• Journal of Welding and Joining
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• v.20 no.4
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• pp.525-534
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• 2002

During laser spot welding of the braun tube electron gun, phenomena such as serious spattering and oxidative reaction, etc. were occurred. The spatter occurred from weld pool affects the braun tube, namely it blocks up a very small hole on the shadow mask and causes short circuit between two roles of the electron gun. We guessed that high power density and oxidative reaction are main sources of these problems. So, we studied to prevent and to reduce spatter occurring in spot welding of the braun tube electron gun using pulsed Nd:YAG laser. The characteristics of laser output power was estimated, and the loss of laser energy by optical parameter and spatter was measured by powermeter. The effects of welding parameters, laser defocused distance and incident angle, were investigated on the shape and penetration depth of the laser welded bead in flare and flange joints. From these results, the laser peak power was a major factor to control penetration depth and to occur spatter. It was found that the losses of laser energy by optic parameter and sticked spatter affect seriously laser weldability of thin sheets. The deepest penetration depth is gotten on focal position, and a "bead transition" occurred with a slight displacement of focal position relative to the workpiece surface and the absorption rate of the laser energy is affected by the shape factor of the workpiece. When we changed the incident angle of laser beam, the penetration depth was decreased a little with increasing of the incident angle, and the bead width was increased. The spattering was prevented by considering laser beam energy and incident angle.ent angle.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.3
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• pp.453-460
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• 2014

Fault injection attack is the process of attempting to acquire the information on-chip through inject artificially generated error code into the cryptographic algorithms operation (or perform) which is implemented in hardware or software. From the details above, the laser-assisted failure injection attacks have been proven particularly successful. In this paper, we propose an improved laser probing system for fault injection attack which is called the Dual-Laser FA tool set, a hybrid approach of the Flash-pumping laser and fiber laser. The main concept of the idea is to improve the laser probe through utilizing existing equipment. The proposed laser probe can be divided into two parts, which are Laser-I for laser cutting, and Laser-II for fault injection. We study the advantages of existing equipment, and consider the significant parameters such as energy, repetition rate, wavelength, etc. In this approach, it solves the high energy problem caused by flash-pumping laser in higher repetition frequency from the fiber laser.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.1
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• pp.90-95
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• 2014

The system design and the system performance analysis of 3D imaging laser radar system for the mapping purpose is addressed in this article. For the mapping, a push-bloom scanning method is utilized. The pulsed fiber laser with high pulse energy and high pulse repetition rate is used for the light source of laser radar system. The high sensitive linear mode InGaAs avalanche photo-diode is used for the laser receiver module. The time-of-flight of laser pulse from the laser to the receiver is calculated by using high speed FPGA based signal processing board. To reduce the walk error of laser pulse regardless of the intensity differences between pulses, the time of flight is measured from peak to peak of laser pulses. To get 3D image with a single pixel detector, Risley scanner which stirs the laser beam in an ellipsoidal pattern is used. The system laser energy budget characteristics is modeled using LADAR equation, from which the system performances such as the pulse detection probability, false alarm and etc. are analyzed and predicted. The test results of the system performances are acquired and compared with the predicted system performance. According to test results, all the system requirements are satisfied. The 3D image which was acquired by using the laser radar system is also presented in this article.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.5
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• pp.74-81
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• 2019

This study reports the CW $CO_2$ laser scribing of soda lime glass. In this study, scribing experiments are carried out at different laser powers, scan speeds, and focal positions to investigate the effect of the process parameters on the interaction characteristics between a laser beam and glass. In particular, the interaction characteristics are analyzed and described with the input laser energy per unit length. According to the experimental results, the damage threshold for the glass surface was found to exist between 0.072 and 0.08 J/mm. The input laser energy in this region induced partial melting of the surface and grain-shaped cracks. These cracks tended to increase as the input laser energy increased. At the laser input energy larger than 1 J/mm, a huge crack propagating along the scan direction was produced, and the volume below the scribed area was fully melted. The growth of this crack finally resulted in the complete cutting of the glass at the input laser energy above 8 J/mm. It was found that both the width and depth of the scribed line increased with increasing input laser energy. For the beam focusing at the rear surface, the width of the scribed line varied irregularly. This could be ascribed to the increased asymmetry of the beam intensity distribution when the laser beam was focused at the rear surface. Under this condition, a large burr was only produced on one side of the scribed line.

• Medical Lasers
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• v.10 no.4
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• pp.207-213
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• 2021

Background and Objectives This study was undertaken to assess the stability and efficacy of laser therapy (808 nm), Liquiband (a commercial topical skin adhesive product), and a combination treatment, for application in oral ulcers. Materials and Methods The oral ulcer rat animal model was used to determine the efficacy of photobiomodulation, Liquiband, or combination therapy. Ulcers were induced by injecting 60% acetic acid in the oral mucosa. Three days after ulcer confirmation, the chemically induced ulcers were treated with either laser (808 nm), Liquiband, or a combination of both, every two days for 8 days (4 sessions). Combination therapy was performed by first treating with laser followed by application of the Liquiband. Reduction in ulcer area size was subsequently determined, and animals were sacrificed at 5 and 10 days after the last administration, for histological observation of the extracted oral ulcer tissue samples. Results In this study, treatment with either laser (808 nm) or commercial Liquiband product as well as the combined treatment significantly enhanced oral ulcer healing in the rat animal model. The effect of laser treatment is mainly attributed to collagen synthesis, whereas application of the Liquiband promotes vascularization and formation of granulation tissue. Our results indicate that further optimization of the combined therapy could synergistically and significantly enhance oral ulcer healing. Conclusion Laser or Liquiband treatment of oral ulcer in the rat animal model exert different outcomes, but both methods confirm significant effects relative to the untreated group. The combined treatment group with laser and Liquiband showed marked oral ulcer healing, but further optimization is required to get highly significant results and establish the potential synergistic effect of the combination therapy, as compared to the individual enhancing effects of healing oral ulcers.

• The Journal of the Society of Stroke on Korean Medicine
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• v.6 no.1
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• pp.9-16
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• 2005

Objective : The heart rate variability is very useful indicator to study the function of the autonomic nervous system(ANS), and the physiologic signals can be observed based on the changes of the ANS of the heart. In order to assay the effects of the laser exposing to healthy subjects, the double blind test has been performed. Methods : This study included 62 healthy adults who have not any ANS disease and had normal sinus rhythm in electrocardiogram. The control group consisted of 31 subjects, laser group consisted of 31 subject. HRV was measured for 5 minutes before laser irradiation, sham and real laser irradiated for 30 minutes and than HRV remeasured for 5 minutes. Statistical significance was evaluated by independent T-test. Results : Mean HRV, Ln(VLF), Ln(HF), Ln(TP) of both groups at post-laser period decreased compared with that of the pre-laser period. Ln(LF) of both groups at post-laser period increased compared with that of the pre-laser period. LF/HF, SDNN of real laser group decreased and sham group decreased. Conclusions : There is no difference between two groups. The reason is presumed that all the studied subjects are healthy adults, and also the short and single transcutaneous laser irradiation would not influence upon changes of the ANS. The further study must be followed.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2003.05a
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• pp.56-59
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• 2003

• Korean Journal of Animal Reproduction
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• v.22 no.3
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• pp.287-292
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• 1998

The objective of this study was to test whether ZP drilling using a 1.48$\mu$m diode laser beam on mouse IVF embryos becomes effective the hatching and normal in vivo development, as a preliminary test for obtaining the additional proof that the 1.48$\mu$m diode laser could be used safely for human applications. The results obtained in this experiment were as follows: when the hatched rates of mouse embryos by laser ZP drilling according to the embryonic stage were examined until 72 hr (in case of blast tocyst: day 4 after IVF) or 120 hr (in case of 4-cell: day 2 after IVF) after treatment, the d data of laser drilled blastocysts (81.8%) was significantly higher than those of control (hatching blastocyst: day 4 after IVF) (54.2%) and laser drilled 4-cell embryos (45.5%) (p<0.05). When the effect of laser drilling on implantation rates following embryo transfer in day 3 synchronized pseudopregnant recipients was examined, the l laser drilled group (48.7%) was slightly higher than that of control group (43.6%). In addition, when the several pregnant mice delivered in two groups were analysed their chromosomal normality and tested reproductive ability, all p pups were presented normal chromosomal number (n=40) and showed normal growth and reproductive ability. Therefore, these results dem-onstrated that ZP drilling using a 1.48$\mu$m diode l laser can increase the embryo hatching and ind duce the normal pregnancy of mouse embryos.

• Korean Journal of Acupuncture
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• v.34 no.1
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• pp.56-69
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• 2017

Objectives : The purpose of this study is to compare the effects of laser acupuncture to the 532 nm on the five transport points with the heart meridian for treatment to hypertensive disease in rats with L-NAME induced hypertensive. Methods : Hypertensive was induced by L-NAME for 3 weeks. The laser acupuncture therapy on the five transport points of heart meridian(Laser Well Point-HT9, Laser Brook Point-HT8. Laser Stream Point-HT7, Laser River Point-HT4 and Laser Sea Point-HT3) was treated twice a week for 5 times. The hypertensive was measured using a cardiac hypertrophy, atherogenic index, TG/HDL-cholesterol ratio, TCHO, HDLC, TG, AST, ALT, antioxidative effectiveness and glutathione peroxidase quality of hypertensive rats induced by L-NAME. Results : Blood pressure were decreased significantly after the laser acupuncture of Well, Brook and Sea Point groups. Cardiac hypertrophy were decreased at the laser acupuncture of Brook and Stream Point groups. Athrogenic index was decreased at the laser acupuncture of Well, Stream, River and Sea Point groups. TG/HDL-cholesterol ratio was decreased at the laser acupuncture of all groups. Total cholesterol was decreased significantly at the laser acupuncture of Well Point group. High density lipoprotein cholesterol and total cholesterol were decreased significantly at the laser acupuncture of Well, Stream and River Point groups. Triglyceride was decreased significantly at the laser acupuncture of Stream Point group. Cu/Zn-Superoxide Dismutase (Cu/Zn-SOD) and glutathione peroxidase(GPX) were increased significantly at the laser acupuncture of Well Point group. Conclusions : The laser acupuncture treatment in five transport points of the Heart Meridian was effective for lowering blood pressure, cardiac hypertrophy, Atherogenic index and HTR, and for enhancing antioxidant activity.

• Laser Solutions
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• v.15 no.1
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• pp.20-22
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• 2012

This papers show new technology of thin disk type resonator lasers which are well kwon technology by TRUMPF.