• Proceedings of the IEEK Conference
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• 2001.06e
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• pp.215-218
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• 2001

A pulsed Nd:YAG laser is used widely for materials processing and medical instrument. It's very important to control the laser energy density in those fields using a pulsed Nd:YAG laser. A pulse repetition rate and a pulse width are regarded as the most dominant factors to control the energy density of laser beam. In this paper, the alternating charge and discharge system was designed to adjust a pulse repetition rate. This system is controlled by microprocessor and allows to frequence an expensive condenser for high frequency to cheap one for low frequency. In addtion, The microcontroller monitors the flow of cooling water, short circuit, and miss firing and so on. We designed Nd:YAG laser firmware with smart microcontroller, and want to explain general matters about the firmware from now.

• Proceedings of the IEEK Conference
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• 2001.06e
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• pp.211-214
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• 2001

For general laser power supply, the secondary of the power transformer is connected to the rectifier and filter capacitor. The output of a rectifier is connected to a switching element in the secondary of the transformer. So the Dower supply is complicated and the loss of switching is considerably. In addition, according to increasing pulse repetition, charged energy of energy-storage capacitor is not transferred sufficiently to flashlamp, and laser output efficiency decreases. In this raper, to improve laser efficiency, we designed and fabricated the power supply in which the SCR was turned on in zero point by the methods of ZCC(zero crossing control), PFN(pulse forming network) in result, laser output efficiency increased by hte 4% other than conventional supply, when a repetition rate was increased by the 10[pps], In 20(pps), efficiency was increased by about 8%

• Journal of IKEEE
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• v.14 no.2
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• pp.9-15
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• 2010

In this study, we have been proposed the new type of a transcranial magnetic stimulation adopted a variable voltage capacitor with Cockcroft-Walton circuit and constant-frequency current resonant half-bridge inverter. This a transcranial magnetic stimulation has some merits compared with the conventional one. First, it doesn't require the high voltage transformer. And second, it has less switching losses, compact size and capability in adjusting the transcranial magnetic stimulation output energy precisely. In this paper, we have performed the output characteristics of a transcranial magnetic stimulation system which is well known as magnetic stimulation. The tested results are described as a function of pulse repetition rate and switching numbers of the half-bridge inverter.

• Speech Sciences
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• v.1
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• pp.227-236
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• 1997

How do aphasics deal with the inflectional marking occurring in agglutinative languages like Korean? Korean speech repetition, comprehension and production were studied in 3 Broca's aphasic speakers of Korean. As experimental materials, 100 easy sentences were chosen in 1st grade Korean elementary school textbooks about reading writing and listening, and two pictures were made from each sentence. This study examines the use of three kinds of inflectional markings--past tense, nominative case, and accusative case. The analysis focuses on whether each inflectional marking was performed well or not in tasks such as repetition, comprehension and production. In addition, morphological errors concerned with each inflectional marking were analyzed in view of markedness. In general, the aphasic subjects showed a clear preservation of the morphological aspects of their native language. So the view of Broca's aphasics as agrammatical could not be strongly supported. It can be suggested that nominative case and accusative case are marked elements in Korean.

• Phonetics and Speech Sciences
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• v.7 no.3
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• pp.27-35
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• 2015

The purpose of this study is to examine the lexical representation of phonological variants derived from optional vs. obligatory phonological processes. Given that place assimilation is optionally processed, whereas nasal assimilation is obligatory in Korean, a long-term repetition priming experiment was conducted, using a shadowing task. Korean speakers shadowed words containing either assimilated or unassimilated consonants in three priming conditions and their shadow responses were evaluated. It was shown that in both place and nasal assimilations, shadowing latencies for unassimilated stimuli were longer than those for assimilated stimuli in the mismatched condition. These results suggest that even in the optional assimilation, assimilated variants were processed more easily and faster than the canonical variants. The present results argue against the frequency-based account of multiple lexical representation (Connine, 2004; Connine & Pinnow, 2006; Ranbom & Connine, 2007; $B{\ddot{u}rki$, Ernestus, & Frauenfelder, 2010; $B{\ddot{u}rki$, Alario, & Frauenfelder, 2011).

• Journal of the Optical Society of Korea
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• v.8 no.1
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• pp.29-33
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• 2004

We propose and demonstrate a novel optical pulse multiplier applicable to OTDM (Optical Time Division Multiplexing) systems using cascaded long-period fiber gratings. We have exploited the fact that each mode in a fiber has a different propagation constant to obtain time delays among optical pulses. The proposed scheme could realize high-frequency optical pulse multiplication for optical short pulse trains. We have successfully implemented two, four, and eight times multiplications with the maximum repetition rate of 416.7 ㎓. The obtained pulse delays are well matched with the simulated ones.

• Journal of Korean Vacuum Science & Technology
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• v.7 no.2
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• pp.45-56
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• 2003

A high flux metal plasma pulse ion source, which can simultaneously perform ion implantation and deposition, was developed and tested to evaluate its performance using the prototype. Flux of ion source was measured to be 5 A and bi-polar pulse power supply with a peak voltage of 250 V, repetition of 20 Hz and width of 100 ${\mu}\textrm{s}$ has an output current of 2 kA and average power of 2 kW. Trigger power supply is a high voltage pulse generator producing a peak voltage of 12 kV, peak current of 50 A and repetition rate of 20 Hz. The acceleration column for providing target energy up to ion implantation is carefully designed and compatible with UHV (ultra high vacuum) application. Prototype systems including various ion sources are fabricated for the performance test in the vacuum and evaluated to be more competitive than the existing equipments through repeated deposition experiments.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.12
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• pp.606-610
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• 2006

We investigated the output characteristics of Nd:YAG lasers at wavelength of 1444 nm, which were pumped by 450 Xe-flashlamp, 700 torr Xe-flashlamp and 700 torr Kr-flashlamp. With a Xe-flashlamp of 700 torr of gas pressure, the pulse energy of 0.738 J was obtained with repetition rate of 9.16 Hz and pumping pulse width of 400 ms. In case pumping pulse width of 5 ms and repetition rate of 1 Hz, 700 torr Kr-flashlamp showed the highest pulse energy of 1.44 J.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.3
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• pp.453-460
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• 2010

For high quality image acquisition, compensating air-vehicle motion is essential for airborne SAR system. This paper describes a timing control based motion compensation method for airborne SAR system. Efficient timing control is critical for SAR system since it maintains many timing signals and timing setting for the signals should be updated frequently. This paper proposes Timing Cluster method as an efficient means for timing control of SAR system. Moreover, this paper suggests a simple and efficient method to compensate air-vehicle motion based on the Timing Cluster method. Timing Cluster method enables SAR system to control the timing in a timing noncritical way just maintaining little amount of information.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1729-1731
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• 2003

Recently many solid-state laser systems were widely used in the medical applications. So it is necessary to study various optimal laser parameters for adopting new medical treatments. Alexandrite laser using switching mode power supply has designed and experimented to adjust a pulse repetition rate by PIC one-chip microprocessor. The fundamental results have been obtained during the first financial year in 2002. We will be able to find out the optimal hair removal characteristics by the repetitive experiments of Alexandrite laser as the parameters such as pulse repetition rate, pulse width, and pulse energy etc.