• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.265-271
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• 2003

This study is for the stable optical source in order to get the precision measurement, which contributes to help the laser frequency and the output to be settled. The laser optical frequency is changed by the length of resonance cavity. The length variation of the laser resonance amplitude is affected by the thermal expansion of that system. So, we try not only to adjust the temperature of the laser tube using the heater for fine length of resonance cavity, but also to maintain the fixed temperature of the resonance cavity for outputting the safe laser optical frequency. Therefore, we must take materials with the thermal expansion of the supporting system, which is closer to it of the laser resonance cavity. Using the materials, we can promote to stabilize the temperature of it. In advance, we also plan to get the settlement of the laser frequency and the output in the long km, optimizing and stabilizing the system.

• Elastomers and Composites
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• v.39 no.3
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• pp.179-185
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• 2004

Frequency dependency or electrical property stabilization during vulcanization of modified NR/IR composite materials was studied using in-situ electrical property measuring technique. Volume resistivity(p) before and after vulcanization reaction of the sample was measured as the function or frequency in the range or 1Hz to 10kHz at reaction temperatures of 130, 140, 150, and $160^{\circ}C$, respectively. A double stabilization mode of frequency dependency was observed, in which a slow stabilization process of p to a value of ca. $1.0{\times}10^7\;{\Omega}-cm$ occurred after a drastic initial decrease from ca. $9.0{\times}10^7\;{\Omega}-cm$. In addition, notable temperature dependencies of p values were also observed before and after vulcanization reaction, that is, p values at 130 and $140^{\circ}C$ after vulcanization were observed as about 1/3 of those values before vulcanization. All the observed facts were considered as the results from the interaction between the electrode and the bulk sample materials, i.e., electronic charge-discharge, and from the structure change of samples including CB rearrangement by the vulcanization.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.83-88
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• 2004

High voltage AC electric field has been applied to turbulent propane jets to investigate the effect of electric field on liftoff characteristics. Liftoff velocity and liftoff height have been measured by varying the applied voltage and frequency. Liftoff velocities were delayed and liftoff heights were reduced by applying AC, not by DC. The electric effect became disappeared with further increasing jet velocities, which shows that the effect can be explained by the balance between inertia force and electric force. The flame stabilization effect was intensified as either applied voltage or frequency increased. Plasma streamers were generated between the flame and the jet under high voltage conditions. Liftoff velocity in the absence of plasma can be well correlated by the function of voltage and frequency.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.33.2-33
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• 2001

The robust stability condition for sampled-data control systems with a sector nonlinearity was presented in our previous paper. Although it is applicable only to the sampled-data control system of a certain class, a usual discretetime control system can belongs to this type of class. This paper analyzes the amplitude dependent behavior of nonlinear sampled-data (i.e., discrete-time) control systems in a frequency domain. By considering restricted areas (sectors) in the nonlinear characterisitic, the existence of a sustained oscillation is estimated, and the relationship between the stable/unstable conditions and the result derived from describing function is compared. Based on these considerations, the stabilization of nonlinear discrete-time control systems is examined in the frequency domain.

• Journal of Communications and Networks
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• v.15 no.6
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• pp.569-575
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• 2013

In this paper, we present a photonic approach for generating highly stable coherent sub-terahertz (THz) signals for wireless communications. As proof-of-concept we transmit data at 100 GHz carrier frequency using on-off keying modulation and heterodyne detection. The sub-THz carrier signals are generated by photo-mixing two optical carrier signals at different frequencies, extracted from an optical frequency comb. We introduce a novel system to stabilize the phase of the optical carrier signals. Error-free transmission is successfully achieved up to a bit rate of 8.5 Gbit/s at 100 GHz.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.337-340
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• 2004

Stabilizing systems with Gyroscope are extensively used in various tracking devices for attaining the system's objective. Because of putting performance first in importance of system and focusing on specification of parts, designers are sometimes passing over the dynamic characteristics of system in vibrating condition. In this paper, we were dealing with unstable stabilizing control due to coincidence of stabilization platform natural frequency and that of Gyroscope used for sensing rate. For solving this problem, statics and dynamic test of silicon rubber with 3 different hardness were performed and similar stabilizing system was adopted to prove reasonability of rubber choice and static pre-strain.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.307-314
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• 2021

Even though the LCL filters have superior harmonic attenuation ability to L filters, stability has always been an issue. The system could be unstable because of the resonance phenomenon, especially when digital controller is used. Adding a notch filter to the compensator is one approach to solve the problem. Resonance phenomenon can be inhibited by aligning notch frequency to system resonance frequency. However, resonance frequency variation can be obtained because the actual system has a nonstationary characteristic. Therefore, the system could be unstable, where the system parameters are changed when the conventional notch filter is used. An adaptive digital notch filter that stabilizes the system even system parameters are changed. Simulation and experiment results are provided to verify the validity of the proposed adaptive filter.

• Journal of the Korea Institute of Military Science and Technology
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• v.26 no.1
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• pp.72-82
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• 2023

The EOTS(Electro Optical Tracking System) must have stabilization performance to provide high-quality images under disturbance environment. In this paper, we present a controller that can minimize the LOS error and has a simple structure. Hence, to evaluate the performance of this controller, analysis in the frequency domain and LOS error measurement are performed. In order to measure the LOS error without a 'rate table' that requires a lot of facility investment, we propose a design method for disturbance model that considers the operating environment of the EOTS. Finally, the performance of the stabilization algorithm is evaluated by the proposed disturbance model.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.859-865
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• 2010

We have designed and assembled a saturated absorption-spectroscopy system of $^{127}I_2$ for the frequency stabilization of the 543 nm He-Ne laser. The frequency of a internal-mirror 543 nm He-Ne laser was swept by utilizing the temperature and PZT change of the laser cavity length. Frequency modulation was applied to the output laser mirror with a PZT modulator for the third harmonic signal. A portion of the hyperfine spectrum originated from the R(12)26-0 and R(106)28-0 transitions of the B-X system of $^{127}I_2$ was observed as the third-derivative signal using a saturated absorption spectroscopy. The signal-to-noise ratio of a typical hyperfine spectrum signal was estimated to be 30:1.

• Advances in pediatric surgery
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• v.7 no.1
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• pp.21-25
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• 2001

Congenital diaphragmatic hernia (CDH) in the past was considered a surgical emergency requiring immediate operation. Several groups now advocate preoperative stabilization and delayed surgery. The treatment strategy for CDH in this institution is delayed surgery after preoperative stabilization. The aim of this study was to evaluate the results of delayed surgery. A retrospective review of 16 neonates with CDH was performed. Surfactant. conventional mechanical ventilation. high frequency oscillation. and nitric oxide were utilized for preoperative stabilization as necessary. The difference in outcome between two groups differentiated by the duration of the preoperative stabilization periods with mechanical ventilation (${\leq}$ 8 hours and > 8 hours) was determined. Chi-square test was used to analyze the data. There were 7 right-sided hernias and 9 left. The average duration of stabilization was 32.4 hours. Hepatic herniation through the defect was found in 6 cases and all died. The most common postoperative complication was pneumothorax. The mortality rate of the right side hernia was higher than the left (85.7% vs. 33.3%. p=0.036). Mortality rate of the group (N=8) whose preoperative stabilization period was 8 hours or less was better than that (N=6) whose preoperative stabilization period was more than 8 hours (25.0% vs. 83.3%. p=0.031). The overall mortality rate was 56.3%. The better prognosis was noticed in left side hernia. no liver herniation, or shorter preoperative stabilization period.