic range which can easily perform a projectile simulation. The experiment is conducted to find out the dependence of various parameters on the projectile velocity. The pressure in high-pressure tube, pressure of diaphragm rupture and projectile mass and piston mass are varied to obtain various projectile velocities. The flow field is visualized to see flow around projectile.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.2
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• pp.155-164
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• 2013

Two design techniques for more accurate and more convenient hybrid positioning system with visible light communication (VLC) and ad-hoc wireless network infrastructure are proposed, in order to overcome the problems of high estimation error, high cost, and limited service range of the conventional positioning techniques. First method is based on a non-carrier VLC based hybrid positioning technique for applications involving of low data rate optical sensing and narrow-range visible light reception from transmitter, and long-range positioning. The second method uses a 4 MHz carrier VLC-based hybrid positioning technique for a high data rate optical sensing and wide-range visible light receiving from transmitter, and mid-range positioning applications. In indoor environments with obstacles where there are long-range 7731.4cm and mid-range 2368cm distances between an observer and a target respectively, the hybrid positioning developed with two design techniques are tested, and the proposed system is verified and analyzed in this paper.

• Journal of Korea Multimedia Society
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• v.12 no.8
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• pp.1055-1065
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• 2009

High-dynamic-range (HDR) rendering technology changes the range from the broad dynamic range (up to 9 log units) of a luminance, in a real-world scene, to the 8-bit dynamic range which is the common output of a display's dynamic range. One of the techniques, iCAM06 has a superior capacity for making HDR images. iCAM06 is capable of making color appearance predictions of HDR images based on CIECAM02 and incorporating spatial process models in the human visual system (HVS) for contrast enhancement. However there are several problems in the iCAM06, including obscure user controllable factors to be decided. These factors have a serious effect on the output image but users get into difficulty in that they can't find an adequate solution on how to adjust. So a suggested model gives a quantitative formulation for user controllable factors of iCAM06 to find suitable values which corresponds with different viewing conditions, and improves subjective visuality of displayed images for varying illuminations.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.37-38
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• 2010

For MHz-class high frequency inverter in wireless power transfer applications, the voltage/current surges can be occurred in power stage when driving on the inverter. And also, the high-frequency oscillations can be produced at a high switching frequency due to the parasitic elements. The voltage and current stresses of the switching devices lead to the switching losses. The efficiency of the high frequency inverter will be reduced. And the inverter circuit with the sudden voltage and current fluctuations also generates the noise such as the EMI. Zero voltage, zero current switching technique can be used to reduce the switching loss and the noise. The high power density and high efficiency can be obtained. In this paper, the high-frequency inverter for short-range wireless power transfer applications was discussed. The feasible inverter circuit is analyzed in the circuit operating characteristics and the results are verified by the simulation.

• Journal of Power Electronics
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• v.7 no.2
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• pp.118-123
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• 2007

This paper presents a new ZCS-PWM high frequency inverter. Zero current switching operation is achieved in the whole load range by using a simple auxiliary reverse blocking switch in parallel with series resonant capacitor. Dual duty cycle control scheme is used to provide a wide range of high frequency AC output power regulation that is important in many high frequency inverter applications. It found that a complete soft switching operation can be achieved even for low power setting ranges by introducing high-frequency dual duty cycle control scheme. The proposed high frequency inverter is more suitable for consumer induction heating(IH) applications. The operation and control principle of the proposed high frequency inverter are described and verified through simulated results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.209-212
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• 2005

Recently, since structures have become extremely airtight with the development of high-rise apartments, mixed use residential and commercial buildings and offices, large capacity range hoods have become commonly implemented. However, the high noise level caused by this range hood system made of thin plate is the cause of increased complaints among users. In this study, the level of noise emitted from this type of range hood was measured by height at the user's location in the kitchen. It was confirmed that a great deal of noise was emitted in the downward direction of the hood. In order to minimize the noise emitted from this type of range hood, a new type of fan was manufactured. This was done by changing only the material and shape of the fan, since it was determined to be the primary source of noise emission. Then a comparison and evaluation were carried out regarding the noise characteristics between the new type of fan and the existing type of fan. As a result, it was confirmed that the noise from the new fan was reduced by more than 2 dB compared to the existing fan without noise interference at the discharge end.

• Journal of IKEEE
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• v.22 no.2
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• pp.309-315
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• 2018

A Stepped Frequency Radar(SFR) is a method of achieving high range resolution by gradually increasing the frequency of a transmitted pulse to create a wide synthetic bandwidth. However, in the case of moving target, accurate range estimation can not be performed due to the range-Doppler coupling phenomenon, so it is necessary to compensate through accurate velocity estimation. In this paper, we propose a stepped frequency radar waveform with a Coherent Pulse Train(CPT), velocity estimation results according to parameters using this method and VMD(Velocity Measurement Data) were compared and analyzed by numerical simulations.

• Journal of Environmental Health Sciences
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• v.5 no.1
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• pp.61-65
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• 1978

To investigate the phytoplankton distribution effected by polluted water, this research was carried out at eight sampling places in Tae-jun and one sampling place in Kang-kyong during the period from May 10 to July 25, 1977. The results are as follows. 1) The range of water temperature was 21.0~36.0$\circ$C (May 10~July 25), and pH value was in the range of 3.5~11.0. 2) BOD was generally high (140~432mg/l) 3) At the places where BOD was high, dominant species were Aphanocapsa rivularis, Microcystis aeruginosa and Oscillatoria sp. belonging to Cyanophyta, Chlorella sp. belonging to Chlorophyta, Euglena sp. belonging to Euglenophyta, and Navicula exqua and Navicula sp. belonging to Chrysophyta. 4) At the places where the range of pH value was 3.5~3.8 and the range of BOD value was 134~148mg/l, observable species were Scenedesmus ellipsoideus and Pandorina morurn belonging to Chlorophyta, Navicula exqua belonging to Chrysophyta and Euglena sp. belonging to Euglenophyta. 5) At the places where the range of pH value was 9.0~11.0 and the range of BOD value was 214~220mg/l, a few observable species were Scenedesmus carinatus, Scenedesmus ellipsoideus, Scenedesmus bijuga and Scenedesmus obundance belonging to Chlorophyta.

• The Journal of Korea Robotics Society
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• v.9 no.1
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• pp.28-38
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• 2014

This paper verifies the performance of Extended Kalman Filter(EKF) and MCL(Monte Carlo Localization) approach to localization of an underwater vehicle through experiments. Especially, the experiments use acoustic range sensor whose measurement accuracy and uncertainty is not yet proved. Along with localization, the experiment also discloses the uncertainty features of the range measurement such as bias and variance. The proposed localization method rejects outlier range data and the experiment shows that outlier rejection improves localization performance. It is as expected that the proposed method doesn't yield as precise location as those methods which use high priced DVL(Doppler Velocity Log), IMU(Inertial Measurement Unit), and high accuracy range sensors. However, it is noticeable that the proposed method can achieve the accuracy which is affordable for correction of accumulated dead reckoning error, even though it uses only range data of low reliability and accuracy.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.38 no.3
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• pp.31-39
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• 2001

In this paper, we proposed a new pixel circuit of the CMOS image sensor for high dynamic range operation, which is based on a multiple sampling scheme and a conditional reset circuit. To expand the pixel dynamic range, the output is multiple-sampled in the integration time. In each sampling, the pixel output is compared with a reference voltage, and the result of comparison may activate the conditional reset circuit. The times of conditional reset, N, during the integration will contribute to the increase of the dynamic range by the times of N. The test chip was fabricated with 0.65-${\mu}m$ CMOS technology (2-P, 2-M).