• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 E
• /
• pp.2204-2206
• /
• 1999

Pulsed Nd:YAC laser is used widely for materials processing and instrumentation. It is very important to control the laser energy density in materials processing by 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 study, the alternating charge-discharge system was designed to adjust a pulse repetition rate. This system is controlled by one chip microprocessor and allows to replace an expensive condenser for high frequency to a cheap condenser for low frequency. In addition. we have investigated the current pulse shape of flashlamp and the operating characteristics of a pulsed Nd:YAG laser. As a result, it is found that the laser output of the power supply using the alternating charge-discharge system is not less than that of typical power supply. As the pulse repetition rate rises from 30pps to 120pps by the step of 30pps at 1200V, it is found that the laser efficiency decreases but the laser output power increases about 6W at each step.

• 대한음성학회지:말소리
• /
• 제58호
• /
• pp.1-18
• /
• 2006

The purpose of this study was to investigate diadochokinetic (DDK) characteristics in the subjects with spastic cerebral palsy (CP) by severity. DDK characteristics were measured through rate, regularity, accuracy and consistency in Alternate Motion rate (AMR) and Sequential Motion rate (SMR) tasks. The subjects participated in this study included 27 subjects with spastic CP (mild- 9, moderate- 9, severe- 9) and 9 normal persons who are around 11-20 years old. On the result of this study, rate in AMR was significant difference between all spastic groups and normal group, and rate in SMR was significant difference between normal and mild groups and moderate and severe groups. In regularity of the DDK tasks, severe group had significant difference the other groups. Finally, accuracy and consistency of the DDK tasks exhibited significant difference between all spastic groups and normal group. In conclusion, the subjects with spastic CP have a tendency to produce slow and irregular syllable repetition as severity increases, but to produce inaccurate and inconsistent syllable repetition regardless of severity in the DDK tasks.

• 대한의용생체공학회:의공학회지
• /
• 제35권3호
• /
• pp.62-67
• /
• 2014

The purpose of the study was to identify the effect of laser parameters on photocoagulation to maximize safety and efficacy during varicose vein treatment. CW and pulsed modes at 1470 nm were initially compared as a function of power on bovine liver tissue. In the pulsed mode, various parameters including repetition rate, duty cycle, and irradiation time were compared to evaluate tissue response during thermal treatment. The results demonstrated that CW and pulsed modes yielded almost similar coagulation development possibly due to shorter irradiation time of 5 sec. Regardless of laser mode, both repetition rate and duty cycle presented constant coagulation rate whereas longer irradiation time facilitated coagulation process.

• 한국염색가공학회지
• /
• 제16권6호
• /
• pp.16-22
• /
• 2004

This study was carried out to investigate K/S values, surface color, the fastness to washing, bacteria reduction rate of the silk and cotton fabrics dyed with Rhus verniciflua extract under the various dyeing conditions. The optimum dyeing temperature, dyeing time, dyeing pH and repetition of the silk fabrics dyed with Rhus verniciflua extract were $l00^{\circ}C, 30min., pH 5, five times repetition respectively, but in the cotton fabrics, it were $60^{\circ}C . 30min., pH 7, one times repetition. It were colored orangish Yellow in the silk fabrics and colored bright yellow in the cotton fabrics dyed with Rhus verniciflua extract. Surface color(munsell value) was not changed by the mordanting agents but those of the silk showed high tone when mordanting with stannous chloride, and it was decolored and darked when mordanting with ferric sulfate. The fastness to washing in the silk fabrics dyed with mordanting agents improved in 4～5 grade, but the cotton fabrics were 3～4 grade, so washing fastness of the silk and cotton fabrics were significantly improved when washing with the neutral detergent. The bacteria reduction rate of the silk fabrics increased drastically by dyeing of Rhus verniciflua extract.

• 전기학회논문지
• /
• 제64권8호
• /
• pp.1207-1211
• /
• 2015

Various laser systems have been widely used in almost all industrial technologies because they have high energy density, directivity and coherence. Recently the clinical application is becoming wider in medical parts such as incurable disease, diagnosis and so on. Generally, ruby laser beam has the greatest efficacy for removing tattoos, freckle and other skin problem. But current medical ruby laser system has the maximum repetition rate of 2Hz and optical output beam energy of 1J. Many medical doctors really want to have a high repetition ruby laser system because that can reduce the operation time. We investigated a new ruby laser system with high repetition rate of 4Hz using double cavities. Furthermore, we develop a new power supply system adopting zero voltage switching(ZVS) to minimize switching loss by LLC resonant converter designed as 2kW class.

• 전기학회논문지
• /
• 제64권5호
• /
• pp.746-750
• /
• 2015

In this paper, we propose a simulator to evaluate the performance of the semi-active laser guidance or the quadrant photodetector and to simulate the laser power reflected from a target. The laser pulse repetition frequency was generated and synchronized with the laser pulse repetition(PRF) code. To evaluate the performances of the proposed methods, we implemented a prototype system and performed experiments. As a result, the generated high voltage was variable in the range of DC 3V to 340V and has the rate of change of 2000 V/s. PRF code can be generated within 50ms ∼ 100ms and the error is implemented within 0.3ns. The laser output is synchronized with the PRF code and has a dynamic range of 23.6dB.

• 한국통신학회논문지
• /
• 제28권12C호
• /
• pp.1192-1199
• /
• 2003

본 논문에서는 다중경로 채널 환경에서 펄스 반복 빈도 (pulse repetition frequency, PRF)와 슬롯 시간이 UWB (ultra wide band) 무선 통신 시스템의 데이터 전송율 (throughput) 성능에 미치는 영향을 조사하고 이를 기반하여 유효 데이터 전송율이 최대화되도록 하는 PRF와 슬롯 시간을 이용한 전송율 제어를 제안한다. 최근에 UWB 시스템이 갖고 있는 장점으로 인하여 근거리 고속 무선 데이터 전송과 관련하여 관심이 고조되고 있다. UWB 시스템에서는 데이터 전송율을 결정짓는 파라미터로는 펄스를 반복하는 펄스 반복 회수와 펄스간의 간격을 결정짓는 슬롯 시간을 들 수 있다. AWGN이 존재하는 다중경로 채널 하에 있는 UWB 시스템은 펄스간의 간섭(inter-pulse interference, IPI)과 잡음에 의하여 시스템 성능이 저하된다. UWB 시스템은 이 두 파라미터의 조정을 통하여 시스템의 성능을 유지 또는 개선할 수 있다. 본 논문에서는 두 파라미터의 변화가 다양한 채널 환경에서 데이터 전송율에 미치는 영향을 모의실험을 통하여 관측하고 이를 기반하여 설계된 가변 전송율을 사용하는 것이 비가변적인 방법에 비하여 유효 데이터 전송율 측면에서 우수함을 모의실험을 통하여 검증하였다.

• 한국지역사회생활과학회지
• /
• 제18권3호
• /
• pp.391-398
• /
• 2007

Ginkgo leaves, which have been known as medical materials, were selected as new natural dyes in this study, in which it was examined whether they have the function of UV-blocker or not. Cotton, linen & Hanji(Korean traditional paper) were dyed with Ginkgo. Al, Cr, Cu, Fe and Sn were selected as mordants. UV-blocking rate of dyed samples was measured after dyeing and mordant treatment. The results of this study are as follows. First, most surface color of dyed samples was yellow except that Hanji mordanted with Cu was yellowish red. Second, dyeing repetition had positive correlations with K/S values of cotton ($r=.\;758^{**}$), linen ($r=.\;500^*$) and Hanji ($r=.\;819^{**}$), because K/S values were increased according to dyeing repetition. Third, solar UV-blocking rates had positive correlations with dyeing repetitions (p<0.01), because UV-blocking rates had increased according to dyeing repetition. Fourth, UV-blocking ability of Hanji was highest among samples, as UV-blocking rates of cotton and linen dyed after 3 dyeing repetition were up to 93%, Hanji's values were up to 98%. Therefore, it was proven that Ginkgo extracts used in this experiment as dyestuff have excellent dyeing ability and high UV-blocking ability. It is hoped that this work will lead to further research to confirm the physiological effects when human wear the clothes made from Hanji.

• 한국콘텐츠학회논문지
• /
• 제13권2호
• /
• pp.308-313
• /
• 2013

본 연구는 자기공명영상장치의 특성변수인 숙임각(flip angle), 반복시간(repetition time, TR), 에코시간(echo time, TE)을 사용하여 전자파흡수율(specific absorption rate, SAR)을 알아보고자 하였다. 연구대상은 체중 10 kg부터 90 kg까지를 대상으로 하여 동일한 검사기법을 적용하였고, 매개변수의 변화에 따른 평균 SAR 및 peak SAR 값을 측정하였다. 체중에 따른 SAR는 TE에서 변화는 없지만 숙임각이 커지고 TR이 짧을수록 증가하였다. SAR 값은 두부 허용 기준치 범위에 포함이 되었고 분절별 체중에 따른 영상의 신호 대 잡음비(signal to noise ratio, SNR)는 체중이 증가함에 따라 SNR은 증가하지는 않았다. 본 결과를 바탕으로 적절한 특성변수를 사용하여 다양한 대조도와 SNR을 얻어 진단의 가치를 높일 수 있을 것이다.

• 전기전자학회논문지
• /
• 제15권4호
• /
• pp.305-312
• /
• 2011

A primary interest of this work is to develop an efficient and powerful repetitive pulser system for the application of ultra wide band generation. The important component of the pulser system is a small-sized coaxial type spark gap with planar electrodes filled with SF6 gas. A repetitive switching action by the coaxial spark gap generates two consecutive pulses in less than a microsecond with rise times of a few hundred picoseconds (ps). A set of several parameters for the repetitive switching of the spark gap is required to be optimized in charging and discharging systems of the pulser. The parameters in the charging system include a circuit scheme, circuit elements, the applied voltage and current ratings from power supplies. The parameters in the discharging system include the spark gap geometry, electrode gap distance, gas type, gas pressure and the load. The characteristics of the spark gap discharge, such as breakdown voltage, output current pulse and recovery rate are too dynamic to control by switching continuously at a high pulse repetition rate (PRR). This leads to a low charging efficiency of the spark gap system. The breakthrough of the low charging efficiency is achieved by a parallel operation of two spark gaps system. The operational behavior of the two spark gaps system is presented in this paper. The work has focused on improvement of the charging efficiency by scaling the PRR of each spark gap in the two spark gaps system.