• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.73-76
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• 2006

Acoustic cavity as a stabilization device to control high-frequency combustion instabilities in liquid rocket engine is adopted and its damping capacity is verified in atmospheric temperature. Geometric effects of acoustic cavity on damping characteristics are analyzed and compared quantitatively. Satisfactory agreements have been achieved with linear acoustic analysis and experimental approach. Results show that the acoustic cavity of the largest orifice area or the shortest orifice length was the most effective in acoustic damping of the harmful resonant frequency finally, it is proved that an optimal design process is indispensable for the effective control of combustion instabilities.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.11
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• pp.2981-2994
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• 1995

In order to elucidate the effects of positive pressure gradient on flame properties, structure and stabilization, an experimental study is made on turbulent diffusion flame stabilized by a circular cylinder in a divergent duct flow. A commercial grade gaseous propane is injected from two slits on the rod as fuel. In this paper, stabilization, characteristics and flame structure are examined by varying the divergent angle of duct. Temperature, ion current and Schlieren photographs were measured. It is found that critical divergent angle is expected to be about 8 ~ 12 degree through blow-off velocity pattern to divergent angle and the positive pressure gradient influences the flame temperature, intensity of ion current and eddy structure behind the rod. With the increase of divergent angle, typical temperature of recirculation zone is low but intensity of ion current is high in shear layer behind rod. Energy distributions of fluctuating temperature and ion current signals turn up low frequency corresponding to large scale eddies but high frequency corresponding to small scale eddies as well as low with the increase of divergent angle. Therefore the flame structure becomes a typical distributed-reacting flame.

• Smart Structures and Systems
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• v.24 no.4
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• pp.459-474
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• 2019

This study develops a novel recursive algorithm to significantly enhance the computation efficiency of a recently proposed stochastic subspace identification (SSI) methodology based on an alternative stabilization diagram. Exemplified by the measurements taken from the two investigated office buildings, it is first demonstrated that merely one sixth of computation time and one fifth of computer memory are required with the new recursive algorithm. Such a progress would enable the realization of on-line and almost real-time monitoring for these two steel framed structures. This recursive SSI algorithm is further applied to analyze 20 months of monitoring data and comprehensively assess the environmental effects. It is certified that the root-mean-square (RMS) response can be utilized as an excellent index to represent most of the environmental effects and its variation strongly correlates with that of the modal frequency. More detailed examination by comparing the monthly correlation coefficient discloses that larger variations in modal frequency induced by greater RMS responses would typically lead to a higher correlation.

• Current Optics and Photonics
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• v.3 no.1
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• pp.33-39
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• 2019

We report development of a frequency-stabilized mid-infrared continuous-wave (cw) optical parametric oscillator (OPO) based on a fan-out grating MgO:PPLN crystal pumped at 1064 nm. The OPO resonator was designed as a pump-enhanced standing-wave cavity that resonates to the pump and signal beams. To realize stable operation of the OPO, we applied a modified Pound-Drever-Hall technique, which is a well-known method for powerful laser frequency stabilization. Tuning a poling period of the fan-out grating of the crystal allows wavelength-tunable OPO outputs from 1510 nm to 1852 nm and from 2500 nm to 3600 nm for signal and idler beams, respectively. At the idler wavelengths of 2500 nm, 3000 nm and 3500 nm, we achieved more than 50 mW of output powers at a pumping power of 1.1 W. The long-term stability of the OPO was confirmed by recording the power and wavelength variations of the idler for an hour.

• Fashion & Textile Research Journal
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• v.7 no.2
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• pp.225-230
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• 2005

This research was undertaken to compare basic bodice prototypes for Internet shopping customer, and to select a profitable fit vacant space quantity between clothing and body. A total one hundred of eighteen outfits (4 types of pattern ${\times}$ 9 subjects ${\times}$5 body areas) were constructed with basic bodice drafting method of Japan Bunka Women's University according to nine male body types. Fifty-two experts analysis of the different prototypes as five body area and evaluate the most appropriate ease amount and stabilization of the simulation images on the computer. The experiments with automated methods using simulation image are based on AZ program of TORAY, Japan. Data was analyzed using percentiles, frequency and $X^2$. Taken together, the present result of vacant space quantity and stability evaluation through images shows that there is a significant difference in the size variation of the chest circumference, shoulder slope and waist circumference. In case of ease amount, chest area, shoulder slope, waist area and armhole except neckline area were shown more appropriate on the basic bodice pattern without size change. In case of stabilization, the chest area, shoulder slope and armhole except waist area and neckline area was shown the best on the basic bodice pattern without size change. However the waist area was shown on the basic bodice pattern plus 2 cm, neckline was shown more appropriate on the basic bodice pattern plus 1cm.

• Journal of Korea Multimedia Society
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• v.20 no.8
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• pp.1236-1247
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• 2017

In this paper, we propose a method for evaluating the uncomfortable shaking in the video. When you shoot a video using a handheld device, such as a smartphone, most of the video contains unwanted shake. Most of these fluctuations are caused by hand tremors that occurred during shooting, and many methods for correcting them automatically have been proposed. It is necessary to evaluate the shake correction performance in order to compare the proposed shake correction methods. However, since there is no standardized performance evaluation method, a correction performance evaluation method is proposed for each shake correction method. Therefore, it is difficult to make objective comparison of shake correction method. In this paper, we propose a method for objectively evaluating video shake. Automatically analyze the video to find out how much tremors are included in the video and how much the tremors are concentrated at a specific time. In order to measure the shaking index, we proposed jitter modeling. We applied the algorithm implemented by Optical Flow to the real video to automatically measure shaking frequency. Finally, we analyzed how the shaking indices appeared after applying three different image stabilization methods to nine sample videos.

• Journal of Oral Medicine and Pain
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• v.13 no.1
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• pp.5-12
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• 1988

The purpose of this study was to evaluate the therapeutic effect of occlusal stabilization splint on the clinical symptoms and the condylar movement in patients with Temporomandibular Disorders(TMD). For the study, 15 TMD patients treated with stabilization splint and followed up were selected. The age of them was from 18 to 65 years and the mean period of treatment was 2.9 months. The author examined signs and symptoms of TMD according to Dr. Friction's evaluation from and recorded the condylar paths with Denar pantronic before and after splint therapy. The obtained results were as follows : 1. On the first visit, 11 patients(73.3%) showed muscle tenderness on palpation and the frequency was lateral pterygoid, masseter, medial pterygoid, temporalis, sternocleidomastoideus in the order named. 2. Occlusal stabilization splint was more effective in pain relief(100%) than in other dysfunction improvement(85.7%) 3. The amount of maximum opening increased from 37.1㎜ to 42.2㎜, but those of protrusion and laterotrusion changed little. 4. Pan. PRI scores decreased from 32.9 to 21.8, which meant improved reproducibility of mandibular border movements, and the group with sever dysfunction category showed more decrease in score than the group with moderate or slight dysfunction category.

• Journal of the Korean Society of Safety
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• v.23 no.4
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• pp.42-46
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• 2008

Ionizers are essential in various areas of manufacturing industries to protect electrostatic hazards and to reduce inferior products. For ion sources used in the charge neutralizers, there are corona discharge, soft X-ray, ultraviolet and glow discharge. Glow discharge has lots of attractive properties, such as lower discharge sustaining voltage, no generation of ozone, and so on. In this paper, we did an experimental study to trace the mechanism and stabilization of atmospheric pressure glow discharge using the several size and shape of electrodes. As an experimental result, to sustain conditions of atmospheric pressure glow discharge is that discharge voltage is 360V, discharge current is 12mA, apply frequency is 1kHz between electrodes when positive electrode is molybdenum(Mo) and negative electrode is copper(Cu). We confirmed that the mechanism and stabilization of atmospheric glow discharge is deeply concerned with the shape and material of electrode for discharge. Especially, glow discharge in atmospheric pressure was well generated and sustained according with the physical properties used electrode materials, example melting point, thermal conductivity, and etc.

• Journal of the Institute of Convergence Signal Processing
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• v.13 no.2
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• pp.77-82
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• 2012

This paper presents a hardware-implemented face regions stabilization algorithm that stabilizes facial regions using the locations and sizes of human faces found by a face detection system. Face detection algorithms extract facial features or patterns determining the presence of a face from a video source and detect faces via a classifier trained on example faces. But face detection results has big variations in the detected locations and sizes of faces by slight shaking. To address this problem, the high frequency reduce filter that reduces variations in the detected face regions by taking into account the face range information between the current and previous video frames are implemented in addition to center distance comparison and zooming operations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.5
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• pp.438-445
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• 2007

A Helmholtz resonator as a stabilization device to control high-frequency combustion instabilities in liquid rocket engine is adopted and its damping capacity is verified by linear acoustic analysis and atmospheric acoustic tests. To compare the results of acoustic attenuation effect in accordance with uni-resonator's geometry, quantitative analyses were made in the cases of various orifice diameters and lengths. Next, in the experiments to compare the results of acoustic attenuation effect by a difference in the number of resonators, damping capacity of harmful resonant frequency was improved by the increase of the number of resonators. On the other hand, attenuation efficiency of the frequency tended rather to lower due to over damping from the point of view of absorption coefficient. As the result, tuning the suitable geometry for the resonator to the resonant frequency is required for the control using the resonator. Also, the design of resonator's geometry and the choice of its number are important to put up the optimal efficiency in consideration of restriction of its volume.