• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7C
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• pp.743-754
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• 2006

In the proposed method, two regular laser working at two different wavelengths perform moving object detection alternatively in time. The laser intensity and the beaming period of each laser is equally maintain as to the single laser radar, hence, externally, dual beam lasers radar works exactly same as the single beam laser radar except that the proposed dual lasers radar needs additional post-processing of received signals in the receiver. To verify the robustness of the proposed method, a set of computer simulation has been performed. The communication channel is assumed to be additive white Gaussian noise, and the perfect synchronization is assumed. All other simulation parameters such as signal power and signalling period are equally maintain in both systems while the signal processing time such as spreading and filtering are expected to be trivial in call cases.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1110-1116
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• 2004

Experimental measurements of laser-induced ion mobility(LIIM) were performed for ethene/air premixed flames operated near the soot inception point. Soot was ionized using a pulsed laser operated at 532 nm. The ionization signal was collected with a tungsten electrode located in the post-flame region. ionization signals were collected using both a single electrode and dual electrode configuration. Prior LIIM studies have focused on the use of a single biased electrode to generate the electric field, with the burner head serving as the path to ground. In many practical combustion systems, a path to ground is not readily available. To apply the LIIM diagnostic to these geometries, a dual electrode geometry must be employed. The influence of electrode configuration, flame equivalence ratio, and flame height on ionization signal detection was determined. The efficacy of the LIIM diagnostic to detect soot inception in the post-flame region of a premixed flame using a dual electrode configuration was investigated. For the different dual electrode configurations tested, the dual parallel electrode geometry was observed to be most sensitive to detect the soot inception point in a premixed flame.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.1-7
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• 2021

A computer simulation was performed to study the effectiveness of temperature on the type of laser heat source in the context of the heterogeneous welding of aluminum and copper materials. Three different types of heat sources were used in the computer simulation: 1) Single Beam Straight Scan, 2) Single Beam Wobble Scan, and 3) Dual Beam Straight Scan. Among these sources, dual beam straight scan was found to be the most effective from the viewpoint of heat source control. Because the difference between the melting temperatures of copper and aluminum is approximately 400℃, a clear separation of heating temperature was required, and the dual beam straight scan provided superior controllability in this regard. When using the dual beam, the temperature of the 90:10 split was considerably easier to control than that of the 50:50 split. The optimal offset was calculated to be 4 mm off to the copper side, where the melting temperature and thermal conductivity were higher. In this manner, computer simulation was effectively used for determining the optimal laser beam hear source control without performing an actual laser welding experiment.

• Structural Engineering and Mechanics
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• v.75 no.2
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• pp.133-144
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• 2020

This investigation is to study the effect of gravitational field and diffusion on a microstretch thermoelastic medium heating by a non-Gaussian laser beam. The problem was studied in the context of the dual-phase-lag model. The normal mode analysis is used to solve the problem to obtain the exact expressions for the non-dimensional displacement components, the micro-rotation, the stresses, and the temperature distribution. The effect of time parameter, heat flux parameter and gravity response of three theories of thermoelasticity i.e. dual-phase-lag model (DPL), Lord and Shulman theory (L-S) and coupled theory (CT) on these quantities have been depicted graphically for a particular model.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.1
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• pp.153-158
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• 2009

Stable and tunable dual-wavelength erbium-doped fiber ring laser(EDFL) using a single fiber Bragg grating(FBG) and two coil heaters is proposed and demonstrated. Installing two identical coils into a single FBG, the FBG is symmetrically divided into two different portions. While a current supply to the coil, the refractive index of the FBG under the coil is changed. The FBG can operate as a joint of two different FBGs. Due to the thermo-optic effect of a fiber, the resonance wavelength split into two peaks. The spacing between two adjacent channels was changed as much as the difference of heating power. It was tuned up to 3 nm of wavelength under the electrical power with a 1000 mW. Moreover, the lasing wavelength can be individually tuned without influencing to the adjacent channel.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.3
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• pp.654-659
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• 2011

We propose a novel method to reduce laser chirp and improve modulation performance in semiconductor laser by using dual-electrode structure. Dual-electrode structure is realized by segmenting a electrode on top of gain medium, as was the case of edge emitting laser diode, into electrically isolated two electrodes. By using the proposed structure, we have experimentally achieved a reduction of laser spectral width of 0.23 nm and an improvement of 2.5-dB receiver sensitivity at an 80-km fiber transmission for 10-Gbps NRZ (non-return-to zero) data stream.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.53-55
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• 2001

A dual probe laser Doppler vibrometer (LDV) that has one laser source and provides two independent object beams has been developed for the first time. An electronic circuit that converts light signal to electronic signal has been also developed using phase locked loop(PLL). It was found that this types of dual probe LDV can be used in differential mode and self-vibration compensation mode.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1838-1840
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• 2001

A dual probe laser Doppler vibrometer (LDV) that has one laser source and provides two independent object beams has been developed for the first time. An electronic circuit that converts light signal to electronic signal has been also developed using digital phase locked loop(DPLL). It was found that this types of dual probe LDV can be used in differential mode and self-vibration compensation mode.

• Medical Lasers
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• v.9 no.2
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• pp.110-118
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• 2020

The non-ablative fractional dual laser is equipped with two types of lasers, 1550 nm and 1927 nm in one device, and was approved by the United States Food and Drug Administration in 2013. The advantages of the non-ablative fractional laser (NAFL) include fewer side effects such as erythema, edema, post-laser pigmentation, and scab formation. Thus, the NAFL is preferred by both practitioners and consumers because it is convenient and safe for use. The 1550 nm erbium glass and 1927 nm thulium lasers are representative NAFLs that have been developed separately and are often used as a single-wavelength laser with proven clinical efficacy in various indications. The 1550 nm wavelength laser penetrates the dermis layer and the 1927 nm wavelength laser is effective for epidermal lesions. Therefore, targeting the skin layer can be easily achieved with both the 1550 and 1927 nm lasers, respectively, or in combination. Clinically, the 1550 nm laser is effective in the treatment of mild to moderate sagging and wrinkles, scars, and resurfacing. The 1927 nm laser improves skin texture and treats skin pigmentation and wounds. It can also be used for drug delivery. The selection and utilization rate of NAFL has been increasing in recent times, due to changes in lifestyle patterns and the need for beauty treatments with fewer side effects and short downtime. In this study, we present a plan for safe and effective laser therapy through a review of literature. Clinical applications of the multifunctional NAFL are also described.

• Journal of Welding and Joining
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• v.31 no.6
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• pp.71-76
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• 2013

Gas nitriding is a surface hardening process where nitrogen is introduced into the surface of a ferrous alloy. During fusion welding of nitrided carbon steel, the nitride inside weld metal is dissolved and generates nitrogen gas, which causes porosities - blow holes and pits. In this study, several laser welding processes such as weaving welding, two-pass welding, dual beam welding and laser-arc hybrid welding were investigated to elongate the weld pool to enhance nitrogen gas evacuation. The surface pits were successfully eliminated with elongated weld pool. However blowholes inside the weld metal were effective reduced but not fully disappeared.