• The Journal of Korean Institute of Information Technology
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• v.17 no.3
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• pp.43-50
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• 2019

In this paper, we propose a S-band oscillator with a reduced electrical size by applying a vertical split ring resonator(VSRR). The VSRR is a type of split ring resonator that operates as a resonator by the capacitance and inductance generated between the microstrip lines arranged on the top and bottom of the dielectric substrate and it has an advantage that the electrical size of the resonance circuit can be reduced as compared with the conventional ring resonator. In this paper, we design a VSRR operating over S-band and an oscillator using the VSRR as the resonant circuit. The proposed oscillator showed the output of 5.9dBm at 2.4HGz and showed the phase noise characteristics of -112.58dBc at 100KHz offset frequency and -117.85dBc at 1MHz offset.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.9
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• pp.25-32
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• 2006

In this study, the characteristics of filament wound composite/aluminum ring specimens were investigated at cryogenic temperature. The ring specimens were manufactured using carbon fibre and Type B epoxy resin which had been developed for cryogenic use. As a result of measuring thermal strains at -150℃, it was found that compressive thermal stress was induced in composite part on the contrary, tensile thermal stress in aluminum part which was about 32% of yield stress and in turn, caused aluminum to be yielded at lower load level. In addition, Thermal strains which resulted from finite element analysis showed good agreement with those of the experiment. After 6 mechanical loading cycles had been applied to the ring specimen at -150℃, tensile tests were performed at -150℃ using a split disk fixture. As a result, it was shown that composite strength in a liner-composite tank structure which is for the use of cryogenic propellant tank would be decreased by auto-frettage pressure which is applied to it.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.4
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• pp.512-519
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• 2012

This paper proposes a 3-D pose (positions and orientations) estimation system based on the recognition of circular ring patterns. To deal with monocular vision-based pose estimation problem, we specially design a circular ring pattern that has a simplicity merit in view of object recognition. A pose estimation procedure is described in detail, which utilizes the geometric transformation of a circular ring pattern in 2-D perspective projection space. The proposed method is evaluated through the analysis of accuracy and precision with respect to 3-D pose estimation of a quadrotor-type vehicle in 3-D space.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.7
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• pp.1538-1543
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• 2013

In this paper, a novel split ring resonator is proposed for improvement of phase noise characteristics that is weak point of oscillator using planar type microstrip line resonator. Oscillator using proposed split ring resonator is designed, it has improved phase noise characteristics. At the fundamental frequency of 5.8GHz, 7.22dBm output power and -83.5 dBc@100kHz phase noise have been measured for oscillator with split ring resonator. The phase noise characteristics of oscillator is improved about 9.7dB compared to one using the general ${\lambda}/4$ microstrip resonator. Next, we designed voltage controlled oscillator using proposed split ring resonator with varactor diode. The VCO has 125MHz tuning range from 5.833GHz to 5.845GHz, and phase noise characteristic is -118~-115.5 dBc/Hz@100KHz. Due to its simple fabrication process and planar type, it is expected that the technique in this paper can be widely used for low phase noise oscillators for both MIC and MMIC applications.

• Journal of Technologic Dentistry
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• v.19 no.1
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• pp.5-12
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• 1997

To examine the difference of castability of non -precious porcelain metal according to 2 type of investing method, experiments were carried out using the method of both existing investing method and the investment with spaces to the upper & lower parts of the ring. The following conclusion were obtained from the result. 1. Seperataly using the existing investment and with spaces to the upper & lower parts of the ring, 44 samples resulted in success with the former method and 52 with the latter out of 84 samples. 2. Under the existing investing method, 44 samples out of 56 total resulted in success when the temperature of the ring was $870^{\circ}C$, and all samples failed when the temperature was $800^{\circ}C$. 3. Under the investment that gives space to the ring, when casted with the temperature of the ring fixed at $870^{\circ}C$, 40 samples out of 56 and 17 samples with the temperature fixed at $800^{\circ}C$ resulted in success. 4. Under the existing investing method with the temperaure of the ring fixed at $870^{\circ}C$ and heat soaking time given an hour, 26 out of 28 samples resulted in success and 18 resulted the same with half an hour heat soaking time. 5. Using the investment that gives space to the ring, at ring temperature $870^{\circ}C$ with heat soaking time 1 hour, all of total 28 rusulted insuccess however only 12 smaples succeeded with 30 minutes heat soaking time. 6. Under the existing investing method, samples with heat soaking time 1 hour equally given at ring temperature $870^{\circ}C$, 26 samples out of 28 succeed however at $800^{\circ}C$ all samples failed. 7. In the case of ring's upper and lower parts opened ring temperature is $870^{\circ}C$ and $800^{\circ}C$ and the heat soaking time was fixed at 1 hour, all 28 samples resulted in success and at $800^{\circ}C$ 17 succeed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1125-1131
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• 2009

O-rings are commonly used in machines as a seal. Due to prolonged use the surface of an O-ring can degrade which can lead to leakage as well as contamination. Damage of O-rings used in vacuum applications such as sputter is caused by various mechanisms. Particles detached from the O-ring may cause significant problems on the performance of the system in the vacuum chamber. Therefore, understanding the tribological behavior of O-rings is important to tackle the damage caused by repeated contact. In this work, FKM rubber was used for friction and wear tests conducted to investigate the tribological behavior of O-rings. A reciprocating type of a tribo-tester was used for the tests. The friction coefficient between the steel ball and the FKM specimen was quite high. Also, in order to identify the wear behavior, the surface of the FKM specimen was characterized using both optical and scanning electron microscopes. Evidence of wear due to adhesion and extrusion could be found. The results of this work will aid in improving the durability of O-rings.

• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.288-295
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• 1995

We have studied about spatial wavefront analysis of a pulsed laser output beam by means of an imaging unstable ring resonator with an infinite Fresnel number. We have constructed a Newtonian telescope type NBUR (Negative Branch Unstable Ring) Nd:YAG laser with 4 plane mirrors. Provided that the NBUR resonator is under self imaging condition, the resonator could be reduced diffraction effects which were occuring to the beam transmitting through the circular aperture of scraper mirror in the resonator. We have observed enhancement in the spatial coherence of wavefronts of laser beam due to the iterative round trips of the self imaging beam inside the ring resonator. The information on the spatial wavefronts was determined by the fringe patterns from Mach-Zehnder interferometer and the fringe analysis by means of the Fourier transform method showed the distortion of wavefronts of less than 0.2), In comparison with a standing wave type resonator, we have confirmed that the spatial coherence of the NBUR Nd:YAG laser output beam was enhanced as much as 75%. s 75%.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.4
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• pp.38-45
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• 2017

A finite element analysis-based approach which investigates the causes of the breakdown in the outer ring of the choke at hot rod rolling mill is presented. Two-dimensional drawings of the whole vertical-type mill stand are transformed into three-dimensional CAD models. Non-linear elasto-plastic deformation analysis of material at the roll gap is performed for computing roll force and torque of the work roll. Then, the reaction forces of the bearing rings together with a set of roller bearings that support the work roll are obtained by means of rigid body motion analysis. Finally, stress behaviors in the bearing rings together with a set of roller bearings that support the work roll are investigated by linear elastic analysis. Results reveal that stress at the contact area between the outer ring and roller bearing is extraordinary high when an internal gap between an external surface of the outer ring and the internal surface of the chock due to wear of the inside of the chock occurs.

• The Journal of the Acoustical Society of Korea
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• v.32 no.6
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• pp.484-493
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• 2013

Typical underwater acoustic sensors can measure the scalar quantity of sound-pressure-magnitude with the limitation of being unable to identify the direction of an incoming wave. This paper proposes a method to detect the direction of the sound wave with a ring sensor. The sensor of the proposed structure has a piezoceramic ring divided into eight elements, and distinguishes the direction of the sound wave by properly combining the output voltages of the piezoceramic elements. Further, through the analysis of the effects of the structural parameters like the ring radius and length, and piezoceramic thickness, we have suggested the way to improve the sensitivity of the vector sensor.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.2
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• pp.268-275
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• 2008

The shape and array of ice capsules are very important factors in ice thermal storage system because the heat transfer rate of the system strongly depends upon them. In this paper, a new type of ice capsule composed of bar and ring module is proposed to increase the efficiency of the ice thermal storage system. To investigate the heat transfer rate of the proposed ice capsule, numerical analysis of the incompressible Navier-Stokes equations is performed to compare the proposed bar and ring system with the conventional ice capsules. It is shown that the ice capsule composed of bar and ring has a higher heat transfer rate and a low outlet temperature than the conventional ice capsules for various packing ratios and entrance velocities. Furthermore, it is found that the optimal entrance velocity exists between 0.005 m/s and 0.007 m/s from the present numerical analysis.