• Journal of Welding and Joining
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• v.21 no.6
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• pp.20-25
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• 2003

Various welding methods such as Gas Tungsten Arc Welding(GTAW), magnetic force electrical resistance welding and Laser Beam Welding(LBW) are now available for end cap closure of nuclear fuel rods. Even though the resistance and GTA welding processes are widely used in manufacturing commercial fuel rods, they can not be recommended for the remote seal welding of fuel rods in the hot cell Facility due to the complexity of the electrode alignment, the difficulty in replacing parts in a remote manner and the large heat input for the thin sheath. Therefore, the Nd:YAG laser system using optical fiber transmission was selected for the end cap welding of irradiation fuel rods in the hot cell. The remote laser welding apparatus in the hot cell Facility was developed using a pulsed Nd:YAG laser of 500 watt average power with an optical fiber transmission. The weldment quality such as microstructure and mechanical strength was satisfactory. The optimum conditions of laser welding for encapsulating irradiation fuel rods in the hot cell were obtained.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.4
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• pp.95-103
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• 2012

In this paper, we implemented a surveillance system for the power transmission line protection from heavy-duty fender-bender. Laser scanning technology was applied for system design. It was analyzed detailed functions for designed system. Measured detection rate and error rate that are monitoring parameters for both studied system and conventional system were 100%, 0% and 95.8%, 2.1%, respectively. Measurement showed that studied system is almost perfect and better than conventional system. Because this system provides the information to frontline workers with managers of heavy equipments that have possibility of accident, it can be applied to surveillance system for the transmission line protection.

• Korean Journal of Optics and Photonics
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• v.15 no.3
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• pp.263-267
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• 2004

We have investigated the characteristics of a Nd:YAG laser pumped by a cw Ti:sapphire laser. When the pumping power of the Ti:sapphire laser was 850 ㎽, the maximum output power of the Nd:YAG laser was 450 ㎽. As a result, the slope efficiency for the output power of the Nd:YAG laser was measured to be 56%. We have also investigated the characteristics of a passively Q-switched Nd:YAG laser by using a Cr$^{4+}$:YAG as saturable absorber with initial transmission of 90%. The maximum average output power of 200 ㎽ was obtained with repetition rate of 23.8 KHz and pulse width of 17.0 ns.

• Journal of the Optical Society of Korea
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• v.12 no.1
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• pp.31-37
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• 2008

To increase output power of a He-Ne laser we propose to use the capacitive rf discharge and implement four channel structure. Most of experiments were carried out with a single laser tube from this structure to optimize the output mirror transmission, pressure and composition of the mixture. A laser tube of 2.8 mm inner diameter and 50 cm discharge length can give an output power of above 5.5 mW at 3.39 ${\mu}m$. Four such tubes in "matrix" structure let us obtain 20 mW of output. Simplified models which can be used to evaluate the behavior of an equivalent electrical circuit with laser plasma and qualitative characteristics of output power of He-Ne laser were also described.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.275-277
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• 1993

It is practically required to develop an optical transmission system, for the diagnosis of electric power apparatus, which enables to distinguish the right signals related to the partial discharge taken place inside the apparatus. These partial discharges are transformed into ultra sonic signals by the sensor and then used for the voltage application to pokels cell. Afterwards, the modulated laser beam is transmitted through the optical fiber. Throughout this work, a laser-beam based detecting system is developed and permits us to reproduce the transmitted signals indirectly without electromagnetic interference. For this purpose the characteristics of this system is well analyzed by means of different type of signals from function generator.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.969-975
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• 2009

In this paper, bonded wafer analysis system is proposed using laser beam transmission; while the transmission model is derived by simulation. Since the failure of bonded wafer stems in void existence, transmittance deviations caused by the thickness of the void are analyzed and variations of the intensity through the void or defect easily have been recognized then the testing power has been increased. In addition, large screen display on laser study has been done which resulted in acquiring a feasible technique for analysis of the whole bonding surface. In this regard, three approaches are demonstrated in which Halogen lamp, IR lamp and laser have been tested and subsequently by results comparison the optimized technique using laser has been derived.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.749-765
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• 2010

There are on-going efforts to utilize guided waves for structural damage detection. Active sensing devices such as lead zirconate titanate (PZT) have been widely used for guided wave generation and sensing. In addition, there has been increasing interest in adopting wireless sensing to structural health monitoring (SHM) applications. One of major challenges in wireless SHM is to secure power necessary to operate the wireless sensors. However, because active sensing devices demand relatively high electric power compared to conventional passive sensors such as accelerometers and strain gauges, existing battery technologies may not be suitable for long-term operation of the active sensing devices. To tackle this problem, a new wireless power transmission paradigm has been developed in this study. The proposed technique wirelessly transmits power necessary for PZT-based guided wave generation using laser and optoelectronic devices. First, a desired waveform is generated and the intensity of the laser source is modulated accordingly using an electro-optic modulator (EOM). Next, the modulated laser is wirelessly transmitted to a photodiode connected to a PZT. Then, the photodiode converts the transmitted light into an electric signal and excites the PZT to generate guided waves on the structure where the PZT is attached to. Finally, the corresponding response from the sensing PZT is measured. The feasibility of the proposed method for wireless guided wave generation has been experimentally demonstrated.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.2
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• pp.26-38
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• 1994

We demonstrate a repeatless transmission of 2.5 Gbps digital signal over 98 km opticla filbers using optical transmitter and optcial receiver which are designed and implemented using commercially available devices. The optical transmitter is realized by using a distributed feedback(DFB) laser. Temperature of the laser is thermoelectrically stabilized and the output optical power is also stabilized by using negative feedback. The output power of the transmitter is 0 dBm. The optical receiver consists of an InGaAs avalanche photodiode, a preamplifier. an automatic gain control amplifier, and a clock/data regenerator. We find an optimum decision threshold that gives the best receiver sensitivity form the measured V curve. The best sensitivity is -35.5dBm( BER-1*10S010T, PRBS=2S023T -1 ) and the overload power is -9 dBm. Finally, we achieve error free optical transmission with 98 km optical fibers. The exinction ration penalty of 2 dB. the chromatic dispersion penalty of 1 dB, and the total power penalty of 3.0 dB are measured. These results satisfy CCITT recommendation.

• Korean Journal of Optics and Photonics
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• v.7 no.1
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• pp.28-36
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• 1996

We have constructed and studied a laser system which consists of a multiplex spark gap with 8 couples of spark gaps and a multiple parallel plate capacitor type Blumlein transmission line circuit. In this laser system, the length of the laser tube, the length of the multiplex spark gap and the total thickness of the transmission line circuit are chosen to be 520 mm. The experimental results show that one couple of spark gaps cannot give a uniform and complete lasing through the whole laser tube. All the more, a multiplex spark gap could not perform completely and synchronously. However, a multiplex spark gap in found to contribute to the increase of laser output power and the laser has performed the best when the location is three quarters of the laser tube length.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.2
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• pp.289-293
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• 1996

The basic study on laser triggered lightning was carried out for the active protection of lightning in power transmission system. The lengths of generated plasma channels were simulated numerically for variations of energy and pulse width of CO$_{2}$ laser by Runge-Kutta-Gill method. As results, the effective lengths of plasma channels were 2.3m, 2.67m and 3.4m respectively for energy of 45J, 60J and 100J of CO$_{2}$ laser pulse with pulse width of 50nsec using focusing mirror with focal length of 10m. And also the effects of pulse width of first pulse and tail pulse of CO$_{2}$ laser on the length of plasma channel were examined.