• Korean Journal of Optics and Photonics
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• v.11 no.5
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• pp.353-359
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• 2000

A harmonically mode-locked fiber ring laser cavlty was theoretically analyzed. The measured charactenstlcs of a 10 GHz erbium-doped fiber ring laser were used as a basis of the theoretical analysis. From the nonlinear Schroedinger equation of an actively mode-locked erblUm-doped fiber laser. the effects of the components inside the laser cavity have been analyzed includmg nonlinear effects from group-velocity dispersion (GVD) and self-phase modulation (SPM). Usmg the analysls. we have designed a laser cavity with minimum pulsewidth and chirp by changing the intracavity optical intensity and the bandwidth of the filter. In the new design, the chirp i, reduced by 2 times and the pulsewidth by 2A times. compared to the laser used in the experiment. iment.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.5
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• pp.567-574
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• 2014

In this paper, a VHF antenna with monopole structure is designed and fabricated for marine wireless communication applications. The proposed antenna is based on a monopole design, and composed of circular ring and meander structure for VHF operation which cover VHF frequency bands. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and found the parameters that greatly effect antenna characteristics. Using the obtained parameters, the antenna is fabricated. The experiment results demonstrated that the proposed antenna satisfied the -10 dB impedance bandwidth requirement while covering the VHF bands. And measured characteristics of gain and radiation patterns are obtained for operating bands.

• Bulletin of the Korean Chemical Society
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• v.22 no.9
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• pp.984-988
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• 2001

Since anti-angiogenesis could lead to the suppression of tumor growth, angiogenesis inhibitors have received particular attention for their therapeutic potential. In this study, two angiogenic inhibitors using the bioactive sequence from the kring le 5, AK1(KLYDY), AK2(KLWDF) were designed and synthesized. We have investigated their solution structures using NMR spectroscopy and their activities as angiogenesis inhibitors. AK2 has an intramolecular hydrogen bon d between the side chain amino proton of Lys1 and the carboxyl oxygen of Asp4 with a N ${\cdot}{\cdot}{\cdot}$O distance of $3.27\AA$, while AK1 shows more flexible structures than AK2. Indole ring in Trp is much bigger than the phenyl ring in Tyr and may have good face-to-edge interaction enforcing more rigid and constrained conformational features of AK2. Because of this relatively stable structure, Trp3 in AK2 may have better hydrophobic interaction with Phe5 than Tyr3 in AK1 if two adjacent aromatic groups are located in hydrophobic pocket of receptor. Since AK2 shows the similar anti-angiogenic activities to AK1, we are also able to confirm that the activity of AK1 is irrelevant to the Tyr phosphorylation. More rigid drug with higher activities can be provided by the mimetic approaches. For the further development of the angiogenesis inhibitors, these conformational studies on our lead peptides will be helpful in design of peptidomimetics.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.48-54
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• 1995

A new propeller open water testing device is developed and tested in a tow tank. The devised dynamometer consists of a torque measuring part, a thrust measuring part and a driving motor with an RPM counter. Torque is designed to be measured directly from the torsion of the structure holding the motor by using strain gauges and, consequently, conventional slip ring is removed. Also, in order to make the device fit in relatively small model ships, the weight and the size of the whole integrated structure are reduced in various ways. The developed tester is proved to be easily utilized in small circulating water channel experiments and is believed to have provided us with essential information for future design of various types of conventional or object oriented force measuring device.

• Tribology and Lubricants
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• v.35 no.1
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• pp.71-76
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• 2019

The differential planetary gear reducer as a main component of the concrete mixer driving mechanism requires a strong torque to mix concrete compounds. As this component is currently dependent on imports, it is necessary to develop it by conducting a study on vibration analysis and the resonance problem. The noise and vibration of a concrete mixer reducer increase owing to the transmission error of planetary gears, and the damage of components occurs owing to the problems in design and production. In this study, the tooth-passing frequency is calculated to evaluate the noise and vibration of a mixer reducer, and a fast Fourier transform (FFT) analysis is conducted through a vibration test using an acceleration sensor. The vibration of the reducer is measured at three points of input and output of the shaft and planetary gear housing with fixed and variable revolutions per minute. The operating conditions of gears and bearings are evaluated by performing the FFT analysis, and the resonance problem is verified. The results show that No. 1 pinion and ring gears revolve disproportionately. The amplitude values appear high, and the wear of tooth faces occur in tooth-passing frequencies and harmonic components of No. 1 and No. 2 pinion-ring gears. Therefore, we conclude that design changes in the reducer and a correction of tooth profiles are required.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1468-1475
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• 2023

Enhancement of wear resistance of components used in fast reactors is necessary for long service life of the components. Plasma nitriding is a promising surface modification technology to impart high hardness and improved wear resistance of various steel components. This study discusses the characterization of chrome nitrided SS316L casing ring used in secondary sodium pump of fast breeder reactor and its stability under long term sodium exposure. Microstructural and hardness analysis showed that stress relieved component could be chrome nitrided successfully to a thickness of about 100 ㎛. Assessment of in-sodium performance of the chrome nitrided casing ring subjected to long term exposure up to 5000h at 550℃, showed retention of chrome nitrided layer with a case depth almost similar to that before sodium exposure. A slight decrease in the hardness was observed due to prolonged high temperature sodium exposure. Tribological studies indicate very low coefficient of friction indicating the retention of good wear resistance of the coating even after long term sodium exposure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.4
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• pp.271-274
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• 2013

Power Metal Oxide Semiconductor Field Effect Transistor's (MOSFETs) are well known for superior switching speed, and they require very little gate drive power because of the insulated gate. In these respects, power MOSFETs approach the characteristics of an "ideal switch". The main drawback is on-resistance RDS(on) and its strong positive temperature coefficient. While this process has been driven by market place competition with operating parameters determined by products, manufacturing technology innovations that have not necessarily followed such a consistent path have enabled it. This treatise briefly examines metal oxide semiconductor (MOS) device characteristics and elucidates important future issues which semiconductor technologists face as they attempt to continue the rate of progress to the identified terminus of the technology shrink path in about 2020. We could find at the electrical property as variation p base dose. Ultimately, its ON state voltage drop was enhanced also shrink chip size. To obtain an optimized parameter and design, we have simulated over 500 V Field ring using 8 Field rings. Field ring width was $3{\mu}m$ and P base dose was $1e15cm^2$. Also the numerical multiple $2.52cm^2$ was obtained which indicates the doping limit of the original device. We have simulated diffusion condition was split from $1,150^{\circ}C$ to $1,200^{\circ}C$. And then $1,150^{\circ}C$ diffusion time was best condition for break down voltage.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.225-235
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• 2013

Cutter forces acting on a disc cutter in TBM are the key parameters for TBM design and its performance prediction. This study aimed to experimentally evaluate cutter forces with different ring shapes in a hard rock. The stiffness of a cutter ring was indirectly estimated from a series of full-scale linear cutting tests. From the experiments, it was verified that the rolling stress acting on a V-shape disc cutter was much higher than on a CCS disc cutter even though the penetration depth by a V-shape disc cutter could be increased in the same cutting condition. Finally, it is suggested that a prediction model considering the shape parameters of a disc cutter should be used for its better prediction.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.9
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• pp.79-84
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• 2008

Switching speeds increase in both frequency and the transition rate of edges. Inadequate forecast for simultaneous switching signals may cause designing the power planes without sufficient current capability. The delay of critical signals in a chip can be therefore inadvertently increased and the situation makes it hard to debug issues. It is important to find the degree of increased switching during the debugging or chip characterization phases. This paper proposes the interpolation method to predict the switching density in a design. The interpolation was achieved by utilizing the dependencies between switching frequency and the delay appeared in a ring oscillator. The ring oscillator was primarily used to accumulate the effects of the ground bounce by higher switching. The result of interpolation was demonstrated using DongBu Hitec 0.18um CMOS technology.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.85-91
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• 2003

Intracavity frequency doubling of a single-mode Nd:YAG laser by using a nonplanar ring cavity is demonstrated. The nonplanar ring cavity consists of a Brewster-angled Nd:YAG crystal placed in a magnetic field, a KTP crystal, and two spherical mirrors. In this design the Nd:YAG block acts as both a nonreciprocal polarization rotator and a partial polarizer, and the nonplanar portion of the ring cavity, which is formed by a relative twist angle between the Brewster-angled end surfaces of the Nd:YAG block, serves as a reciprocal polarization rotator. An eigenpolarization theory for the cavity configuration is presented and suitable values of the relative twist angle for unidirectional operation are estimated. A single-mode output power of 22 ㎽ at 532 nm and an optical to optical conversion efficiency of 1.8% are obtained with a 1.2 W diode laser at 809 nm.