• Journal of Korea Society of Digital Industry and Information Management
• /
• v.5 no.4
• /
• pp.1-9
• /
• 2009

It establishes the nonlinear optics material recently on solid-state laser output side and from the infrared ray until is early has in the ultraviolet rays and the wavelength of broadband there makes be a possibility of getting the laser light which and in processing and measuring field it is widely used. Consequently, it used the pulse reiteration law from origination and nine as the fundamental wave direct plan it produced. intense it affixed the nonlinear optics material (KTP) in pulsed light and it got the green light. When inflicting a same energy in respectively reiteration mesh, intense interrelation of pulse light output and green light output between. It analyzed the conversion ratio which it follows in the mesh.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.1472-1473
• /
• 2007

In this paper, it is investigated to develop a compact 150kJ pulsed power supply to be operated on a vehicle. The goals of development are the maximum charging energy of 150kJ, the efficiency of energy transfer of >80%, the pulse forming of trapezoidal wave of $150{\sim}250MW$, the consecutive charging rate of >several shots/min. The hierarchy and circuit of the pulsed power supply for optimization, high efficiency and minimization of volume are investigated and presented. And, the charging voltage, inductance and resistance of the compact pulsed power supply are studied and determined.

• Laser Solutions
• /
• v.6 no.3
• /
• pp.37-45
• /
• 2003

Pulsed laser ablation is important in a variety of engineering applications involving precise removal of materials in laser micromachining and laser treatment of bio-materials. Particularly, detailed numerical simulation of complex laser ablation phenomena in air, taking the interaction between ablation plume and air into account, is required for many practical applications. In this paper, high-power pulsed laser ablation under atmospheric pressure is studied with emphasis on the vaporization model, especially recondensation ratio over the Knudsen layer. Furthermore, parametric studies are carried out to analyze the effect of laser fluence and background pressure on surface ablation and the dynamics of ablation plume. In the numerical calculation, the temperature, pressure, density, and vaporization flux on a solid substrate are obtained by a heat-transfer computation code based on the enthalpy method. The plume dynamics is calculated considering the effect of mass diffusion into the ambient air and plasma shielding. To verify the computation results, experiments for measuring the propagation of a laser induced shock wave are conducted as well.

• The Journal of the Acoustical Society of Korea
• /
• v.23 no.7
• /
• pp.514-520
• /
• 2004

There are many techniques for underwater source localization. These are the methods based on TDOA (Time Difference Of Arrival) estimation. beamforming techniques and high resolution techniques, etc. In this Paper we estimate the underwater source position using MCPSP (Modified Cross Power Spectrum Phase) function that is calculated on frequency domain using sensors of small number. However, the performances of the localizing method based on MCPSP function drops greatly in the case of CW (Continuous Wave) signal . In this Paper we proposed the TDOA estimation method for pulsed CW signal. In the Proposed method we composed of new segment including a edge of ping. This segment was computed by short-time energy detection. With theoretical representation the performances of the proposed method were analyzed under various environment.

• Journal of the Korean Vacuum Society
• /
• v.5 no.3
• /
• pp.229-238
• /
• 1996

The electromigration phenomena and the characterizations of the conductor lifetime (Time-To-Failure, TTF) in Al-1%Si thin film interconnections under D.C. and Pulsed D.C. conditions were investigated . Meander type test patterns were fabricated with the dimensions of 21080$mu \textrm{m}$ length, 3$\mu\textrm{m}$ width, 0.7$\mu\textrm{m}$ thickness and the 0.1$\mu\textrm{m}$/0.8$\mu\textrm{m}$($SiO_2$/PSG)dielectric overlayer. The current densities of $2 \times10^6 A/\textrm{cm}^2$ and $1 \times10^7 A/\textrm{cm}^2$ were stressed in Al-1%Si thin film interconnection s under a D.C. condition. The peak current densities of $2 \times10^6 A/\textrm{cm}^2$ and $1 \times10^7 A/\textrm{cm}^2$ were also applied under a Pulsed D.C. condition at frequencies of 200KHz, 800KHz, 1MHz, and 4MHz with the duty factor of 0.5. THe time-to-failure under a Pulsed D.C.($TTF_{pulsed D.C}$) was appeared to be larger than that under a D.C. condition. It was found that the TTF under both a D.C. and a Pulsed D.C. condition. It was found that the TTF under both a D.C. and a Pulsed D.C. condition largely depends upon the appiled current densities respectively . This can be explained by a relaxation mechanism view due to a duty cycle under a Pulsed D.C. related to the wave on off. The relaxation phenomena during the pulsed off period result in the decayof excess vacancies generated in the Al-1%Si thin film interconnections because of the electrical and mechanical stress gradient . Hillocks and voids formed by an electromigration were observed by using a SEM (Scanning Electron Microscopy).

• Journal of Sensor Science and Technology
• /
• v.27 no.5
• /
• pp.328-334
• /
• 2018

The paper reviews an improved continuous-wave (CW) terahertz (THz) imaging system developed for nondestructive inspection, such as CW-THz quasi-time-domain spectroscopy (QTDS) and interferometry. First, a comparison between CW and pulsed THz imaging systems is reported. The CW-THz imaging system is a simple, fast, compact, and relatively low-cost system. However, it only provides intensity data, without depth and frequency- or time-domain information. The pulsed THz imaging system yields a broader range of information, but it is expensive because of the femtosecond laser. Recently, to overcome the drawbacks of CW-THz imaging systems, many studies have been conducted, including a study on the QTDS system. In this system, an optical delay line is added to the optical arm leading to the detector. Another system studied is a CW-THz interferometric imaging system, which combines the CW-THz imaging system and far-infrared interferometer system. These systems commonly obtain depth information despite the CW-THz system. Reportedly, these systems can be successfully applied to fields where pulsed THz is used. Lastly, the applicability of these systems for nondestructive inspection was confirmed.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2006.05a
• /
• pp.268-271
• /
• 2006

We have studied the backward wave oscillator, a power-pulsed generator oscillator at 20 GHz has higher frequency then current one. An absolute instability linear analysis was used for the purpose of designing the slow wave structure. A large diameter of the slow wave structure was adopted to prevent the breakdown brought about by the increase of power density.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.851-856
• /
• 2003

This paper proposes a single-mode Lamb-wave generation and detection system using a pulsed laser as a generator and an air-coupled transducer combined with the wavelet transform analysis, as the detector. The laser source with arrayed linear slits was used to generate Lamb-wave which is able to control the wavelength of Lamb-wave to be generated by changing the slits separation. An ari-coupled transducer was used to receive Lamb-wave, which can selectably receive a single mode of leaky Lamb wave by changing the oblique angle of transducer, since the leaky Lamb-wave has unique leaky-angle according to the mode. Also, the received signal was processed by wavelet transform for the analysis in domain of time-frequency. The theoretical dipersion curve and the experimetal result was compared to show good agreement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.812-819
• /
• 2007

Acoustic Target Strength (TS) is a major parameter of the active sonar equation, which indicates the ratio of the radiated intensity from the source to the re-radiated intensity by a target. This research provides the time pattern of TS in time domain, which is applicable to pulse modulated acoustic pressure field. If the time pattern of TS is predicted by using TS equation in frequency domain, it takes long time and difficult since time function pulsed acoustic wave may be decomposed into their frequency domain components. But TS equation in time domain has a convenience. If the expression for pulsed acoustic field has been obtained, the problem can be solved. Furthermore this paper introduces about mathematical equivalence quantities between EM wave and Acoustic Wave.

• Journal of Adhesion and Interface
• /
• v.10 no.1
• /
• pp.17-22
• /
• 2009

Polymer thin films were prepared by radio frequency (RF) plasma polymerization of phthalic anhydride (PA). First, monomer vaporization temperature ($100{\sim}160^{\circ}C$) was optimized by evaluating the thermal properties of thin films using differential scanning calorimeter (DSC) and measuring the root-mean-square (RMS) roughness with atomic force microscope (AFM) at the fixed plasma power of 10 W and time of 5 min in a continuous-wave (CW) mode. Plasma power (5~20 W) was then optimized by measuring the film solubility in solvents such as toluene, acetone, dimethylsulfoxide (DMSO) and 1 methylpyrrolidine (NMP). Next, pulsed mode plasma polymerization was also studied by varying the duty cycle of on-time (5, 20%) under optimized conditions of continuous-wave (CW) mode ($120^{\circ}C$, 10 W) in order to increase the anhydride functional groups. Finally, polymer thin films were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyzer (TGA) and ${\alpha}$-step.