• Current Optics and Photonics
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• 제6권4호
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• pp.407-412
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• 2022

We report on a diode-laser-pumped mode-locked Yb:KGW laser system, which delivers ultrashort pulses down to 89 fs at a repetition rate of 63 MHz, with an average power of up to 5.6 W. A fiber-coupled diode laser at 981 nm, operated with a compact driver, is used to optically pump the gain crystal via an off-axis parabolic mirror. A semiconductor saturable-absorber mirror is used to initiate the pulsed operation. Laser characteristics such as the pulse duration, spectrum bandwidth, and output power are investigated by varying the intracavity dispersions via changing the number of bounces between negative-dispersive mirrors within the cavity. Short pulses with a duration of 89 fs, a center wavelength of 1,027 nm, and 3.6 W of output power are produced at a group-velocity dispersion (GVD) of -3,300 fs². As the negative GVD increases, the pulse duration lengthens but the output power at the single-pulse condition can be enhanced, reaching 5.6 W at a GVD of -6,600 fs². Because of pulse broadening at high negative GVDs, the highest peak intensity is achievable at a moderate GVD with our system.

• Journal of Astronomy and Space Sciences
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• 제37권2호
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• pp.143-156
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• 2020

Korea Polar Research Institute (KOPRI) installed an ionospheric sounding radar system called Vertical Incidence Pulsed Ionospheric Radar (VIPIR) at Jang Bogo Station (JBS) in 2015 in order to routinely monitor the state of the ionosphere in the auroral oval and polar cap regions. Since 2017, after two-year test operation, it has been continuously operated to produce various ionospheric parameters. In this article, we will introduce the characteristics of the JBS-VIPIR observations and possible applications of the data for the study on the polar ionosphere. The JBS-VIPIR utilizes a log periodic transmit antenna that transmits 0.5-25 MHz radio waves, and a receiving array of 8 dipole antennas. It is operated in the Dynasonde B-mode pulse scheme and utilizes the 3-D inversion program, called NeXtYZ, for the data acquisition and processing, instead of the conventional 1-D inversion procedure as used in the most of digisonde observations. The JBS-VIPIR outputs include the height profiles of the electron density, ionospheric tilts, and ion drifts with a 2-minute temporal resolution in the bottomside ionosphere. With these observations, possible research applications will be briefly described in combination with other observations for the aurora, the neutral atmosphere and the magnetosphere simultaneously conducted at JBS.

• 한국임상수의학회지
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• 제32권4호
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• pp.301-307
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• 2015

본 연구의 목적은 적색 형광 단백질 유전자 형질 전환 복제견을 포함한 복제견들에서 측정된 심장 초음파 수치를 이전에 보고된 일반개의 정상 참고 범위와 비교하는 것이다. 일곱 마리의 복제견에서 M-mode, 2D-mode, pulsed wave Doppler 그리고 Tissue Doppler Imaging을 통해 좌심, 우심 그리고 우심실 우출로의 해부학적 특징과 심장 기능을 평가하였다. 모든 복제견들은 해부학적 구조에서 특이적인 이상을 나타내지 않았으며 측정된 수치들은 정상 참고 범위 이내에 있었다. 게다가 좌심과 우심의 심근 기능 모두 정상 참고 범위 이내에 위치하였다. 특히 복제 동물들에서 흔히 나타나는 우심 부전과 폐성 고혈압은 복제견들에서는 나타나지 않았다. 결론적으로, 성장이 끝난 복제견들에게서 는 출생시와 성장과정에서 심혈관계의 이상을 타나내는 징후는 확인되지 않았다. 그러므로 형질 전환 방법을 포함하는 체세포핵이식 기술은 복제견들의 심장 형태와 기능에 대해 심각한 부작용을 나타내지 않는다고 할 수 있다.

• 대한의용생체공학회:의공학회지
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• 제19권4호
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• pp.379-384
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• 1998

본 연구에서는 초음파를 이용하여 피부 혈관에서 그 위치에 대한 혈류 신호정보를 얻을 수 있는 펄스파(pulsed wave) 시스템을 이 분야에 응용하기 위한 가능성을 고찰하였다. 20MHz의 변환자로 수신된 신호들은 시간 영역에서 서로 비교하여 편이량을 cross-correlation방법을 사용하여 혈류속도를 구하였다. 피부의 매우 작은 혈관에서 혈류속도 거출시 발생되는 문제점에 대해 in-vitro와 in-vivo 실험을 통해서 이 방법의 효용성을 보이고 그 문제점에 대한 해결 방법을 제시한다. 시간 편이량 측정은 cross-correlation방법에 의해 정규화된 계수에서 최대점을 찾는 것이며 송신주기에 따라 반사된 수신 신호에서부터 cross-correlation방법을 사용하여 속도를 구한다. In-패패 실험을 통해 작은 튜브 내의 깊이에 대한 속도 정보를 주는 속도 profile과 이론적으로 계산된 속도 rpofile을 비교하였으며 토끼 귀 부분의 auriculares caudales에서 소동맥과 소정맥에 대한 혈류속도 profile을 구하였다. 수신 신호에서 진동에 의한 오차는 DFT를 사용하여 보정하였고 클루터 신호는 전체 수신 신호를 평균하여 하나의 기준 수신 신호를 정하여 이것에서 다른 수신 신호 값을 뺌으로써 감소시켰다.

• 한국정보통신학회논문지
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• 제17권10호
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• pp.2359-2368
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• 2013

본 논문에서는 power IC에서 파워가 ON되어있는 동안 입력 신호인 RD(Read) 신호 포트에 glitch와 같은 신호 잡음이 발생하더라도 파워-업(power-up)시 readout된 DOUT 데이터를 유지하면서 다시 읽기 모드로 재진입하지 못하도록 막아주는 IRD(Internal Read Data) 회로를 제안하였다. 그리고 pulsed WL(Word-Line) 구동방식을 사용하여 differential paird eFuse OTP 셀의 read 트랜지스터에 수 십 ${\mu}A$의 DC 전류가 흐르는 것을 방지하여 blowing 안된 eFuse 링크가 EM(Electro-Migration)에 의해 blowing되는 것을 막아주어 신뢰성을 확보하였다. 또한 program-verify-read 모드에서 프로그램된 eFuse 저항의 변동을 고려하여 가변 풀-업 부하(variable pull-up load)를 갖는 센싱 마진 테스트 기능을 수행하는 동시에 프로그램 데이터와 read 데이터를 비교하여 PFb(pass fail bar) 핀으로 비교 결과를 출력하는 회로를 설계하였다. $0.18{\mu}m$ 공정을 이용하여 설계된 8-비트 eFuse OTP IP의 레이아웃 면적은 $189.625{\mu}m{\times}138.850{\mu}m(=0.0263mm^2)$이다.

• Journal of Oral Medicine and Pain
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• 제25권4호
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• pp.415-425
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• 2000

In order to obtain the basic data concerning the optimal lasing conditions in using Nd:YAG laser as an adjunctive modality of periodontal therapy of root planing without irreversible structural deterioration of cervical cementum, the author selected 36 human teeth having no cervical abrasion and caries (; 12 anteriors, 12 premolars. 12 molars) extracted due to periodontal diseases, and divided them into 4 groups as Group I, II, III and IV (; each group of 3 anteriors, 3 premolars, 3 molars), and prepared a cementum specimen with thickness of $1.0mm{\pm}0.2mm$ sectioned longitudinally at the middle of mesio-distal thickness (; Group I) or horizontally at 1mm-2mm below the cemento-enamel junction (; Group II, III, IV) from each tooth of each group by low speed diamond wheel saw, and treated them with 0.5 M ethylene diamine tetraacetic acid (; EDTA, pH=7.4) for 2 minutes for elimination of remnants during tooth-sectioning. And the author applied the laser energy from a fiberoptic delivered, free running, pulsed Nd:YAG laser (; wavelength 1064nm. pulse duration $120{\mu}sec$, fiber diameter $320{{\mu}m}$) to cementum surfaces in triplicates of one experiment under the following lasing conditions: 1. stationary mode of fiber in contact to cementum surfaces without air-spray (; Group I )/with air-spray (; Group II), 2. unidirectional moving mode of fiber in contact to cementum surfaces under speed of 3mm-4mm/sec without air-spray (; Group III)/with air-spray (; Group IV), 3. energy per pulse (mJ/pulse) [; energy density ($J/cm^{2}$)] in order of 1.0W/10Hz (100J/pulse); $124J/cm^{2}$, 0.5W/10Hz (50mJ/pulse); $62J/cm^{2}$, 0.4W/10Hz (40mJ/pulse); $50J/cm^{2}$, 0.3W/10Hz (30mJ/pulse); $37J/cm^{2}$, 4. exposure time of 1 second. And the author applied the platinum coating on surfaces of cementum specimens, and evaluated the characteristics of ultrastructural change on surfaces of cementum using the scanning electron microscopy. In general the ultrastructural loss of cervical cementum irradiated under the same lasing condition of laser energy density occurred least in specimens of Group IV. And especially, the ultrastructural loss of cervical cementum irradiated under the laser energy density of $37J/cm^{2}$ almost did not occur in specimens of Group IV. Therefore, it is considered that the pulsed Nd:YAG laser should be applied with the lasing conditions of unidirectional moving mode of fiber in contact to cementum surfaces under speed of 3mm-4mm/sec with air-spray and of laser energy density within $37J/cm^{2}$ as an adjunctive modality of periodontal therapy of root planing without irreversible structural deterioration of cervical cementum.

• 한국전문물리치료학회지
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• 제13권3호
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• pp.33-40
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• 2006

The purpose of this study was to assess the effects of High-Voltage Pulsed Current (HVPC) and ultrasound on adjuvant-induced arthritis in rats. Adjuvant arthritis was induced in female Sprauge-Dawley rats by the subcutaneous injection of a single dose of $.1m{\ell}$ of Complete Freund's Adjuvant (CFA) (1 mg of Mycobacterium Butyricum suspended in $.1m{\ell}$ paraffin oil) into the right hind paw. A randomized, parallel-groups design of 24 subjects was used. All rats were randomly assigned to control (n=8), ultrasound (n=8), and HVPC (n=8) were compared with those of injured rats. The rats in the pulsed ultrasound group were treated at 1 MHz frequency with $.5W/cm^2$ intensity in 1:4 mode for 5 minutes per day. The rats in the HVPC group were treated at 120 pulses per second and $50{\mu}s$ phase duration, 20 mA intensity for 30 min per day. Treatment was done in the left and right hind limb for 2 weeks. We evaluated clinical, radiographic, hematologic and histopathologic findings before and after treatment and obtained the following results. 1. Edema of the right hind paw was more significantly reduced in the ultrasound and HVPC groups than the control group on days 9, 12, and 14 (p<.05). Edema of the left hind paw was more significantly reduced in ultrasound and HVPC groups than the control group on days 12, 14 (p<.05). 2. WBC counts of the ultrasound and HVPC groups as compared with the control group were becoming remarkably decreased after the treatment. 3. In radiologic findings, arthritis formation was seen according to the score of arthritis, which was the highest in the control group, upon the observation of radiographs of the left and right hind paws. However, no statistically significant difference was present in the score within three groups. 4. In the histopathologic findings, ultrasound and HVPC groups had effectively suppressed erosions of articular cartilage and inflammatory cell infiltrations. Therefore, the results of the study show that rats that were treated with the ultrasound and HVPC effectively suppressed adjuvant arthritis. However, no statistically significant difference was present between the ultrasound group and the HVPC group.

• Journal of Pharmaceutical Investigation
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• 제32권4호
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• pp.259-265
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• 2002

Piroxicam is one of the NSAID, which is used in the systemic and topical treatment of a variety of inflammatory conditions. Conventionally, for topical use, the drug is formulated in gel. We designed an phonophoretic drug delivery system to investigate the piroxicam permeability and the influence of ultrasound application (continuous mode, pulsed mode), frequency (1.0 MHz, 3.0 MHz) and intensity $(1.0\;w/cm^2,\;1.5\;w/cm^2,\;2.0\;w/cm^2)$ with 0.5% piroxicam gel. Per cutaneous absorption studies were performed in vitro models to determine the rate of drug absorption via the skin. Permeation study using hairless mouse skin was performed at $37^{\circ}C$ using buffered saline (pH 7.4, 10% propylene glycol solution) as the receptor solution. Anti-inflammatory activity was determined using carrageenan-induced foot edema model in rat. A pronounced effect of ultrasound on the skin absorption of the piroxicam was observed at all ultrasound energy level studied. Ultrasound was carried out for 10 hr. The highest permeation was observed at intensity of $2.0\;w/cm^2$, frequency of 1.0 MHz and continuous output. The inclusion of phonophoresis was found to improve significantly the skin permeation in vitro and the anti-inflammatory activity in vivo.

• Journal of Electrical Engineering and Technology
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• 제1권1호
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• pp.110-113
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• 2006

A high rate deposition sputtering process of magnesium oxide thin film in oxide mode has been developed using a 20 kW unipolar pulsed power supply. The power supply was operated at a maximum constant voltage of 500 V and a constant current of 40 A. The pulse repetition rate and the duty were changed in the ranges of $10\sim50$ kHz and $10\sim60%$, respectively. The deposition rate increased with rising incident power to the target. Maximum incident power to the magnesium target was obtained by the control of frequency, duty and current. The deposition rate of a moving state was 9 nm m/min at the average power of 1.5 kW. This result shows higher deposition rate than any other previous work involving reactive sputtering in oxide mode. The thickness uniformities over the entire substrate area of $982mm{\times}563mm$ were observed at the processing pressure of $2.8\sim9.5$ mTorr. The thickness distribution was improved at lower pressure. This technique is proposed for application to a high through-put sputtering system for plasma display panels.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.226-226
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• 2010

Boron Nitride (BN) doped GeSbTe films were grown by the ion beam sputtering deposition (IBSD). The in-situ sheet resistance data and the x-ray diffraction patterns showed the crystallization is suppressed due to the BN incorporation. The phase change speed in BN doped GeSbTe films were investigated using the static tester equipped with nanosecond pulsed laser. The phase change speed for BN doped GST films become faster than the corresponding values for an undoped GST film. The Johnson-Mehl-Avrami(JMA) plot and Avrami coefficient for laser crystallization showed that the change in growth mode during the laser crystallization is a most important factor for the phase change speed in the BN doped GST films. The JMA results and the atomic force microscopy (AFM) images indicate that the origin of the change in the crystalline growth mode is due to an increase in the number of initial nucleation sites which is produced by the incorporated BN. In addition, the retension properties for the laser writing/erasing are remarkably improved in BN doped GeSbTe films owing to the stability of the incorporated BN.